2010-01-27 13:01:08

by Stefani Seibold

Subject: [PATCH] enhanced reimplemention of the kfifo API

This is a complete reimplementation of the new kfifo API, which is now
really generic, type save and type definable.

The API is still stable, no code which use the current kfifo API must
be modified!

Here are the results of the text section usage:

Example 1:
kfifo_put/_get kfifo_in/out current kfifo
dynamic allocated 0x000002a8 0x00000291 0x00000299
in place 0x00000291 0x0000026e 0x00000273

kfifo.c new old
text section size 0x00000be5 0x000008b2

As you can see, kfifo_put/kfifo_get creates a little bit more code than
kfifo_in/kfifo_out, but it is much faster (the code is inline).

The code is complete hand crafted and optimized. The text section size is as
small as possible. You get all the fifo handling in only 3 kb. This includes
type safe fix size records, dynamic records and DMA handling.

This should be the final version. All requested features are implemented.

ChangeLog:

27.01.2010 renamed kfifo_sizeof into kfifo_esize
code refactoring: shrink foot print
fix bugs
changed all 0 pointer into NULL
fix a miss use in drivers/char/nozomi.c
enhanced DMA functions to handle a non continues fifo buffer (e.g. vmalloc)
reintroduced record dynamic handling as requested (tried to implemented it
separately, but this will double the code)
Sync with kernel 2.6.33-rc5
16.01.2010 Kicked away dynamic record handling. If anybody want it please let me know.
Add a esize field which represents the size of the element stored in
the fifo. This will increase the size of the fifo stucture by 4 bytes
but obtain a smaller code.
Generalized the kfifo.c funtions to handle byte and all other element
sizes in common functions.
Shrink the code size of kfifo.c from 2k to 1k
Code cleanup
15.01.2010 fix kfifo_dma_*() bugs
add a DMA usage exmaple
fix kfifo_free()
prevent creation of fifo with less then 2 entries
prevent a real in place fifo manipulation with kfifo_alloc(),
kfifo_init() or kfifo_free()
make INIT_KFIFO save with a dynamic allocated fifo
14.01.2010 Change the size field of the fifo structure into a mask field, which
is size - 1. This will save some instructions
Make the basic structure mode generic. Add a data pointer and mask
field, also for real in place fifo, because the extra function parameter
passing of the data pointer and and the fifo size was to costly
Change all internal functions to work with the generic base structure
Optimized the kfifo_put and kfifo_get macros to prevent an indirection
Code cleanup
Bug fixes in kfifo_dma_* macros
Update examples
Sync with kernel 2.6.33-rc4
06.01.2010 Add a note about locking: clarify when locking is needed
Fix byte stream example
Remove unnecessary typedefs
Make checkpatch.pl clean: one error left, but there is no way to
solve this...
28.12.2009 Sanitize kfifo_*_user() error handling (suggested by Andi Kleen)
kfifo_from_user() and kfifo_to_user() will now return an error
code and the number of copied bytes will be stored in a variable
passed as pointer
Make patch readable
Update examples
Fix a typo
27.12.2009 Sync with kernel 2.6.33-rc2
Introduce new kfifo_initialized macro (suggested by Andi Kleen)
Renamed kfifo_peek into kfifo_peek_len
Introduce new kfifo_peek macro (suggest by Andi Kleen)
Introduce new kfifo_out_peek macro (suggested by Andi Kleen)
Fix broken kernel-doc notation
Fix samples
21.12.2009 Fix checkpatch.pl, fix samples
20.12.2009 Bug fixing
Fix samples
19.12.2009 First draft
13.12.2009 First implementation of a type safe fifo implementation, called kqueue

There are different types of a fifo which can not handled in C without a
lot of overhead. So i decided to write the API as a set of macros, which
is the only way to do a kind of template meta programming without C++.
This macros handles the different types of fifos in a transparent way.

There are a lot of benefits:

- Compile time handling of the different fifo types
- Better performance (a save put or get of an integer does only generate
9 assembly instructions on a x86)
- Type save
- Cleaner interface, the additional kfifo_..._rec() functions are gone
- Easier to use
- Less error prone
- Different types of fifos: it is now possible to define a int fifo or
any other type. See below for an example.
- Smaller footprint for none byte type fifos
- No need of creating a second hidden variable, like in the old DEFINE_KFIFO

The API was not changed.

There are now real in place fifos where the data space is a part of the
structure. There is no need for an extra indirection to access the data.

The fifo needs now 20 byte plus the fifo space. Dynamic assigned or allocated
does create a little bit more code.

Most of the macros code will be optimized away and simple generate a
function call. Only the really small one generates inline code.

Additional you can now create fifos for any data type, not only the
"unsigned char" byte streamed fifos.

There is also a new kfifo_put and kfifo_get function, to handle a single
element in a fifo. This macros generates inline code, which is lit bit
larger but faster.

Here are the examples how to use it:

Example 1: an integer fifo

#include "kfifo.h"

#define FIFO_SIZE 32

#define DYNAMIC
#ifdef DYNAMIC
static DECLARE_KFIFO_PTR(test, int);
#else
static DECLARE_KFIFO(test, int, FIFO_SIZE);
#endif

int testfunc(void)
{
int i;
int buf[6];
unsigned int ret;
unsigned int copied;

#ifdef DYNAMIC
if (kfifo_alloc(&test, FIFO_SIZE, 0)) {
printk("error kfifo_alloc\n");
return 1;
}
#else
INIT_KFIFO(test);
#endif

printk("int fifo test start\n");

if (kfifo_initialized(&test))
printk("fifo is initalized\n");

for(i = 0; i != 10; i++)
kfifo_put(&test, &i);

printk("queue peek: %u\n", kfifo_peek_len(&test));

ret = kfifo_to_user(&test, buf, kfifo_sizeof(&test) * 2, &copied);
printk("ret: %d %u\n", ret, copied);
ret = kfifo_from_user(&test, buf, copied, &copied);
printk("ret: %d %u\n", ret, copied);
ret = kfifo_out(&test, buf, 1);
printk("ret: %d\n", ret);
ret = kfifo_in(&test, buf, 1);
printk("ret: %d\n", ret);

for(i = 20; i != 30; i++)
kfifo_put(&test, &i);

printk("queue len: %u\n", kfifo_len(&test));

if (kfifo_peek(&test, &i))
printk("%d\n", i);

while(kfifo_get(&test, &i))
printk("%d ", i);
printk("\n");

return 0;
}


Example 2: DMA usage

#include "kfifo.h"

#define FIFO_SIZE 32

static struct kfifo fifo;

int testfunc(void)
{
int i;
unsigned int ret;
/* kfifo_dma_* will never return more than two sgl entries */
struct scatterlist sg[2];

printk("DMA fifo test start\n");

if (kfifo_alloc(&fifo, FIFO_SIZE, 0)) {
printk("error kfifo_alloc\n");
return 1;
}

printk("queue size: %u\n", kfifo_size(&fifo));

kfifo_in(&fifo, "test", 4);

for(i = 0; i != 9; i++)
kfifo_put(&fifo, &i);

/* kick away first byte */
kfifo_get(&fifo, &i);

printk("queue len: %u\n", kfifo_len(&fifo));

ret = kfifo_dma_in_prepare(&fifo, sg, ARRAY_SIZE(sg), FIFO_SIZE);
printk("DMA sgl entries: %d\n", ret);

/* if 0 was returned, fifo is full and no sgl was created */
if (ret) {
printk("scatterlist for receive:\n");
for (i = 0; i < ARRAY_SIZE(sg); i++) {
printk("sg[%d] -> page_link 0x%.8lx offset 0x%.8x len 0x%.8x\n",
i, sg[i].page_link, sg[i].offset, sg[i].length);

if (sg_is_last(&sg[i]))
break;
}

/* but here your code to setup and exectute the dma operation */
/* ... */

/* example: zero bytes received */
ret = 0;

/* finish the dma operation and update the received data */
kfifo_dma_in_finish(&fifo, ret);
}

ret = kfifo_dma_out_prepare(&fifo, sg, ARRAY_SIZE(sg), 8);
printk("DMA sgl entries: %d\n", ret);

/* if 0 was returned, no data was available and no sgl was created */
if (ret) {
printk("scatterlist for transmit:\n");
for (i = 0; i < ARRAY_SIZE(sg); i++) {
printk("sg[%d] -> page_link 0x%.8lx offset 0x%.8x len 0x%.8x\n",
i, sg[i].page_link, sg[i].offset, sg[i].length);

if (sg_is_last(&sg[i]))
break;
}

/* but here your code to setup and exectute the dma operation */
/* ... */

/* example: 5 bytes transmitted */
ret = 5;

/* finish the dma operation and update the transmitted data */
kfifo_dma_out_finish(&fifo, ret);
}

printk("queue len: %u\n", kfifo_len(&fifo));

return 0;
}


Example 3: a bytes stream fifo

#include "kfifo.h"

#define FIFO_SIZE 32

//#define DYNAMIC
#ifdef DYNAMIC
static struct kfifo test[1];
#else
static DECLARE_KFIFO(test[1], unsigned char, FIFO_SIZE);
#endif

int testfunc(void)
{
unsigned char buf[6];
unsigned char i;
unsigned int ret;
unsigned int copied;

printk("byte stream fifo test start\n");

#ifdef DYNAMIC
if (kfifo_alloc(test, FIFO_SIZE, 0)) {
printk("error kfifo_alloc\n");
return 1;
}
#else
INIT_KFIFO(test[0]);
#endif

printk("queue size: %u\n", kfifo_size(test));

kfifo_in(test, "hello", 5);

for(i = 0; i != 9; i++)
kfifo_put(test, &i);

printk("queue peek: %u\n", kfifo_peek_len(test));

i = kfifo_out(test, buf, 5);
printk("buf: %.*s\n", i, buf);

ret = kfifo_to_user(test, buf, sizeof(int), &copied);
printk("ret: %d %u\n", ret, copied);
ret = kfifo_from_user(test, buf, copied, &copied);
printk("ret: %d %u\n", ret, copied);

ret = kfifo_out(test, buf, 2);
printk("ret: %d\n", ret);
ret = kfifo_in(test, buf, ret);
printk("ret: %d\n", ret);

printk("queue len: %u\n", kfifo_len(test));

for(i = 20; kfifo_put(test, &i); i++)
;

while(kfifo_get(test, &i))
printk("%d ", i);
printk("\n");

return 0;
}


Example 4: a dynamic record fifo

#include "kfifo.h"

#define FIFO_SIZE 128

#define DYNAMIC
#ifdef DYNAMIC
struct kfifo_rec_ptr_1 test[1];

#else
typedef STRUCT_KFIFO_REC_1(FIFO_SIZE) mytest;

static mytest test[1];
#endif

int testfunc(void)
{
struct { unsigned char buf[6]; } hello = { "hello" };
unsigned int i;
char buf[100];
unsigned int ret;
unsigned int copied = 0;

printk("record fifo test start\n");

if (kfifo_alloc(test, FIFO_SIZE, 0)) {
printk("error kfifo_alloc\n");
return 1;
}
printk("queue size: %u\n", kfifo_size(test));

kfifo_in(test, &hello, sizeof(hello));

printk("queue peek: %u\n", kfifo_peek_len(test));

for(i = 0; i < 10; i++) {
memset(buf,'a' + i, i + 1);
kfifo_in(test, buf, i + 1);
}

ret = kfifo_to_user(test, buf, sizeof(buf), &copied);
printk("ret: %d %u\n", ret, copied);
ret = kfifo_from_user(test, buf, copied, &copied);
printk("ret: %d %u\n", ret, copied);

printk("queue len: %u\n", kfifo_len(test));

ret = kfifo_peek(test, buf);
if (ret)
printk("%.*s\n", ret, buf);

while(!kfifo_is_empty(test)) {
ret = kfifo_out(test, buf, sizeof(buf));
printk("%.*s\n", ret, buf);
}

return 0;
}


I know that this kind of macros are very sophisticated and not easy to
maintain. But i have all tested and it works as expected. I analyzed the
output of the compiler and for the x86 the code is as good as hand
written assembler code. For the byte stream fifo the generate code is exact
the same as with the current kfifo implementation. For all other types of
fifos the code is smaller before, because the interface is easier to use.

The main goal was to provide an API which is very intuitive, save and easy
to use. So linux will get now a powerful fifo API which provides all what
a developer needs. This will save in the future a lot of kernel space, since
there is no need to write an own implementation. Most of the device driver
developers need a fifo, and also deep kernel development will gain benefit
from this API.

You can download the test code at http://www.seibold.net/kfifo.tgz

The patch-set is against linux 2.6.33-rc5. This code is ready to merge into
the mm tree or linux next. Please review it and merge.

Stefani

Signed-off-by: Stefani Seibold <[email protected]>
---
linux-2.6.33-rc5.dummy/include/linux/kfifo.h | 616 --------------------
linux-2.6.33-rc5.dummy/kernel/kfifo.c | 443 --------------
linux-2.6.33-rc5.new/drivers/char/nozomi.c | 2
linux-2.6.33-rc5.new/include/linux/kfifo.h | 812 +++++++++++++++++++++++++++
linux-2.6.33-rc5.new/kernel/kfifo.c | 583 +++++++++++++++++++
5 files changed, 1396 insertions(+), 1060 deletions(-)

diff -u -N -r -p linux-2.6.33-rc5.orig/include/linux/kfifo.h linux-2.6.33-rc5.dummy/include/linux/kfifo.h
--- linux-2.6.33-rc5.orig/include/linux/kfifo.h 2010-01-27 12:48:15.885017143 +0100
+++ linux-2.6.33-rc5.dummy/include/linux/kfifo.h 1970-01-01 01:00:00.000000000 +0100
@@ -1,616 +0,0 @@
-/*
- * A generic kernel FIFO implementation.
- *
- * Copyright (C) 2009 Stefani Seibold <[email protected]>
- * Copyright (C) 2004 Stelian Pop <[email protected]>
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
- *
- */
-
-/*
- * Howto porting drivers to the new generic fifo API:
- *
- * - Modify the declaration of the "struct kfifo *" object into a
- * in-place "struct kfifo" object
- * - Init the in-place object with kfifo_alloc() or kfifo_init()
- * Note: The address of the in-place "struct kfifo" object must be
- * passed as the first argument to this functions
- * - Replace the use of __kfifo_put into kfifo_in and __kfifo_get
- * into kfifo_out
- * - Replace the use of kfifo_put into kfifo_in_locked and kfifo_get
- * into kfifo_out_locked
- * Note: the spinlock pointer formerly passed to kfifo_init/kfifo_alloc
- * must be passed now to the kfifo_in_locked and kfifo_out_locked
- * as the last parameter.
- * - All formerly name __kfifo_* functions has been renamed into kfifo_*
- */
-
-#ifndef _LINUX_KFIFO_H
-#define _LINUX_KFIFO_H
-
-#include <linux/kernel.h>
-#include <linux/spinlock.h>
-
-struct kfifo {
- unsigned char *buffer; /* the buffer holding the data */
- unsigned int size; /* the size of the allocated buffer */
- unsigned int in; /* data is added at offset (in % size) */
- unsigned int out; /* data is extracted from off. (out % size) */
-};
-
-/*
- * Macros for declaration and initialization of the kfifo datatype
- */
-
-/* helper macro */
-#define __kfifo_initializer(s, b) \
- (struct kfifo) { \
- .size = s, \
- .in = 0, \
- .out = 0, \
- .buffer = b \
- }
-
-/**
- * DECLARE_KFIFO - macro to declare a kfifo and the associated buffer
- * @name: name of the declared kfifo datatype
- * @size: size of the fifo buffer. Must be a power of two.
- *
- * Note1: the macro can be used inside struct or union declaration
- * Note2: the macro creates two objects:
- * A kfifo object with the given name and a buffer for the kfifo
- * object named name##kfifo_buffer
- */
-#define DECLARE_KFIFO(name, size) \
-union { \
- struct kfifo name; \
- unsigned char name##kfifo_buffer[size + sizeof(struct kfifo)]; \
-}
-
-/**
- * INIT_KFIFO - Initialize a kfifo declared by DECLARE_KFIFO
- * @name: name of the declared kfifo datatype
- */
-#define INIT_KFIFO(name) \
- name = __kfifo_initializer(sizeof(name##kfifo_buffer) - \
- sizeof(struct kfifo), name##kfifo_buffer)
-
-/**
- * DEFINE_KFIFO - macro to define and initialize a kfifo
- * @name: name of the declared kfifo datatype
- * @size: size of the fifo buffer. Must be a power of two.
- *
- * Note1: the macro can be used for global and local kfifo data type variables
- * Note2: the macro creates two objects:
- * A kfifo object with the given name and a buffer for the kfifo
- * object named name##kfifo_buffer
- */
-#define DEFINE_KFIFO(name, size) \
- unsigned char name##kfifo_buffer[size]; \
- struct kfifo name = __kfifo_initializer(size, name##kfifo_buffer)
-
-#undef __kfifo_initializer
-
-extern void kfifo_init(struct kfifo *fifo, void *buffer,
- unsigned int size);
-extern __must_check int kfifo_alloc(struct kfifo *fifo, unsigned int size,
- gfp_t gfp_mask);
-extern void kfifo_free(struct kfifo *fifo);
-extern unsigned int kfifo_in(struct kfifo *fifo,
- const void *from, unsigned int len);
-extern __must_check unsigned int kfifo_out(struct kfifo *fifo,
- void *to, unsigned int len);
-extern __must_check unsigned int kfifo_out_peek(struct kfifo *fifo,
- void *to, unsigned int len, unsigned offset);
-
-/**
- * kfifo_initialized - Check if kfifo is initialized.
- * @fifo: fifo to check
- * Return %true if FIFO is initialized, otherwise %false.
- * Assumes the fifo was 0 before.
- */
-static inline bool kfifo_initialized(struct kfifo *fifo)
-{
- return fifo->buffer != 0;
-}
-
-/**
- * kfifo_reset - removes the entire FIFO contents
- * @fifo: the fifo to be emptied.
- */
-static inline void kfifo_reset(struct kfifo *fifo)
-{
- fifo->in = fifo->out = 0;
-}
-
-/**
- * kfifo_reset_out - skip FIFO contents
- * @fifo: the fifo to be emptied.
- */
-static inline void kfifo_reset_out(struct kfifo *fifo)
-{
- smp_mb();
- fifo->out = fifo->in;
-}
-
-/**
- * kfifo_size - returns the size of the fifo in bytes
- * @fifo: the fifo to be used.
- */
-static inline __must_check unsigned int kfifo_size(struct kfifo *fifo)
-{
- return fifo->size;
-}
-
-/**
- * kfifo_len - returns the number of used bytes in the FIFO
- * @fifo: the fifo to be used.
- */
-static inline unsigned int kfifo_len(struct kfifo *fifo)
-{
- register unsigned int out;
-
- out = fifo->out;
- smp_rmb();
- return fifo->in - out;
-}
-
-/**
- * kfifo_is_empty - returns true if the fifo is empty
- * @fifo: the fifo to be used.
- */
-static inline __must_check int kfifo_is_empty(struct kfifo *fifo)
-{
- return fifo->in == fifo->out;
-}
-
-/**
- * kfifo_is_full - returns true if the fifo is full
- * @fifo: the fifo to be used.
- */
-static inline __must_check int kfifo_is_full(struct kfifo *fifo)
-{
- return kfifo_len(fifo) == kfifo_size(fifo);
-}
-
-/**
- * kfifo_avail - returns the number of bytes available in the FIFO
- * @fifo: the fifo to be used.
- */
-static inline __must_check unsigned int kfifo_avail(struct kfifo *fifo)
-{
- return kfifo_size(fifo) - kfifo_len(fifo);
-}
-
-/**
- * kfifo_in_locked - puts some data into the FIFO using a spinlock for locking
- * @fifo: the fifo to be used.
- * @from: the data to be added.
- * @n: the length of the data to be added.
- * @lock: pointer to the spinlock to use for locking.
- *
- * This function copies at most @len bytes from the @from buffer into
- * the FIFO depending on the free space, and returns the number of
- * bytes copied.
- */
-static inline unsigned int kfifo_in_locked(struct kfifo *fifo,
- const void *from, unsigned int n, spinlock_t *lock)
-{
- unsigned long flags;
- unsigned int ret;
-
- spin_lock_irqsave(lock, flags);
-
- ret = kfifo_in(fifo, from, n);
-
- spin_unlock_irqrestore(lock, flags);
-
- return ret;
-}
-
-/**
- * kfifo_out_locked - gets some data from the FIFO using a spinlock for locking
- * @fifo: the fifo to be used.
- * @to: where the data must be copied.
- * @n: the size of the destination buffer.
- * @lock: pointer to the spinlock to use for locking.
- *
- * This function copies at most @len bytes from the FIFO into the
- * @to buffer and returns the number of copied bytes.
- */
-static inline __must_check unsigned int kfifo_out_locked(struct kfifo *fifo,
- void *to, unsigned int n, spinlock_t *lock)
-{
- unsigned long flags;
- unsigned int ret;
-
- spin_lock_irqsave(lock, flags);
-
- ret = kfifo_out(fifo, to, n);
-
- spin_unlock_irqrestore(lock, flags);
-
- return ret;
-}
-
-extern void kfifo_skip(struct kfifo *fifo, unsigned int len);
-
-extern __must_check int kfifo_from_user(struct kfifo *fifo,
- const void __user *from, unsigned int n, unsigned *lenout);
-
-extern __must_check int kfifo_to_user(struct kfifo *fifo,
- void __user *to, unsigned int n, unsigned *lenout);
-
-/*
- * __kfifo_add_out internal helper function for updating the out offset
- */
-static inline void __kfifo_add_out(struct kfifo *fifo,
- unsigned int off)
-{
- smp_mb();
- fifo->out += off;
-}
-
-/*
- * __kfifo_add_in internal helper function for updating the in offset
- */
-static inline void __kfifo_add_in(struct kfifo *fifo,
- unsigned int off)
-{
- smp_wmb();
- fifo->in += off;
-}
-
-/*
- * __kfifo_off internal helper function for calculating the index of a
- * given offeset
- */
-static inline unsigned int __kfifo_off(struct kfifo *fifo, unsigned int off)
-{
- return off & (fifo->size - 1);
-}
-
-/*
- * __kfifo_peek_n internal helper function for determinate the length of
- * the next record in the fifo
- */
-static inline unsigned int __kfifo_peek_n(struct kfifo *fifo,
- unsigned int recsize)
-{
-#define __KFIFO_GET(fifo, off, shift) \
- ((fifo)->buffer[__kfifo_off((fifo), (fifo)->out+(off))] << (shift))
-
- unsigned int l;
-
- l = __KFIFO_GET(fifo, 0, 0);
-
- if (--recsize)
- l |= __KFIFO_GET(fifo, 1, 8);
-
- return l;
-#undef __KFIFO_GET
-}
-
-/*
- * __kfifo_poke_n internal helper function for storing the length of
- * the next record into the fifo
- */
-static inline void __kfifo_poke_n(struct kfifo *fifo,
- unsigned int recsize, unsigned int n)
-{
-#define __KFIFO_PUT(fifo, off, val, shift) \
- ( \
- (fifo)->buffer[__kfifo_off((fifo), (fifo)->in+(off))] = \
- (unsigned char)((val) >> (shift)) \
- )
-
- __KFIFO_PUT(fifo, 0, n, 0);
-
- if (--recsize)
- __KFIFO_PUT(fifo, 1, n, 8);
-#undef __KFIFO_PUT
-}
-
-/*
- * __kfifo_in_... internal functions for put date into the fifo
- * do not call it directly, use kfifo_in_rec() instead
- */
-extern unsigned int __kfifo_in_n(struct kfifo *fifo,
- const void *from, unsigned int n, unsigned int recsize);
-
-extern unsigned int __kfifo_in_generic(struct kfifo *fifo,
- const void *from, unsigned int n, unsigned int recsize);
-
-static inline unsigned int __kfifo_in_rec(struct kfifo *fifo,
- const void *from, unsigned int n, unsigned int recsize)
-{
- unsigned int ret;
-
- ret = __kfifo_in_n(fifo, from, n, recsize);
-
- if (likely(ret == 0)) {
- if (recsize)
- __kfifo_poke_n(fifo, recsize, n);
- __kfifo_add_in(fifo, n + recsize);
- }
- return ret;
-}
-
-/**
- * kfifo_in_rec - puts some record data into the FIFO
- * @fifo: the fifo to be used.
- * @from: the data to be added.
- * @n: the length of the data to be added.
- * @recsize: size of record field
- *
- * This function copies @n bytes from the @from into the FIFO and returns
- * the number of bytes which cannot be copied.
- * A returned value greater than the @n value means that the record doesn't
- * fit into the buffer.
- *
- * Note that with only one concurrent reader and one concurrent
- * writer, you don't need extra locking to use these functions.
- */
-static inline __must_check unsigned int kfifo_in_rec(struct kfifo *fifo,
- void *from, unsigned int n, unsigned int recsize)
-{
- if (!__builtin_constant_p(recsize))
- return __kfifo_in_generic(fifo, from, n, recsize);
- return __kfifo_in_rec(fifo, from, n, recsize);
-}
-
-/*
- * __kfifo_out_... internal functions for get date from the fifo
- * do not call it directly, use kfifo_out_rec() instead
- */
-extern unsigned int __kfifo_out_n(struct kfifo *fifo,
- void *to, unsigned int reclen, unsigned int recsize);
-
-extern unsigned int __kfifo_out_generic(struct kfifo *fifo,
- void *to, unsigned int n,
- unsigned int recsize, unsigned int *total);
-
-static inline unsigned int __kfifo_out_rec(struct kfifo *fifo,
- void *to, unsigned int n, unsigned int recsize,
- unsigned int *total)
-{
- unsigned int l;
-
- if (!recsize) {
- l = n;
- if (total)
- *total = l;
- } else {
- l = __kfifo_peek_n(fifo, recsize);
- if (total)
- *total = l;
- if (n < l)
- return l;
- }
-
- return __kfifo_out_n(fifo, to, l, recsize);
-}
-
-/**
- * kfifo_out_rec - gets some record data from the FIFO
- * @fifo: the fifo to be used.
- * @to: where the data must be copied.
- * @n: the size of the destination buffer.
- * @recsize: size of record field
- * @total: pointer where the total number of to copied bytes should stored
- *
- * This function copies at most @n bytes from the FIFO to @to and returns the
- * number of bytes which cannot be copied.
- * A returned value greater than the @n value means that the record doesn't
- * fit into the @to buffer.
- *
- * Note that with only one concurrent reader and one concurrent
- * writer, you don't need extra locking to use these functions.
- */
-static inline __must_check unsigned int kfifo_out_rec(struct kfifo *fifo,
- void *to, unsigned int n, unsigned int recsize,
- unsigned int *total)
-
-{
- if (!__builtin_constant_p(recsize))
- return __kfifo_out_generic(fifo, to, n, recsize, total);
- return __kfifo_out_rec(fifo, to, n, recsize, total);
-}
-
-/*
- * __kfifo_from_user_... internal functions for transfer from user space into
- * the fifo. do not call it directly, use kfifo_from_user_rec() instead
- */
-extern unsigned int __kfifo_from_user_n(struct kfifo *fifo,
- const void __user *from, unsigned int n, unsigned int recsize);
-
-extern unsigned int __kfifo_from_user_generic(struct kfifo *fifo,
- const void __user *from, unsigned int n, unsigned int recsize);
-
-static inline unsigned int __kfifo_from_user_rec(struct kfifo *fifo,
- const void __user *from, unsigned int n, unsigned int recsize)
-{
- unsigned int ret;
-
- ret = __kfifo_from_user_n(fifo, from, n, recsize);
-
- if (likely(ret == 0)) {
- if (recsize)
- __kfifo_poke_n(fifo, recsize, n);
- __kfifo_add_in(fifo, n + recsize);
- }
- return ret;
-}
-
-/**
- * kfifo_from_user_rec - puts some data from user space into the FIFO
- * @fifo: the fifo to be used.
- * @from: pointer to the data to be added.
- * @n: the length of the data to be added.
- * @recsize: size of record field
- *
- * This function copies @n bytes from the @from into the
- * FIFO and returns the number of bytes which cannot be copied.
- *
- * If the returned value is equal or less the @n value, the copy_from_user()
- * functions has failed. Otherwise the record doesn't fit into the buffer.
- *
- * Note that with only one concurrent reader and one concurrent
- * writer, you don't need extra locking to use these functions.
- */
-static inline __must_check unsigned int kfifo_from_user_rec(struct kfifo *fifo,
- const void __user *from, unsigned int n, unsigned int recsize)
-{
- if (!__builtin_constant_p(recsize))
- return __kfifo_from_user_generic(fifo, from, n, recsize);
- return __kfifo_from_user_rec(fifo, from, n, recsize);
-}
-
-/*
- * __kfifo_to_user_... internal functions for transfer fifo data into user space
- * do not call it directly, use kfifo_to_user_rec() instead
- */
-extern unsigned int __kfifo_to_user_n(struct kfifo *fifo,
- void __user *to, unsigned int n, unsigned int reclen,
- unsigned int recsize);
-
-extern unsigned int __kfifo_to_user_generic(struct kfifo *fifo,
- void __user *to, unsigned int n, unsigned int recsize,
- unsigned int *total);
-
-static inline unsigned int __kfifo_to_user_rec(struct kfifo *fifo,
- void __user *to, unsigned int n,
- unsigned int recsize, unsigned int *total)
-{
- unsigned int l;
-
- if (!recsize) {
- l = n;
- if (total)
- *total = l;
- } else {
- l = __kfifo_peek_n(fifo, recsize);
- if (total)
- *total = l;
- if (n < l)
- return l;
- }
-
- return __kfifo_to_user_n(fifo, to, n, l, recsize);
-}
-
-/**
- * kfifo_to_user_rec - gets data from the FIFO and write it to user space
- * @fifo: the fifo to be used.
- * @to: where the data must be copied.
- * @n: the size of the destination buffer.
- * @recsize: size of record field
- * @total: pointer where the total number of to copied bytes should stored
- *
- * This function copies at most @n bytes from the FIFO to the @to.
- * In case of an error, the function returns the number of bytes which cannot
- * be copied.
- * If the returned value is equal or less the @n value, the copy_to_user()
- * functions has failed. Otherwise the record doesn't fit into the @to buffer.
- *
- * Note that with only one concurrent reader and one concurrent
- * writer, you don't need extra locking to use these functions.
- */
-static inline __must_check unsigned int kfifo_to_user_rec(struct kfifo *fifo,
- void __user *to, unsigned int n, unsigned int recsize,
- unsigned int *total)
-{
- if (!__builtin_constant_p(recsize))
- return __kfifo_to_user_generic(fifo, to, n, recsize, total);
- return __kfifo_to_user_rec(fifo, to, n, recsize, total);
-}
-
-/*
- * __kfifo_peek_... internal functions for peek into the next fifo record
- * do not call it directly, use kfifo_peek_rec() instead
- */
-extern unsigned int __kfifo_peek_generic(struct kfifo *fifo,
- unsigned int recsize);
-
-/**
- * kfifo_peek_rec - gets the size of the next FIFO record data
- * @fifo: the fifo to be used.
- * @recsize: size of record field
- *
- * This function returns the size of the next FIFO record in number of bytes
- */
-static inline __must_check unsigned int kfifo_peek_rec(struct kfifo *fifo,
- unsigned int recsize)
-{
- if (!__builtin_constant_p(recsize))
- return __kfifo_peek_generic(fifo, recsize);
- if (!recsize)
- return kfifo_len(fifo);
- return __kfifo_peek_n(fifo, recsize);
-}
-
-/*
- * __kfifo_skip_... internal functions for skip the next fifo record
- * do not call it directly, use kfifo_skip_rec() instead
- */
-extern void __kfifo_skip_generic(struct kfifo *fifo, unsigned int recsize);
-
-static inline void __kfifo_skip_rec(struct kfifo *fifo,
- unsigned int recsize)
-{
- unsigned int l;
-
- if (recsize) {
- l = __kfifo_peek_n(fifo, recsize);
-
- if (l + recsize <= kfifo_len(fifo)) {
- __kfifo_add_out(fifo, l + recsize);
- return;
- }
- }
- kfifo_reset_out(fifo);
-}
-
-/**
- * kfifo_skip_rec - skip the next fifo out record
- * @fifo: the fifo to be used.
- * @recsize: size of record field
- *
- * This function skips the next FIFO record
- */
-static inline void kfifo_skip_rec(struct kfifo *fifo,
- unsigned int recsize)
-{
- if (!__builtin_constant_p(recsize))
- __kfifo_skip_generic(fifo, recsize);
- else
- __kfifo_skip_rec(fifo, recsize);
-}
-
-/**
- * kfifo_avail_rec - returns the number of bytes available in a record FIFO
- * @fifo: the fifo to be used.
- * @recsize: size of record field
- */
-static inline __must_check unsigned int kfifo_avail_rec(struct kfifo *fifo,
- unsigned int recsize)
-{
- unsigned int l = kfifo_size(fifo) - kfifo_len(fifo);
-
- return (l > recsize) ? l - recsize : 0;
-}
-
-#endif
diff -u -N -r -p linux-2.6.33-rc5.orig/kernel/kfifo.c linux-2.6.33-rc5.dummy/kernel/kfifo.c
--- linux-2.6.33-rc5.orig/kernel/kfifo.c 2010-01-27 12:48:17.413892894 +0100
+++ linux-2.6.33-rc5.dummy/kernel/kfifo.c 1970-01-01 01:00:00.000000000 +0100
@@ -1,443 +0,0 @@
-/*
- * A generic kernel FIFO implementation.
- *
- * Copyright (C) 2009 Stefani Seibold <[email protected]>
- * Copyright (C) 2004 Stelian Pop <[email protected]>
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
- *
- */
-
-#include <linux/kernel.h>
-#include <linux/module.h>
-#include <linux/slab.h>
-#include <linux/err.h>
-#include <linux/kfifo.h>
-#include <linux/log2.h>
-#include <linux/uaccess.h>
-
-static void _kfifo_init(struct kfifo *fifo, void *buffer,
- unsigned int size)
-{
- fifo->buffer = buffer;
- fifo->size = size;
-
- kfifo_reset(fifo);
-}
-
-/**
- * kfifo_init - initialize a FIFO using a preallocated buffer
- * @fifo: the fifo to assign the buffer
- * @buffer: the preallocated buffer to be used.
- * @size: the size of the internal buffer, this has to be a power of 2.
- *
- */
-void kfifo_init(struct kfifo *fifo, void *buffer, unsigned int size)
-{
- /* size must be a power of 2 */
- BUG_ON(!is_power_of_2(size));
-
- _kfifo_init(fifo, buffer, size);
-}
-EXPORT_SYMBOL(kfifo_init);
-
-/**
- * kfifo_alloc - allocates a new FIFO internal buffer
- * @fifo: the fifo to assign then new buffer
- * @size: the size of the buffer to be allocated, this have to be a power of 2.
- * @gfp_mask: get_free_pages mask, passed to kmalloc()
- *
- * This function dynamically allocates a new fifo internal buffer
- *
- * The size will be rounded-up to a power of 2.
- * The buffer will be release with kfifo_free().
- * Return 0 if no error, otherwise the an error code
- */
-int kfifo_alloc(struct kfifo *fifo, unsigned int size, gfp_t gfp_mask)
-{
- unsigned char *buffer;
-
- /*
- * round up to the next power of 2, since our 'let the indices
- * wrap' technique works only in this case.
- */
- if (!is_power_of_2(size)) {
- BUG_ON(size > 0x80000000);
- size = roundup_pow_of_two(size);
- }
-
- buffer = kmalloc(size, gfp_mask);
- if (!buffer) {
- _kfifo_init(fifo, 0, 0);
- return -ENOMEM;
- }
-
- _kfifo_init(fifo, buffer, size);
-
- return 0;
-}
-EXPORT_SYMBOL(kfifo_alloc);
-
-/**
- * kfifo_free - frees the FIFO internal buffer
- * @fifo: the fifo to be freed.
- */
-void kfifo_free(struct kfifo *fifo)
-{
- kfree(fifo->buffer);
-}
-EXPORT_SYMBOL(kfifo_free);
-
-/**
- * kfifo_skip - skip output data
- * @fifo: the fifo to be used.
- * @len: number of bytes to skip
- */
-void kfifo_skip(struct kfifo *fifo, unsigned int len)
-{
- if (len < kfifo_len(fifo)) {
- __kfifo_add_out(fifo, len);
- return;
- }
- kfifo_reset_out(fifo);
-}
-EXPORT_SYMBOL(kfifo_skip);
-
-static inline void __kfifo_in_data(struct kfifo *fifo,
- const void *from, unsigned int len, unsigned int off)
-{
- unsigned int l;
-
- /*
- * Ensure that we sample the fifo->out index -before- we
- * start putting bytes into the kfifo.
- */
-
- smp_mb();
-
- off = __kfifo_off(fifo, fifo->in + off);
-
- /* first put the data starting from fifo->in to buffer end */
- l = min(len, fifo->size - off);
- memcpy(fifo->buffer + off, from, l);
-
- /* then put the rest (if any) at the beginning of the buffer */
- memcpy(fifo->buffer, from + l, len - l);
-}
-
-static inline void __kfifo_out_data(struct kfifo *fifo,
- void *to, unsigned int len, unsigned int off)
-{
- unsigned int l;
-
- /*
- * Ensure that we sample the fifo->in index -before- we
- * start removing bytes from the kfifo.
- */
-
- smp_rmb();
-
- off = __kfifo_off(fifo, fifo->out + off);
-
- /* first get the data from fifo->out until the end of the buffer */
- l = min(len, fifo->size - off);
- memcpy(to, fifo->buffer + off, l);
-
- /* then get the rest (if any) from the beginning of the buffer */
- memcpy(to + l, fifo->buffer, len - l);
-}
-
-static inline int __kfifo_from_user_data(struct kfifo *fifo,
- const void __user *from, unsigned int len, unsigned int off,
- unsigned *lenout)
-{
- unsigned int l;
- int ret;
-
- /*
- * Ensure that we sample the fifo->out index -before- we
- * start putting bytes into the kfifo.
- */
-
- smp_mb();
-
- off = __kfifo_off(fifo, fifo->in + off);
-
- /* first put the data starting from fifo->in to buffer end */
- l = min(len, fifo->size - off);
- ret = copy_from_user(fifo->buffer + off, from, l);
- if (unlikely(ret)) {
- *lenout = ret;
- return -EFAULT;
- }
- *lenout = l;
-
- /* then put the rest (if any) at the beginning of the buffer */
- ret = copy_from_user(fifo->buffer, from + l, len - l);
- *lenout += ret ? ret : len - l;
- return ret ? -EFAULT : 0;
-}
-
-static inline int __kfifo_to_user_data(struct kfifo *fifo,
- void __user *to, unsigned int len, unsigned int off, unsigned *lenout)
-{
- unsigned int l;
- int ret;
-
- /*
- * Ensure that we sample the fifo->in index -before- we
- * start removing bytes from the kfifo.
- */
-
- smp_rmb();
-
- off = __kfifo_off(fifo, fifo->out + off);
-
- /* first get the data from fifo->out until the end of the buffer */
- l = min(len, fifo->size - off);
- ret = copy_to_user(to, fifo->buffer + off, l);
- *lenout = l;
- if (unlikely(ret)) {
- *lenout -= ret;
- return -EFAULT;
- }
-
- /* then get the rest (if any) from the beginning of the buffer */
- len -= l;
- ret = copy_to_user(to + l, fifo->buffer, len);
- if (unlikely(ret)) {
- *lenout += len - ret;
- return -EFAULT;
- }
- *lenout += len;
- return 0;
-}
-
-unsigned int __kfifo_in_n(struct kfifo *fifo,
- const void *from, unsigned int len, unsigned int recsize)
-{
- if (kfifo_avail(fifo) < len + recsize)
- return len + 1;
-
- __kfifo_in_data(fifo, from, len, recsize);
- return 0;
-}
-EXPORT_SYMBOL(__kfifo_in_n);
-
-/**
- * kfifo_in - puts some data into the FIFO
- * @fifo: the fifo to be used.
- * @from: the data to be added.
- * @len: the length of the data to be added.
- *
- * This function copies at most @len bytes from the @from buffer into
- * the FIFO depending on the free space, and returns the number of
- * bytes copied.
- *
- * Note that with only one concurrent reader and one concurrent
- * writer, you don't need extra locking to use these functions.
- */
-unsigned int kfifo_in(struct kfifo *fifo, const void *from,
- unsigned int len)
-{
- len = min(kfifo_avail(fifo), len);
-
- __kfifo_in_data(fifo, from, len, 0);
- __kfifo_add_in(fifo, len);
- return len;
-}
-EXPORT_SYMBOL(kfifo_in);
-
-unsigned int __kfifo_in_generic(struct kfifo *fifo,
- const void *from, unsigned int len, unsigned int recsize)
-{
- return __kfifo_in_rec(fifo, from, len, recsize);
-}
-EXPORT_SYMBOL(__kfifo_in_generic);
-
-unsigned int __kfifo_out_n(struct kfifo *fifo,
- void *to, unsigned int len, unsigned int recsize)
-{
- if (kfifo_len(fifo) < len + recsize)
- return len;
-
- __kfifo_out_data(fifo, to, len, recsize);
- __kfifo_add_out(fifo, len + recsize);
- return 0;
-}
-EXPORT_SYMBOL(__kfifo_out_n);
-
-/**
- * kfifo_out - gets some data from the FIFO
- * @fifo: the fifo to be used.
- * @to: where the data must be copied.
- * @len: the size of the destination buffer.
- *
- * This function copies at most @len bytes from the FIFO into the
- * @to buffer and returns the number of copied bytes.
- *
- * Note that with only one concurrent reader and one concurrent
- * writer, you don't need extra locking to use these functions.
- */
-unsigned int kfifo_out(struct kfifo *fifo, void *to, unsigned int len)
-{
- len = min(kfifo_len(fifo), len);
-
- __kfifo_out_data(fifo, to, len, 0);
- __kfifo_add_out(fifo, len);
-
- return len;
-}
-EXPORT_SYMBOL(kfifo_out);
-
-/**
- * kfifo_out_peek - copy some data from the FIFO, but do not remove it
- * @fifo: the fifo to be used.
- * @to: where the data must be copied.
- * @len: the size of the destination buffer.
- * @offset: offset into the fifo
- *
- * This function copies at most @len bytes at @offset from the FIFO
- * into the @to buffer and returns the number of copied bytes.
- * The data is not removed from the FIFO.
- */
-unsigned int kfifo_out_peek(struct kfifo *fifo, void *to, unsigned int len,
- unsigned offset)
-{
- len = min(kfifo_len(fifo), len + offset);
-
- __kfifo_out_data(fifo, to, len, offset);
- return len;
-}
-EXPORT_SYMBOL(kfifo_out_peek);
-
-unsigned int __kfifo_out_generic(struct kfifo *fifo,
- void *to, unsigned int len, unsigned int recsize,
- unsigned int *total)
-{
- return __kfifo_out_rec(fifo, to, len, recsize, total);
-}
-EXPORT_SYMBOL(__kfifo_out_generic);
-
-unsigned int __kfifo_from_user_n(struct kfifo *fifo,
- const void __user *from, unsigned int len, unsigned int recsize)
-{
- unsigned total;
-
- if (kfifo_avail(fifo) < len + recsize)
- return len + 1;
-
- __kfifo_from_user_data(fifo, from, len, recsize, &total);
- return total;
-}
-EXPORT_SYMBOL(__kfifo_from_user_n);
-
-/**
- * kfifo_from_user - puts some data from user space into the FIFO
- * @fifo: the fifo to be used.
- * @from: pointer to the data to be added.
- * @len: the length of the data to be added.
- *
- * This function copies at most @len bytes from the @from into the
- * FIFO depending and returns -EFAULT/0.
- *
- * Note that with only one concurrent reader and one concurrent
- * writer, you don't need extra locking to use these functions.
- */
-int kfifo_from_user(struct kfifo *fifo,
- const void __user *from, unsigned int len, unsigned *total)
-{
- int ret;
- len = min(kfifo_avail(fifo), len);
- ret = __kfifo_from_user_data(fifo, from, len, 0, total);
- if (ret)
- return ret;
- __kfifo_add_in(fifo, len);
- return 0;
-}
-EXPORT_SYMBOL(kfifo_from_user);
-
-unsigned int __kfifo_from_user_generic(struct kfifo *fifo,
- const void __user *from, unsigned int len, unsigned int recsize)
-{
- return __kfifo_from_user_rec(fifo, from, len, recsize);
-}
-EXPORT_SYMBOL(__kfifo_from_user_generic);
-
-unsigned int __kfifo_to_user_n(struct kfifo *fifo,
- void __user *to, unsigned int len, unsigned int reclen,
- unsigned int recsize)
-{
- unsigned int ret, total;
-
- if (kfifo_len(fifo) < reclen + recsize)
- return len;
-
- ret = __kfifo_to_user_data(fifo, to, reclen, recsize, &total);
-
- if (likely(ret == 0))
- __kfifo_add_out(fifo, reclen + recsize);
-
- return total;
-}
-EXPORT_SYMBOL(__kfifo_to_user_n);
-
-/**
- * kfifo_to_user - gets data from the FIFO and write it to user space
- * @fifo: the fifo to be used.
- * @to: where the data must be copied.
- * @len: the size of the destination buffer.
- @ @lenout: pointer to output variable with copied data
- *
- * This function copies at most @len bytes from the FIFO into the
- * @to buffer and 0 or -EFAULT.
- *
- * Note that with only one concurrent reader and one concurrent
- * writer, you don't need extra locking to use these functions.
- */
-int kfifo_to_user(struct kfifo *fifo,
- void __user *to, unsigned int len, unsigned *lenout)
-{
- int ret;
- len = min(kfifo_len(fifo), len);
- ret = __kfifo_to_user_data(fifo, to, len, 0, lenout);
- __kfifo_add_out(fifo, *lenout);
- return ret;
-}
-EXPORT_SYMBOL(kfifo_to_user);
-
-unsigned int __kfifo_to_user_generic(struct kfifo *fifo,
- void __user *to, unsigned int len, unsigned int recsize,
- unsigned int *total)
-{
- return __kfifo_to_user_rec(fifo, to, len, recsize, total);
-}
-EXPORT_SYMBOL(__kfifo_to_user_generic);
-
-unsigned int __kfifo_peek_generic(struct kfifo *fifo, unsigned int recsize)
-{
- if (recsize == 0)
- return kfifo_avail(fifo);
-
- return __kfifo_peek_n(fifo, recsize);
-}
-EXPORT_SYMBOL(__kfifo_peek_generic);
-
-void __kfifo_skip_generic(struct kfifo *fifo, unsigned int recsize)
-{
- __kfifo_skip_rec(fifo, recsize);
-}
-EXPORT_SYMBOL(__kfifo_skip_generic);
-
diff -u -N -r -p linux-2.6.33-rc5.dummy/drivers/char/nozomi.c linux-2.6.33-rc5.new/drivers/char/nozomi.c
--- linux-2.6.33-rc5.dummy/drivers/char/nozomi.c 2010-01-27 12:48:09.707017654 +0100
+++ linux-2.6.33-rc5.new/drivers/char/nozomi.c 2010-01-27 13:32:10.042162602 +0100
@@ -1743,7 +1743,7 @@ static int ntty_write_room(struct tty_st
if (!port->port.count)
goto exit;

- room = port->fifo_ul.size - kfifo_len(&port->fifo_ul);
+ room = kfifo_avail(&port->fifo_ul);

exit:
mutex_unlock(&port->tty_sem);
diff -u -N -r -p linux-2.6.33-rc5.dummy/include/linux/kfifo.h linux-2.6.33-rc5.new/include/linux/kfifo.h
--- linux-2.6.33-rc5.dummy/include/linux/kfifo.h 1970-01-01 01:00:00.000000000 +0100
+++ linux-2.6.33-rc5.new/include/linux/kfifo.h 2010-01-27 13:34:06.324991898 +0100
@@ -0,0 +1,812 @@
+/*
+ * A generic kernel FIFO implementation
+ *
+ * Copyright (C) 2009/2010 Stefani Seibold <[email protected]>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ */
+
+#ifndef _LINUX_KFIFO_H
+#define _LINUX_KFIFO_H
+
+/*
+ * How to porting drivers to the new generic FIFO API:
+ *
+ * - Modify the declaration of the "struct kfifo *" object into a
+ * in-place "struct kfifo" object
+ * - Init the in-place object with kfifo_alloc() or kfifo_init()
+ * Note: The address of the in-place "struct kfifo" object must be
+ * passed as the first argument to this functions
+ * - Replace the use of __kfifo_put into kfifo_in and __kfifo_get
+ * into kfifo_out
+ * - Replace the use of kfifo_put into kfifo_in_locked and kfifo_get
+ * into kfifo_out_locked
+ * Note: the spinlock pointer formerly passed to kfifo_init/kfifo_alloc
+ * must be passed now to the kfifo_in_locked and kfifo_out_locked
+ * as the last parameter.
+ * - The formerly __kfifo_* functions are renamed into kfifo_*
+ */
+
+/*
+ * Note about locking : There is no locking required until only * one reader
+ * and one writer is using the fifo and no kfifo_reset() will be * called.
+ * kfifo_reset_out() can be safely used, until it will be only called
+ * in the reader thread.
+ * For multiple writer and one reader there is only a need to lock the writer.
+ * And vice versa for only one writer and multiple reader there is only a need
+ * to lock the reader.
+ */
+
+#include <linux/kernel.h>
+#include <linux/spinlock.h>
+#include <linux/stddef.h>
+#include <linux/scatterlist.h>
+
+struct __kfifo {
+ unsigned int in;
+ unsigned int out;
+ unsigned int mask;
+ unsigned int esize;
+ void *data;
+};
+
+#define __STRUCT_KFIFO_COMMON(datatype, recsize, ptrtype) \
+ union { \
+ struct __kfifo kfifo; \
+ datatype *type; \
+ char (*rectype)[recsize]; \
+ ptrtype *ptr; \
+ const ptrtype *ptr_const; \
+ }
+
+#define __STRUCT_KFIFO(type, size, recsize, ptrtype) \
+{ \
+ __STRUCT_KFIFO_COMMON(type, recsize, ptrtype); \
+ type buf[((size < 2) || (size & (size - 1))) ? -1 : size]; \
+}
+
+#define STRUCT_KFIFO(type, size) \
+ struct __STRUCT_KFIFO(type, size, 0, type)
+
+#define __STRUCT_KFIFO_PTR(type, recsize, ptrtype) \
+{ \
+ __STRUCT_KFIFO_COMMON(type, recsize, ptrtype); \
+ type buf[0]; \
+}
+
+#define STRUCT_KFIFO_PTR(type) \
+ struct __STRUCT_KFIFO_PTR(type, 0, type)
+
+/*
+ * define compatibility "struct kfifo" for dynamic allocated fifos
+ */
+struct kfifo __STRUCT_KFIFO_PTR(unsigned char, 0, void);
+
+#define STRUCT_KFIFO_REC_1(size) \
+ struct __STRUCT_KFIFO(unsigned char, size, 1, void)
+
+#define STRUCT_KFIFO_REC_2(size) \
+ struct __STRUCT_KFIFO(unsigned char, size, 2, void)
+
+/*
+ * define kfifo_rec types
+ */
+struct kfifo_rec_ptr_1 __STRUCT_KFIFO_PTR(unsigned char, 1, void);
+struct kfifo_rec_ptr_2 __STRUCT_KFIFO_PTR(unsigned char, 2, void);
+
+/*
+ * DECLARE_KFIFO_PTR - macro to declare a fifo pointer object
+ * @fifo: name of the declared fifo
+ * @type: type of the fifo elements
+ * @size: the number of elements in the fifo, this must be a power of 2.
+ */
+#define DECLARE_KFIFO_PTR(fifo, type) STRUCT_KFIFO_PTR(type) fifo
+
+/* helper macro */
+#define __is_kfifo_ptr(fifo) (sizeof(*fifo) == sizeof(struct __kfifo))
+
+#define __kfifo_initializer(fifo) \
+ (typeof(fifo)) { \
+ { \
+ { \
+ .in = 0, \
+ .out = 0, \
+ .mask = __is_kfifo_ptr(&fifo) ? \
+ 0 : \
+ sizeof((fifo).buf)/sizeof(*(fifo).buf) - 1, \
+ .esize = sizeof(*(fifo).buf), \
+ .data = __is_kfifo_ptr(&fifo) ? \
+ NULL : \
+ (fifo).buf, \
+ } \
+ } \
+ }
+
+/*
+ * INIT_KFIFO - Initialize a fifo declared by DECLARE_KFIFO
+ * @fifo: name of the declared fifo datatype
+ */
+#define INIT_KFIFO(fifo) fifo = __kfifo_initializer(fifo)
+
+/*
+ * DECLARE_KFIFO - macro to declare a fifo object
+ * @fifo: name of the declared fifo
+ * @type: type of the fifo elements
+ * @size: the number of elements in the fifo, this must be a power of 2.
+ */
+#define DECLARE_KFIFO(fifo, type, size) STRUCT_KFIFO(type, size) fifo
+
+/*
+ * DEFINE_KFIFO - macro to define and initialize a fifo
+ * @fifo: name of the declared fifo datatype
+ * @type: type of the fifo elements
+ * @size: the number of elements in the fifo, this must be a power of 2.
+ *
+ * Note: the macro can be used for global and local fifo data type variables
+ */
+#define DEFINE_KFIFO(fifo, type, size) \
+ DECLARE_KFIFO(fifo, type, size) = __kfifo_initializer(fifo)
+
+static inline unsigned int __must_check __kfifo_check(unsigned int val)
+{
+ return val;
+}
+
+/*
+ * kfifo_initialized - Check if kfifo is initialized.
+ * @fifo: fifo to check
+ * Return %true if FIFO is initialized, otherwise %false.
+ * Assumes the fifo was 0 before.
+ *
+ * Note: for in place fifo's this macro returns alway true
+ */
+#define kfifo_initialized(fifo) ((fifo)->kfifo.data != NULL)
+
+/*
+ * kfifo_esize - returns the size of the element managed by the fifo
+ * @fifo: the fifo to be used.
+ */
+#define kfifo_esize(fifo) ((fifo)->kfifo.esize)
+
+/*
+ * kfifo_recsize - returns the size of the record length field
+ * @fifo: the fifo to be used.
+ */
+#define kfifo_recsize(fifo) (sizeof(*(fifo)->rectype))
+
+/*
+ * kfifo_size - returns the size of the fifo in elements
+ * @fifo: the fifo to be used.
+ */
+#define kfifo_size(fifo) ((fifo)->kfifo.mask + 1)
+
+/*
+ * kfifo_reset - removes the entire fifo content
+ * @fifo: the fifo to be used.
+ *
+ * Note: usage of kfifo_reset() is dangerous. It should be only called when the
+ * fifo is exclusived locked or when it is secured that no other thread is
+ * accessing the fifo.
+ */
+#define kfifo_reset(fifo) \
+(void)({ \
+ typeof(fifo + 1) __tmp = (fifo); \
+ __tmp->kfifo.in = __tmp->kfifo.out = 0; \
+})
+
+/*
+ * kfifo_reset_out - skip fifo content
+ * @fifo: the fifo to be used.
+ *
+ * Note: The usage of kfifo_reset_out() is safe until it will be only called
+ * from the reader thread and there is only one concurrent reader. Otherwise
+ * it is dangerous and must be handled in the same way as kfifo_reset().
+ */
+#define kfifo_reset_out(fifo) \
+(void)({ \
+ typeof(fifo + 1) __tmp = (fifo); \
+ __tmp->kfifo.out = __tmp->kfifo.in; \
+})
+
+/*
+ * kfifo_len - returns the number of used elements in the fifo
+ * @fifo: the fifo to be used.
+ */
+#define kfifo_len(fifo) \
+({ \
+ typeof(fifo + 1) __tmpl = (fifo); \
+ __tmpl->kfifo.in - __tmpl->kfifo.out; \
+})
+
+/*
+ * kfifo_is_empty - returns true if the fifo is empty
+ * @fifo: the fifo to be used.
+ */
+#define kfifo_is_empty(fifo) \
+({ \
+ typeof(fifo + 1) __tmpq = (fifo); \
+ __tmpq->kfifo.in == __tmpq->kfifo.out; \
+})
+
+/*
+ * kfifo_is_full - returns true if the fifo is full
+ * @fifo: the fifo to be used.
+ */
+#define kfifo_is_full(fifo) \
+({ \
+ typeof(fifo + 1) __tmpq = (fifo); \
+ kfifo_len(__tmpq) > __tmpq->kfifo.mask; \
+})
+
+/*
+ * kfifo_avail - returns the number of unused elements in the fifo
+ * @fifo: the fifo to be used.
+ */
+#define kfifo_avail(fifo) \
+__kfifo_check( \
+({ \
+ typeof(fifo + 1) __tmpq = (fifo); \
+ const size_t __recsize = sizeof(*__tmpq->rectype); \
+ unsigned int __avail = kfifo_size(__tmpq) - kfifo_len(__tmpq); \
+ (__recsize) ? ((__avail <= __recsize) ? 0 : \
+ __kfifo_max_r(__avail - __recsize, __recsize)) : \
+ __avail; \
+}) \
+)
+
+/*
+ * kfifo_skip - skip output data
+ * @fifo: the fifo to be used.
+ */
+#define kfifo_skip(fifo) \
+(void)({ \
+ typeof(fifo + 1) __tmp = (fifo); \
+ const size_t __recsize = sizeof(*__tmp->rectype); \
+ struct __kfifo *__kfifo = &__tmp->kfifo; \
+ if (__recsize) \
+ __kfifo_skip_r(__kfifo, __recsize); \
+ else \
+ __kfifo->out++; \
+})
+
+/*
+ * kfifo_peek_len - gets the size of the next FIFO record
+ * @fifo: the fifo to be used.
+ * @recsize: size of record field
+ *
+ * This function returns the size of the next FIFO record in number of bytes
+ */
+#define kfifo_peek_len(fifo) \
+__kfifo_check( \
+({ \
+ typeof(fifo + 1) __tmp = (fifo); \
+ const size_t __recsize = sizeof(*__tmp->rectype); \
+ struct __kfifo *__kfifo = &__tmp->kfifo; \
+ (!__recsize) ? kfifo_len(__tmp) * sizeof(*__tmp->type) : \
+ __kfifo_len_r(__kfifo, __recsize); \
+}) \
+)
+
+/*
+ * kfifo_alloc - dynamically allocates a new fifo
+ * @fifo: pointer to the fifo
+ * @size: the number of elements in the fifo, this must be a power of 2.
+ * @gfp_mask: get_free_pages mask, passed to kmalloc()
+ *
+ * This macro dynamically allocates a new fifo.
+ *
+ * The numer of elements will be rounded-up to a power of 2.
+ * The fifo will be release with kfifo_free().
+ * Return 0 if no error, otherwise an error code
+ */
+#define kfifo_alloc(fifo, size, gfp_mask) \
+__kfifo_check( \
+({ \
+ typeof(fifo + 1) __tmp = (fifo); \
+ struct __kfifo *__kfifo = &__tmp->kfifo; \
+ __is_kfifo_ptr(__tmp) ? \
+ __kfifo_alloc(__kfifo, size, sizeof(*__tmp->type), gfp_mask) : \
+ -EINVAL; \
+}) \
+)
+
+/*
+ * kfifo_free - frees the fifo
+ * @fifo: the fifo to be freed.
+ */
+#define kfifo_free(fifo) \
+({ \
+ typeof(fifo + 1) __tmp = (fifo); \
+ struct __kfifo *__kfifo = &__tmp->kfifo; \
+ if (__is_kfifo_ptr(__tmp)) \
+ __kfifo_free(__kfifo); \
+})
+
+/*
+ * kfifo_init - initialize a FIFO using a preallocated buffer
+ * @fifo: the fifo to assign the buffer
+ * @buffer: the preallocated buffer to be used.
+ * @size: the size of the internal buffer, this have to be a power of 2.
+ */
+#define kfifo_init(fifo, buffer, size) \
+({ \
+ typeof(fifo + 1) __tmp = (fifo); \
+ struct __kfifo *__kfifo = &__tmp->kfifo; \
+ __is_kfifo_ptr(__tmp) ? \
+ __kfifo_init(__kfifo, buffer, size, sizeof(*__tmp->type)) : \
+ -EINVAL; \
+})
+
+/*
+ * kfifo_put - put data into the fifo
+ * @fifo: the fifo to be used.
+ * @val: the data to be added.
+ *
+ * This macro copies the given value into the fifo.
+ *
+ * Note that with only one concurrent reader and one concurrent
+ * writer, you don't need extra locking to use these macro.
+ */
+#define kfifo_put(fifo, val) \
+({ \
+ typeof(fifo + 1) __tmp = (fifo); \
+ typeof(val + 1) __val = (val); \
+ unsigned int __ret; \
+ const size_t __recsize = sizeof(*__tmp->rectype); \
+ struct __kfifo *__kfifo = &__tmp->kfifo; \
+ if (0) { \
+ typeof(__tmp->ptr_const) __dummy __attribute__ ((unused)); \
+ __dummy = (typeof(__val))NULL; \
+ } \
+ if (__recsize) \
+ __ret = __kfifo_in_r(__kfifo, __val, sizeof(*__val), \
+ __recsize); \
+ else { \
+ __ret = !kfifo_is_full(__tmp); \
+ if (__ret) { \
+ (__is_kfifo_ptr(__tmp) ? \
+ ((typeof(__tmp->type))__kfifo->data) : \
+ (__tmp->buf) \
+ )[__kfifo->in & __tmp->kfifo.mask] = \
+ *(typeof(__tmp->type))__val; \
+ smp_wmb(); \
+ __kfifo->in++; \
+ } \
+ } \
+ __ret; \
+})
+
+/*
+ * kfifo_get - get data from the fifo
+ * @fifo: the fifo to be used.
+ * @val: the var where to store the data to be added.
+ *
+ * This macro returns the data from the fifo
+ *
+ * Note that with only one concurrent reader and one concurrent
+ * writer, you don't need extra locking to use these macro.
+ */
+#define kfifo_get(fifo, val) \
+({ \
+ typeof(fifo + 1) __tmp = (fifo); \
+ typeof(val + 1) __val = (val); \
+ unsigned int __ret; \
+ const size_t __recsize = sizeof(*__tmp->rectype); \
+ struct __kfifo *__kfifo = &__tmp->kfifo; \
+ if (0) \
+ __val = (typeof(__tmp->ptr))0; \
+ if (__recsize) \
+ __ret = __kfifo_out_r(__kfifo, __val, sizeof(*__val), \
+ __recsize); \
+ else { \
+ __ret = !kfifo_is_empty(__tmp); \
+ if (__ret) { \
+ *(typeof(__tmp->type))__val = \
+ (__is_kfifo_ptr(__tmp) ? \
+ ((typeof(__tmp->type))__kfifo->data) : \
+ (__tmp->buf) \
+ )[__kfifo->out & __tmp->kfifo.mask]; \
+ smp_wmb(); \
+ __kfifo->out++; \
+ } \
+ } \
+ __ret; \
+})
+
+/*
+ * kfifo_peek - get data from the fifo without removing
+ * @fifo: the fifo to be used.
+ * @val: the var where to store the data to be added.
+ *
+ * This macro returns the data from the fifo without removing it from the fifo
+ *
+ * Note that with only one concurrent reader and one concurrent
+ * writer, you don't need extra locking to use these macro.
+ */
+#define kfifo_peek(fifo, val) \
+({ \
+ typeof(fifo + 1) __tmp = (fifo); \
+ typeof(val + 1) __val = (val); \
+ unsigned int __ret; \
+ const size_t __recsize = sizeof(*__tmp->rectype); \
+ struct __kfifo *__kfifo = &__tmp->kfifo; \
+ if (0) \
+ __val = (typeof(__tmp->ptr))NULL; \
+ if (__recsize) \
+ __ret = __kfifo_out_peek_r(__kfifo, __val, sizeof(*__val), \
+ __recsize); \
+ else { \
+ __ret = !kfifo_is_empty(__tmp); \
+ if (__ret) { \
+ *(typeof(__tmp->type))__val = \
+ (__is_kfifo_ptr(__tmp) ? \
+ ((typeof(__tmp->type))__kfifo->data) : \
+ (__tmp->buf) \
+ )[__kfifo->out & __tmp->kfifo.mask]; \
+ smp_wmb(); \
+ } \
+ } \
+ __ret; \
+})
+
+/*
+ * kfifo_in - puts some data into the fifo
+ * @fifo: the fifo to be used.
+ * @buf: the data to be added.
+ * @n: number of elements to be added
+ *
+ * This macro copies the given values buffer into the fifo and returns the
+ * number of copied elements.
+ *
+ * Note that with only one concurrent reader and one concurrent
+ * writer, you don't need extra locking to use these macro.
+ */
+#define kfifo_in(fifo, buf, n) \
+({ \
+ typeof(fifo + 1) __tmp = (fifo); \
+ typeof(buf + 1) __buf = (buf); \
+ unsigned long __n = (n); \
+ const size_t __recsize = sizeof(*__tmp->rectype); \
+ struct __kfifo *__kfifo = &__tmp->kfifo; \
+ if (0) { \
+ typeof(__tmp->ptr_const) __dummy __attribute__ ((unused)); \
+ __dummy = (typeof(__buf))NULL; \
+ } \
+ (__recsize) ?\
+ __kfifo_in_r(__kfifo, __buf, __n, __recsize) : \
+ __kfifo_in(__kfifo, __buf, __n); \
+})
+
+/*
+ * kfifo_in_locked - puts some data into the fifo using a spinlock for locking
+ * @fifo: the fifo to be used.
+ * @buf: the data to be added.
+ * @n: number of elements to be added
+ * @lock: pointer to the spinlock to use for locking.
+ *
+ * This macro copies the given values buffer into the fifo and returns the
+ * number of copied elements.
+ */
+#define kfifo_in_locked(fifo, buf, n, lock) \
+({ \
+ unsigned long __flags; \
+ unsigned int __ret; \
+ spin_lock_irqsave(lock, __flags); \
+ __ret = kfifo_in(fifo, buf, n); \
+ spin_unlock_irqrestore(lock, __flags); \
+ __ret; \
+})
+
+/*
+ * kfifo_out - gets some data from the fifo
+ * @fifo: the fifo to be used.
+ * @buf: pointer to the storage buffer
+ * @n: max. number of elements to get
+ *
+ * This macro get the data from the fifo and return the numbers of elements
+ * copied.
+ *
+ * Note that with only one concurrent reader and one concurrent
+ * writer, you don't need extra locking to use these macro.
+ */
+#define kfifo_out(fifo, buf, n) \
+__kfifo_check( \
+({ \
+ typeof(fifo + 1) __tmp = (fifo); \
+ typeof(buf + 1) __buf = (buf); \
+ unsigned long __n = (n); \
+ const size_t __recsize = sizeof(*__tmp->rectype); \
+ struct __kfifo *__kfifo = &__tmp->kfifo; \
+ if (0) { \
+ typeof(__tmp->ptr) __dummy = NULL; \
+ __buf = __dummy; \
+ } \
+ (__recsize) ?\
+ __kfifo_out_r(__kfifo, __buf, __n, __recsize) : \
+ __kfifo_out(__kfifo, __buf, __n); \
+}) \
+)
+
+/*
+ * kfifo_out_locked - gets some data from the fifo using a spinlock for locking
+ * @fifo: the fifo to be used.
+ * @buf: pointer to the storage buffer
+ * @n: max. number of elements to get
+ * @lock: pointer to the spinlock to use for locking.
+ *
+ * This macro get the data from the fifo and return the numbers of elements
+ * copied.
+ */
+#define kfifo_out_locked(fifo, buf, n, lock) \
+__kfifo_check( \
+({ \
+ unsigned long __flags; \
+ unsigned int __ret; \
+ spin_lock_irqsave(lock, __flags); \
+ __ret = kfifo_out(fifo, buf, n); \
+ spin_unlock_irqrestore(lock, __flags); \
+ __ret; \
+}) \
+)
+
+/*
+ * kfifo_from_user - puts some data from user space into the fifo
+ * @fifo: the fifo to be used.
+ * @from: pointer to the data to be added.
+ * @len: the length of the data to be added.
+ * @copied: pointer to output variable to store the number of copied bytes.
+ *
+ * This macro copies at most @len bytes from the @from into the
+ * fifo, depending of the available space and returns -EFAULT/0
+ *
+ * Note that with only one concurrent reader and one concurrent
+ * writer, you don't need extra locking to use these macro.
+ */
+#define kfifo_from_user(fifo, from, len, copied) \
+__kfifo_check( \
+({ \
+ typeof(fifo + 1) __tmp = (fifo); \
+ const void __user *__from = (from); \
+ unsigned int __len = (len); \
+ unsigned int *__copied = (copied); \
+ const size_t __recsize = sizeof(*__tmp->rectype); \
+ struct __kfifo *__kfifo = &__tmp->kfifo; \
+ (__recsize) ? \
+ __kfifo_from_user_r(__kfifo, __from, __len, __copied, __recsize) : \
+ __kfifo_from_user(__kfifo, __from, __len, __copied); \
+}) \
+)
+
+/*
+ * kfifo_to_user - copies data from the fifo into user space
+ * @fifo: the fifo to be used.
+ * @to: where the data must be copied.
+ * @len: the size of the destination buffer.
+ * @copied: pointer to output variable to store the number of copied bytes.
+ *
+ * This macro copies at most @len bytes from the fifo into the
+ * @to buffer and returns -EFAULT/0.
+ *
+ * Note that with only one concurrent reader and one concurrent
+ * writer, you don't need extra locking to use these macro.
+ */
+#define kfifo_to_user(fifo, to, len, copied) \
+__kfifo_check( \
+({ \
+ typeof(fifo + 1) __tmp = (fifo); \
+ void __user *__to = (to); \
+ unsigned int __len = (len); \
+ unsigned int *__copied = (copied); \
+ const size_t __recsize = sizeof(*__tmp->rectype); \
+ struct __kfifo *__kfifo = &__tmp->kfifo; \
+ (__recsize) ? \
+ __kfifo_to_user_r(__kfifo, __to, __len, __copied, __recsize) : \
+ __kfifo_to_user(__kfifo, __to, __len, __copied); \
+}) \
+)
+
+/*
+ * kfifo_dma_in_prepare - setup a scatterlist for DMA input
+ * @fifo: the fifo to be used.
+ * @sgl: pointer to the scatterlist array.
+ * @nents: number of entries in the scatterlist array
+ * @len: number of elements to transfer.
+ *
+ * This macro fills a scatterlist for DMA input.
+ * It returns the number entries in the scatterlist array
+ *
+ * Note that with only one concurrent reader and one concurrent
+ * writer, you don't need extra locking to use these macros.
+ */
+#define kfifo_dma_in_prepare(fifo, sgl, nents, len) \
+({ \
+ typeof(fifo + 1) __tmp = (fifo); \
+ struct scatterlist *__sgl = (sgl); \
+ int __nents = (nents); \
+ unsigned int __len = (len); \
+ const size_t __recsize = sizeof(*__tmp->rectype); \
+ struct __kfifo *__kfifo = &__tmp->kfifo; \
+ (__recsize) ? \
+ __kfifo_dma_in_prepare_r(__kfifo, __sgl, __nents, __len, __recsize) : \
+ __kfifo_dma_in_prepare(__kfifo,__sgl, __nents, __len); \
+})
+
+/*
+ * kfifo_dma_in_finish - finish a DMA IN operation
+ * @fifo: the fifo to be used.
+ * @len: number of bytes to received.
+ *
+ * This macro finish a DMA IN operation. The in counter will be updated by
+ * the len parameter. No error checking will be done.
+ *
+ * Note that with only one concurrent reader and one concurrent
+ * writer, you don't need extra locking to use these macros.
+ */
+#define kfifo_dma_in_finish(fifo, len) \
+(void)({ \
+ typeof(fifo + 1) __tmp = (fifo); \
+ unsigned int __len = (len); \
+ const size_t __recsize = sizeof(*__tmp->rectype); \
+ struct __kfifo *__kfifo = &__tmp->kfifo; \
+ if (__recsize) \
+ __kfifo_dma_in_finish_r(__kfifo, __len, __recsize); \
+ else \
+ __kfifo->in += __len / sizeof(*__tmp->type); \
+})
+
+/*
+ * kfifo_dma_out_prepare - setup a scatterlist for DMA output
+ * @fifo: the fifo to be used.
+ * @sgl: pointer to the scatterlist array.
+ * @nents: number of entries in the scatterlist array
+ * @len: number of elements to transfer.
+ *
+ * This macro fills a scatterlist for DMA output which at most @len bytes
+ * to transfer.
+ * It returns the number entries in the scatterlist array
+ * A zero means there is no space available and the scatterlist is not filled
+ *
+ * Note that with only one concurrent reader and one concurrent
+ * writer, you don't need extra locking to use these macros.
+ */
+#define kfifo_dma_out_prepare(fifo, sgl, nents, len) \
+({ \
+ typeof(fifo + 1) __tmp = (fifo); \
+ struct scatterlist *__sgl = (sgl); \
+ int __nents = (nents); \
+ unsigned int __len = (len); \
+ const size_t __recsize = sizeof(*__tmp->rectype); \
+ struct __kfifo *__kfifo = &__tmp->kfifo; \
+ (__recsize) ? \
+ __kfifo_dma_out_prepare_r(__kfifo, __sgl, __nents, __len, __recsize) : \
+ __kfifo_dma_out_prepare(__kfifo, __sgl, __nents, __len); \
+})
+
+/*
+ * kfifo_dma_out_finish - finish a DMA OUT operation
+ * @fifo: the fifo to be used.
+ * @len: number of bytes transferd.
+ *
+ * This macro finish a DMA OUT operation. The out counter will be updated by
+ * the len parameter. No error checking will be done.
+ *
+ * Note that with only one concurrent reader and one concurrent
+ * writer, you don't need extra locking to use these macros.
+ */
+#define kfifo_dma_out_finish(fifo, len) \
+(void)({ \
+ typeof(fifo + 1) __tmp = (fifo); \
+ unsigned int __len = (len); \
+ const size_t __recsize = sizeof(*__tmp->rectype); \
+ struct __kfifo *__kfifo = &__tmp->kfifo; \
+ if (__recsize) \
+ __kfifo_dma_out_finish_r(__kfifo, __recsize); \
+ else \
+ __kfifo->out += __len / sizeof(*__tmp->type); \
+})
+
+/*
+ * kfifo_out_peek - gets some data from the fifo
+ * @fifo: the fifo to be used.
+ * @buf: pointer to the storage buffer
+ * @n: max. number of elements to get
+ *
+ * This macro get the data from the fifo and return the numbers of elements
+ * copied. The data is not removed from the FIFO.
+ *
+ * Note that with only one concurrent reader and one concurrent
+ * writer, you don't need extra locking to use these macro.
+ */
+#define kfifo_out_peek(fifo, buf, n) \
+__kfifo_check( \
+({ \
+ typeof(fifo + 1) __tmp = (fifo); \
+ typeof(buf + 1) __buf = (buf); \
+ unsigned long __n = (n); \
+ const size_t __recsize = sizeof(*__tmp->rectype); \
+ struct __kfifo *__kfifo = &__tmp->kfifo; \
+ if (0) { \
+ typeof(__tmp->ptr) __dummy __attribute__ ((unused)) = NULL; \
+ __buf = __dummy; \
+ } \
+ (__recsize) ? \
+ __kfifo_out_peek_r(__kfifo, __buf, __n, __recsize) : \
+ __kfifo_out_peek(__kfifo, __buf, __n); \
+}) \
+)
+
+extern int __kfifo_alloc(struct __kfifo *fifo, unsigned int size,
+ size_t esize, gfp_t gfp_mask);
+
+extern void __kfifo_free(struct __kfifo *fifo);
+
+extern int __kfifo_init(struct __kfifo *fifo, void *buffer,
+ unsigned int size, size_t esize);
+
+extern unsigned int __kfifo_in(struct __kfifo *fifo,
+ const void *buf, unsigned int len);
+
+extern unsigned int __kfifo_out(struct __kfifo *fifo,
+ void *buf, unsigned int len);
+
+extern int __kfifo_from_user(struct __kfifo *fifo,
+ const void __user *from, unsigned long len, unsigned int *copied);
+
+extern int __kfifo_to_user(struct __kfifo *fifo,
+ void __user *to, unsigned long len, unsigned int *copied);
+
+extern unsigned int __kfifo_dma_in_prepare(struct __kfifo *fifo,
+ struct scatterlist *sgl, int nents, unsigned int len);
+
+extern unsigned int __kfifo_dma_out_prepare(struct __kfifo *fifo,
+ struct scatterlist *sgl, int nents, unsigned int len);
+
+extern unsigned int __kfifo_out_peek(struct __kfifo *fifo,
+ void *buf, unsigned int len);
+
+extern unsigned int __kfifo_in_r(struct __kfifo *fifo,
+ const void *buf, unsigned int len, size_t recsize);
+
+extern unsigned int __kfifo_out_r(struct __kfifo *fifo,
+ void *buf, unsigned int len, size_t recsize);
+
+extern int __kfifo_from_user_r(struct __kfifo *fifo,
+ const void __user *from, unsigned long len, unsigned int *copied,
+ size_t recsize);
+
+extern int __kfifo_to_user_r(struct __kfifo *fifo, void __user *to,
+ unsigned long len, unsigned int *copied, size_t recsize);
+
+extern unsigned int __kfifo_dma_in_prepare_r(struct __kfifo *fifo,
+ struct scatterlist *sgl, int nents, unsigned int len, size_t recsize);
+
+extern void __kfifo_dma_in_finish_r(struct __kfifo *fifo,
+ unsigned int len, size_t recsize);
+
+extern unsigned int __kfifo_dma_out_prepare_r(struct __kfifo *fifo,
+ struct scatterlist *sgl, int nents, unsigned int len, size_t recsize);
+
+extern void __kfifo_dma_out_finish_r(struct __kfifo *fifo, size_t recsize);
+
+extern unsigned int __kfifo_len_r(struct __kfifo *fifo, size_t recsize);
+
+extern unsigned int __kfifo_out_peek_r(struct __kfifo *fifo,
+ void *buf, unsigned int len, size_t recsize);
+
+extern unsigned int __kfifo_max_r(unsigned int len, size_t recsize);
+
+#endif
+
diff -u -N -r -p linux-2.6.33-rc5.dummy/kernel/kfifo.c linux-2.6.33-rc5.new/kernel/kfifo.c
--- linux-2.6.33-rc5.dummy/kernel/kfifo.c 1970-01-01 01:00:00.000000000 +0100
+++ linux-2.6.33-rc5.new/kernel/kfifo.c 2010-01-27 13:33:56.456825816 +0100
@@ -0,0 +1,583 @@
+/*
+ * A generic kernel FIFO implementation
+ *
+ * Copyright (C) 2009/2010 Stefani Seibold <[email protected]>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/err.h>
+#include <linux/kfifo.h>
+#include <linux/log2.h>
+#include <linux/uaccess.h>
+
+static unsigned int roundup_diff(unsigned int val, unsigned int size)
+{
+ if (size <= 1)
+ return size;
+ return (val + size - 1) / size;
+}
+
+static inline unsigned int kfifo_unused(struct __kfifo *fifo)
+{
+ return (fifo->mask + 1) - (fifo->in - fifo->out);
+}
+
+int __kfifo_alloc(struct __kfifo *fifo, unsigned int size,
+ size_t esize, gfp_t gfp_mask)
+{
+ /*
+ * round up to the next power of 2, since our 'let the indices
+ * wrap' technique works only in this case.
+ */
+ if (!is_power_of_2(size))
+ size = rounddown_pow_of_two(size);
+
+ if (size < 2)
+ return -EINVAL;
+
+ fifo->in = fifo->out = 0;
+ fifo->data = kmalloc(size * esize, gfp_mask);
+
+ if (!fifo->data) {
+ fifo->mask = 0;
+ return -ENOMEM;
+ }
+
+ fifo->mask = size - 1;
+ fifo->esize = esize;
+
+ return 0;
+}
+EXPORT_SYMBOL(__kfifo_alloc);
+
+void __kfifo_free(struct __kfifo *fifo)
+{
+ kfree(fifo);
+ fifo->data = 0;
+ fifo->mask = 0;
+ fifo->in = fifo->out = 0;
+}
+EXPORT_SYMBOL(__kfifo_free);
+
+int __kfifo_init(struct __kfifo *fifo, void *buffer,
+ unsigned int size, size_t esize)
+{
+ size /= esize;
+
+ if (size)
+ size = rounddown_pow_of_two(size);
+
+ if (size < 2)
+ return -EINVAL;
+
+ fifo->data = buffer;
+ fifo->in = fifo->out = 0;
+ fifo->mask = size - 1;
+ fifo->esize = esize;
+ return 0;
+}
+EXPORT_SYMBOL(__kfifo_init);
+
+static void kfifo_copy_in(struct __kfifo *fifo, const void *src,
+ unsigned int len, unsigned int off)
+{
+ unsigned int size = fifo->mask + 1;
+ unsigned int esize = fifo->esize;
+ unsigned int l;
+
+ off &= fifo->mask;
+ if (esize != 1) {
+ off *= esize;
+ size *= esize;
+ len *= esize;
+ }
+ l = min(len, size - off);
+
+ memcpy(fifo->data + off, src, l);
+ memcpy(fifo->data, src + l, len - l);
+ smp_wmb();
+}
+
+unsigned int __kfifo_in(struct __kfifo *fifo,
+ const void *buf, unsigned int len)
+{
+ unsigned int l;
+
+ l = kfifo_unused(fifo);
+ if (len > l)
+ len = l;
+
+ kfifo_copy_in(fifo, buf, len, fifo->in);
+ fifo->in += len;
+ return len;
+}
+EXPORT_SYMBOL(__kfifo_in);
+
+static void kfifo_copy_out(struct __kfifo *fifo, void *dst,
+ unsigned int len, unsigned int off)
+{
+ unsigned int size = fifo->mask + 1;
+ unsigned int esize = fifo->esize;
+ unsigned int l;
+
+ off &= fifo->mask;
+ if (esize != 1) {
+ off *= esize;
+ size *= esize;
+ len *= esize;
+ }
+ l = min(len, size - off);
+
+ memcpy(dst, fifo->data + off, l);
+ memcpy(dst + l, fifo->data, len - l);
+ smp_wmb();
+}
+
+unsigned int __kfifo_out_peek(struct __kfifo *fifo,
+ void *buf, unsigned int len)
+{
+ unsigned int l;
+
+ l = fifo->in - fifo->out;
+ if (len > l)
+ len = l;
+
+ kfifo_copy_out(fifo, buf, len, fifo->out);
+ return len;
+}
+EXPORT_SYMBOL(__kfifo_out_peek);
+
+unsigned int __kfifo_out(struct __kfifo *fifo,
+ void *buf, unsigned int len)
+{
+ len = __kfifo_out_peek(fifo, buf, len);
+ fifo->out += len;
+ return len;
+}
+EXPORT_SYMBOL(__kfifo_out);
+
+static unsigned long kfifo_copy_from_user(struct __kfifo *fifo,
+ const void *src, unsigned int len, unsigned int off,
+ unsigned int *copied)
+{
+ unsigned int size = fifo->mask + 1;
+ unsigned int esize = fifo->esize;
+ unsigned int l;
+ unsigned long ret;
+
+ off &= fifo->mask;
+ if (esize != 1) {
+ off *= esize;
+ size *= esize;
+ len *= esize;
+ }
+ l = min(len, size - off);
+
+ ret = copy_from_user(fifo->data + off, src, l);
+ if (unlikely(ret))
+ ret = roundup_diff(ret + len - l, esize);
+ else {
+ ret = copy_from_user(fifo->data, src + l, len - l);
+ if (unlikely(ret))
+ ret = roundup_diff(ret, esize);
+ }
+ smp_wmb();
+ if (copied)
+ *copied = len - ret;
+ return ret;
+}
+
+int __kfifo_from_user(struct __kfifo *fifo, const void __user *from,
+ unsigned long len, unsigned int *copied)
+{
+ unsigned int l;
+ unsigned long ret;
+ unsigned int esize = fifo->esize;
+ int err;
+
+ if (esize != 1)
+ len /= esize;
+
+ l = kfifo_unused(fifo);
+ if (len > l)
+ len = l;
+
+ ret = kfifo_copy_from_user(fifo, from, len, fifo->in, copied);
+ if (unlikely(ret)) {
+ len -= ret;
+ err = -EFAULT;
+ }
+ else
+ err = 0;
+ fifo->in += len;
+ return err;
+}
+EXPORT_SYMBOL(__kfifo_from_user);
+
+static unsigned long kfifo_copy_to_user(struct __kfifo *fifo, void *dst,
+ unsigned int len, unsigned int off, unsigned int *copied)
+{
+ unsigned int l;
+ unsigned long ret;
+ unsigned int size = fifo->mask + 1;
+ unsigned int esize = fifo->esize;
+
+ off &= fifo->mask;
+ if (esize != 1) {
+ off *= esize;
+ size *= esize;
+ len *= esize;
+ }
+ l = min(len, size - off);
+
+ ret = copy_to_user(dst, fifo->data + off, l);
+ if (unlikely(ret))
+ ret = roundup_diff(ret + len - l, esize);
+ else {
+ ret = copy_to_user(dst + l, fifo->data, len - l);
+ if (unlikely(ret))
+ ret = roundup_diff(ret, esize);
+ }
+ smp_wmb();
+ if (copied)
+ *copied = len - ret;
+ return ret;
+}
+
+int __kfifo_to_user(struct __kfifo *fifo, void __user *to,
+ unsigned long len, unsigned int *copied)
+{
+ unsigned int l;
+ unsigned long ret;
+ unsigned int esize = fifo->esize;
+ int err;
+
+ if (esize != 1)
+ len /= esize;
+
+ l = fifo->in - fifo->out;
+ if (len > l)
+ len = l;
+ ret = kfifo_copy_to_user(fifo, to, len, fifo->out, copied);
+ if (unlikely(ret)) {
+ len -= ret;
+ err = -EFAULT;
+ }
+ else
+ err = 0;
+ fifo->out += len;
+ return err;
+}
+EXPORT_SYMBOL(__kfifo_to_user);
+
+static int setup_sgl_buf(struct scatterlist *sgl, void *buf,
+ int nents, unsigned int len)
+{
+ int n;
+ unsigned int l;
+ unsigned int off;
+ struct page *page;
+
+ if (!nents)
+ return 0;
+
+ if (!len)
+ return 0;
+
+ n = 0;
+ page = virt_to_page(buf);
+ off = offset_in_page(buf);
+ l = 0;
+
+ while(len >= l + PAGE_SIZE - off) {
+ struct page *npage;
+
+ l += PAGE_SIZE;
+ buf += PAGE_SIZE;
+ npage = virt_to_page(buf);
+ if (page_to_phys(page) != page_to_phys(npage) - l) {
+ sgl->page_link = 0;
+ sg_set_page(sgl++, page, l - off, off);
+ if (++n == nents)
+ return n;
+ page = npage;
+ len -= l - off;
+ l = off = 0;
+ }
+ }
+ sgl->page_link = 0;
+ sg_set_page(sgl++, page, len, off);
+ return n + 1;
+}
+
+static unsigned int setup_sgl(struct __kfifo *fifo, struct scatterlist *sgl,
+ int nents, unsigned int len, unsigned int off)
+{
+ unsigned int size = fifo->mask + 1;
+ unsigned int esize = fifo->esize;
+ unsigned int l;
+ unsigned int n;
+
+ off &= fifo->mask;
+ if (esize != 1) {
+ off *= esize;
+ size *= esize;
+ len *= esize;
+ }
+ l = min(len, size - off);
+
+ n = setup_sgl_buf(sgl, fifo->data + off, nents, l);
+ n += setup_sgl_buf(sgl + n, fifo->data, nents - n, len - l);
+
+ if (n)
+ sg_mark_end(sgl + n - 1);
+ return n;
+}
+
+unsigned int __kfifo_dma_in_prepare(struct __kfifo *fifo,
+ struct scatterlist *sgl, int nents, unsigned int len)
+{
+ unsigned int l;
+
+ l = kfifo_unused(fifo);
+ if (len > l)
+ len = l;
+
+ return setup_sgl(fifo, sgl, nents, len, fifo->in);
+}
+EXPORT_SYMBOL(__kfifo_dma_in_prepare);
+
+unsigned int __kfifo_dma_out_prepare(struct __kfifo *fifo,
+ struct scatterlist *sgl, int nents, unsigned int len)
+{
+ unsigned int l;
+
+ l = fifo->in - fifo->out;
+ if (len > l)
+ len = l;
+
+ return setup_sgl(fifo, sgl, nents, len, fifo->out);
+}
+EXPORT_SYMBOL(__kfifo_dma_out_prepare);
+
+unsigned int __kfifo_max_r(unsigned int len, size_t recsize)
+{
+ unsigned int max = (1 << (recsize << 3)) - 1;
+
+ if (len > max)
+ return max;
+ return len;
+}
+
+#define __KFIFO_PEEK(data, out, mask) \
+ ((data)[(out) & (mask)])
+/**
+ * __kfifo_peek_n internal helper function for determinate the length of
+ * the next record in the fifo
+ */
+static unsigned int __kfifo_peek_n(struct __kfifo *fifo, size_t recsize)
+{
+ unsigned int l;
+ unsigned int mask = fifo->mask;
+ unsigned char *data = fifo->data;
+
+ l = __KFIFO_PEEK(data, fifo->out, mask);
+
+ if (--recsize)
+ l |= __KFIFO_PEEK(data, fifo->out + 1, mask) << 8;
+
+ return l;
+}
+
+#define __KFIFO_POKE(data, in, mask, val) \
+ ( \
+ (data)[(in) & (mask)] = (unsigned char)(val) \
+ )
+
+/**
+ * __kfifo_poke_n internal helper function for storeing the length of
+ * the record into the fifo
+ */
+static void __kfifo_poke_n(struct __kfifo *fifo, unsigned int n, size_t recsize)
+{
+ unsigned int mask = fifo->mask;
+ unsigned char *data = fifo->data;
+
+ __KFIFO_POKE(data, fifo->in, mask, n);
+
+ if (recsize > 1)
+ __KFIFO_POKE(data, fifo->in + 1, mask, n >> 8);
+}
+
+unsigned int __kfifo_len_r(struct __kfifo *fifo, size_t recsize)
+{
+ return __kfifo_peek_n(fifo, recsize);
+}
+EXPORT_SYMBOL(__kfifo_len_r);
+
+unsigned int __kfifo_in_r(struct __kfifo *fifo, const void *buf,
+ unsigned int len, size_t recsize)
+{
+ if (len + recsize > kfifo_unused(fifo))
+ return 0;
+
+ __kfifo_poke_n(fifo, len, recsize);
+
+ kfifo_copy_in(fifo, buf, len, fifo->in + recsize);
+ fifo->in += len + recsize;
+ return len;
+}
+EXPORT_SYMBOL(__kfifo_in_r);
+
+static unsigned int kfifo_out_copy_r(struct __kfifo *fifo,
+ void *buf, unsigned int len, size_t recsize, unsigned int *n)
+{
+ *n = __kfifo_peek_n(fifo, recsize);
+
+ if (len > *n)
+ len = *n;
+
+ kfifo_copy_out(fifo, buf, len, fifo->out + recsize);
+ return len;
+}
+
+unsigned int __kfifo_out_peek_r(struct __kfifo *fifo, void *buf,
+ unsigned int len, size_t recsize)
+{
+ unsigned int n;
+
+ if (fifo->in == fifo->out)
+ return 0;
+
+ return kfifo_out_copy_r(fifo, buf, len, recsize, &n);
+}
+EXPORT_SYMBOL(__kfifo_out_peek_r);
+
+unsigned int __kfifo_out_r(struct __kfifo *fifo, void *buf,
+ unsigned int len, size_t recsize)
+{
+ unsigned int n;
+
+ if (fifo->in == fifo->out)
+ return 0;
+
+ len = kfifo_out_copy_r(fifo, buf, len, recsize, &n);
+ fifo->out += n + recsize;
+ return len;
+}
+EXPORT_SYMBOL(__kfifo_out_r);
+
+int __kfifo_from_user_r(struct __kfifo *fifo, const void __user *from,
+ unsigned long len, unsigned int *copied, size_t recsize)
+{
+ unsigned long ret;
+
+ len = __kfifo_max_r(len, recsize);
+
+ if (len + recsize > kfifo_unused(fifo)) {
+ *copied = 0;
+ return 0;
+ }
+
+ __kfifo_poke_n(fifo, len, recsize);
+
+ ret = kfifo_copy_from_user(fifo, from, len, fifo->in + recsize, copied);
+ if (unlikely(ret)) {
+ *copied = 0;
+ return -EFAULT;
+ }
+ fifo->in += len + recsize;
+ return 0;
+}
+EXPORT_SYMBOL(__kfifo_from_user_r);
+
+int __kfifo_to_user_r(struct __kfifo *fifo, void __user *to,
+ unsigned long len, unsigned int *copied, size_t recsize)
+{
+ unsigned long ret;
+ unsigned int n;
+
+ if (fifo->in == fifo->out) {
+ *copied = 0;
+ return 0;
+ }
+
+ n = __kfifo_peek_n(fifo, recsize);
+ if (len > n)
+ len = n;
+
+ ret = kfifo_copy_to_user(fifo, to, len, fifo->out + recsize, copied);
+ if (unlikely(ret)) {
+ *copied = 0;
+ return -EFAULT;
+ }
+ fifo->out += n + recsize;
+ return 0;
+}
+EXPORT_SYMBOL(__kfifo_to_user_r);
+
+unsigned int __kfifo_dma_in_prepare_r(struct __kfifo *fifo,
+ struct scatterlist *sgl, int nents, unsigned int len, size_t recsize)
+{
+ if (!nents)
+ BUG();
+
+ len = __kfifo_max_r(len, recsize);
+
+ if (len + recsize > kfifo_unused(fifo))
+ return 0;
+
+ return setup_sgl(fifo, sgl, nents, len, fifo->in + recsize);
+}
+EXPORT_SYMBOL(__kfifo_dma_in_prepare_r);
+
+void __kfifo_dma_in_finish_r(struct __kfifo *fifo,
+ unsigned int len, size_t recsize)
+{
+ len = __kfifo_max_r(len, recsize);
+ __kfifo_poke_n(fifo, len, recsize);
+ fifo->in += len + recsize;
+}
+EXPORT_SYMBOL(__kfifo_dma_in_finish_r);
+
+unsigned int __kfifo_dma_out_prepare_r(struct __kfifo *fifo,
+ struct scatterlist *sgl, int nents, unsigned int len, size_t recsize)
+{
+ if (!nents)
+ BUG();
+
+ len = __kfifo_max_r(len, recsize);
+
+ if (len + recsize > fifo->in - fifo->out)
+ return 0;
+
+ return setup_sgl(fifo, sgl, nents, len, fifo->out + recsize);
+}
+EXPORT_SYMBOL(__kfifo_dma_out_prepare_r);
+
+void __kfifo_dma_out_finish_r(struct __kfifo *fifo, size_t recsize)
+{
+ unsigned int len;
+
+ len = __kfifo_peek_n(fifo, recsize);
+ fifo->out += len + recsize;
+}
+EXPORT_SYMBOL(__kfifo_dma_out_finish_r);
+

2010-02-03 20:06:22

by Andrew Morton

Subject: Re: [PATCH] enhanced reimplemention of the kfifo API

On Wed, 27 Jan 2010 14:00:43 +0100
Stefani Seibold <[email protected]> wrote:

> This is a complete reimplementation of the new kfifo API, which is now
> really generic, type save and type definable.
>
>
> ...
>
> diff -u -N -r -p linux-2.6.33-rc5.dummy/include/linux/kfifo.h linux-2.6.33-rc5.new/include/linux/kfifo.h
> --- linux-2.6.33-rc5.dummy/include/linux/kfifo.h 1970-01-01 01:00:00.000000000 +0100
> +++ linux-2.6.33-rc5.new/include/linux/kfifo.h 2010-01-27 13:34:06.324991898 +0100
>
> ...
>
> +/*
> + * DECLARE_KFIFO_PTR - macro to declare a fifo pointer object
> + * @fifo: name of the declared fifo
> + * @type: type of the fifo elements
> + * @size: the number of elements in the fifo, this must be a power of 2.
> + */

Throughout this patch the comments are in kerneldoc form, but they
don't use the /** opening token, so the kerneldoc tools will ignore them.

Please fix that up and test it.

> +#define DECLARE_KFIFO_PTR(fifo, type) STRUCT_KFIFO_PTR(type) fifo
> +
> +/* helper macro */
> +#define __is_kfifo_ptr(fifo) (sizeof(*fifo) == sizeof(struct __kfifo))

This is weird. It's a compile-time constant. What's it here for?

> +
> +#define __kfifo_initializer(fifo) \
> + (typeof(fifo)) { \
> + { \
> + { \
> + .in = 0, \
> + .out = 0, \
> + .mask = __is_kfifo_ptr(&fifo) ? \
> + 0 : \
> + sizeof((fifo).buf)/sizeof(*(fifo).buf) - 1, \
> + .esize = sizeof(*(fifo).buf), \
> + .data = __is_kfifo_ptr(&fifo) ? \
> + NULL : \
> + (fifo).buf, \
> + } \
> + } \
> + }
> +
> +/*
> + * INIT_KFIFO - Initialize a fifo declared by DECLARE_KFIFO
> + * @fifo: name of the declared fifo datatype
> + */
> +#define INIT_KFIFO(fifo) fifo = __kfifo_initializer(fifo)

Some versions of gcc generate quite poor code for

struct foo f = { ... };

It would generate an instance of the struct into the stack and then
would memcpy it over, iirc. Please take a look, see if that's
happening with this construct (might need to use an old gcc version)
and if so, see if there's a fix?

> +/*
> + * DECLARE_KFIFO - macro to declare a fifo object
> + * @fifo: name of the declared fifo
> + * @type: type of the fifo elements
> + * @size: the number of elements in the fifo, this must be a power of 2.
> + */
> +#define DECLARE_KFIFO(fifo, type, size) STRUCT_KFIFO(type, size) fifo
> +
> +/*
> + * DEFINE_KFIFO - macro to define and initialize a fifo
> + * @fifo: name of the declared fifo datatype
> + * @type: type of the fifo elements
> + * @size: the number of elements in the fifo, this must be a power of 2.
> + *
> + * Note: the macro can be used for global and local fifo data type variables
> + */
> +#define DEFINE_KFIFO(fifo, type, size) \
> + DECLARE_KFIFO(fifo, type, size) = __kfifo_initializer(fifo)
> +
> +static inline unsigned int __must_check __kfifo_check(unsigned int val)
> +{
> + return val;
> +}

"check" is a poor term. Check what? For what? Unclear.

If I knew what this was supposed to check, I could suggest a better
name. But it's called "check", so I don't know :(

> +/*
> + * kfifo_initialized - Check if kfifo is initialized.
> + * @fifo: fifo to check
> + * Return %true if FIFO is initialized, otherwise %false.
> + * Assumes the fifo was 0 before.
> + *
> + * Note: for in place fifo's this macro returns alway true
> + */
> +#define kfifo_initialized(fifo) ((fifo)->kfifo.data != NULL)

kfifo_initialized() is suspicious. Any code which doesn't know whether
its kfifo was initialised is probably confused, lame and broken.
Fortunately kfifo_initialized() is not used anywhere. Please prepare a
separate patch to kill it sometime.

> +/*
> + * kfifo_esize - returns the size of the element managed by the fifo
> + * @fifo: the fifo to be used.
> + */
> +#define kfifo_esize(fifo) ((fifo)->kfifo.esize)

This doesn't seem to be used anywhere either.

> +/*
> + * kfifo_recsize - returns the size of the record length field
> + * @fifo: the fifo to be used.
> + */
> +#define kfifo_recsize(fifo) (sizeof(*(fifo)->rectype))

Neither is this. What's going on?

> +/*
> + * kfifo_size - returns the size of the fifo in elements
> + * @fifo: the fifo to be used.
> + */
> +#define kfifo_size(fifo) ((fifo)->kfifo.mask + 1)
> +
> +/*
> + * kfifo_reset - removes the entire fifo content
> + * @fifo: the fifo to be used.
> + *
> + * Note: usage of kfifo_reset() is dangerous. It should be only called when the
> + * fifo is exclusived locked or when it is secured that no other thread is
> + * accessing the fifo.
> + */
> +#define kfifo_reset(fifo) \
> +(void)({ \
> + typeof(fifo + 1) __tmp = (fifo); \

What does the "+ 1" trick do?

> + __tmp->kfifo.in = __tmp->kfifo.out = 0; \
> +})
> +
>
> ...
>
> +/*
> + * kfifo_put - put data into the fifo
> + * @fifo: the fifo to be used.
> + * @val: the data to be added.
> + *
> + * This macro copies the given value into the fifo.
> + *
> + * Note that with only one concurrent reader and one concurrent
> + * writer, you don't need extra locking to use these macro.

There are quite a few typos in the comments in this patch.

>
> ...
>
> +/*
> + * kfifo_out_locked - gets some data from the fifo using a spinlock for locking
> + * @fifo: the fifo to be used.
> + * @buf: pointer to the storage buffer
> + * @n: max. number of elements to get
> + * @lock: pointer to the spinlock to use for locking.
> + *
> + * This macro get the data from the fifo and return the numbers of elements
> + * copied.
> + */
> +#define kfifo_out_locked(fifo, buf, n, lock) \
> +__kfifo_check( \
> +({ \
> + unsigned long __flags; \
> + unsigned int __ret; \
> + spin_lock_irqsave(lock, __flags); \
> + __ret = kfifo_out(fifo, buf, n); \
> + spin_unlock_irqrestore(lock, __flags); \
> + __ret; \
> +}) \
> +)

This is poorly named. Generally "foo_locked" is to be called when the
caller has already taken the lock. This identifier inverts that
convention.

> +/*
> + * kfifo_from_user - puts some data from user space into the fifo
> + * @fifo: the fifo to be used.
> + * @from: pointer to the data to be added.
> + * @len: the length of the data to be added.
> + * @copied: pointer to output variable to store the number of copied bytes.
> + *
> + * This macro copies at most @len bytes from the @from into the
> + * fifo, depending of the available space and returns -EFAULT/0
> + *
> + * Note that with only one concurrent reader and one concurrent
> + * writer, you don't need extra locking to use these macro.
> + */
> +#define kfifo_from_user(fifo, from, len, copied) \
> +__kfifo_check( \
> +({ \
> + typeof(fifo + 1) __tmp = (fifo); \
> + const void __user *__from = (from); \
> + unsigned int __len = (len); \
> + unsigned int *__copied = (copied); \
> + const size_t __recsize = sizeof(*__tmp->rectype); \
> + struct __kfifo *__kfifo = &__tmp->kfifo; \
> + (__recsize) ? \
> + __kfifo_from_user_r(__kfifo, __from, __len, __copied, __recsize) : \
> + __kfifo_from_user(__kfifo, __from, __len, __copied); \
> +}) \
> +)
> +
> +/*
> + * kfifo_to_user - copies data from the fifo into user space
> + * @fifo: the fifo to be used.
> + * @to: where the data must be copied.
> + * @len: the size of the destination buffer.
> + * @copied: pointer to output variable to store the number of copied bytes.
> + *
> + * This macro copies at most @len bytes from the fifo into the
> + * @to buffer and returns -EFAULT/0.
> + *
> + * Note that with only one concurrent reader and one concurrent
> + * writer, you don't need extra locking to use these macro.
> + */
> +#define kfifo_to_user(fifo, to, len, copied) \
> +__kfifo_check( \
> +({ \
> + typeof(fifo + 1) __tmp = (fifo); \
> + void __user *__to = (to); \
> + unsigned int __len = (len); \
> + unsigned int *__copied = (copied); \
> + const size_t __recsize = sizeof(*__tmp->rectype); \
> + struct __kfifo *__kfifo = &__tmp->kfifo; \
> + (__recsize) ? \
> + __kfifo_to_user_r(__kfifo, __to, __len, __copied, __recsize) : \
> + __kfifo_to_user(__kfifo, __to, __len, __copied); \
> +}) \
> +)

Do these have any callers?

> +/*
> + * kfifo_dma_in_prepare - setup a scatterlist for DMA input
> + * @fifo: the fifo to be used.
> + * @sgl: pointer to the scatterlist array.
> + * @nents: number of entries in the scatterlist array
> + * @len: number of elements to transfer.
> + *
> + * This macro fills a scatterlist for DMA input.
> + * It returns the number entries in the scatterlist array
> + *
> + * Note that with only one concurrent reader and one concurrent
> + * writer, you don't need extra locking to use these macros.
> + */
> +#define kfifo_dma_in_prepare(fifo, sgl, nents, len) \
> +({ \
> + typeof(fifo + 1) __tmp = (fifo); \
> + struct scatterlist *__sgl = (sgl); \
> + int __nents = (nents); \
> + unsigned int __len = (len); \
> + const size_t __recsize = sizeof(*__tmp->rectype); \
> + struct __kfifo *__kfifo = &__tmp->kfifo; \
> + (__recsize) ? \
> + __kfifo_dma_in_prepare_r(__kfifo, __sgl, __nents, __len, __recsize) : \
> + __kfifo_dma_in_prepare(__kfifo,__sgl, __nents, __len); \
> +})

Do the DMA functions have any callers? If not, why was all this stuff
added?

>
> ...
>
> --- linux-2.6.33-rc5.dummy/kernel/kfifo.c 1970-01-01 01:00:00.000000000 +0100
> +++ linux-2.6.33-rc5.new/kernel/kfifo.c 2010-01-27 13:33:56.456825816 +0100
> @@ -0,0 +1,583 @@
> +/*
> + * A generic kernel FIFO implementation
> + *
> + * Copyright (C) 2009/2010 Stefani Seibold <[email protected]>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program; if not, write to the Free Software
> + * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
> + *
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/slab.h>
> +#include <linux/err.h>
> +#include <linux/kfifo.h>
> +#include <linux/log2.h>
> +#include <linux/uaccess.h>
> +
> +static unsigned int roundup_diff(unsigned int val, unsigned int size)
> +{
> + if (size <= 1)
> + return size;
> + return (val + size - 1) / size;
> +}

Would be useful to add a comment explaining why this exists.

Can we not use existing general facilities?

Should this be added to the existing general facilities?

> +static inline unsigned int kfifo_unused(struct __kfifo *fifo)
> +{
> + return (fifo->mask + 1) - (fifo->in - fifo->out);
> +}

hm, how does this differ from kfifo_avail()?

Should this use existing helpers such as kfifo_avail(), kfifo_len(),
etc?

> +int __kfifo_alloc(struct __kfifo *fifo, unsigned int size,
> + size_t esize, gfp_t gfp_mask)
> +{
> + /*
> + * round up to the next power of 2, since our 'let the indices
> + * wrap' technique works only in this case.
> + */
> + if (!is_power_of_2(size))
> + size = rounddown_pow_of_two(size);
> +
> + if (size < 2)
> + return -EINVAL;
> +
> + fifo->in = fifo->out = 0;

fifo->in = 0;
fifo->out = 0;

is usually preferred.

> + fifo->data = kmalloc(size * esize, gfp_mask);
> +
> + if (!fifo->data) {
> + fifo->mask = 0;
> + return -ENOMEM;
> + }
> +
> + fifo->mask = size - 1;
> + fifo->esize = esize;
> +
> + return 0;
> +}
> +EXPORT_SYMBOL(__kfifo_alloc);
> +
> +void __kfifo_free(struct __kfifo *fifo)
> +{
> + kfree(fifo);
> + fifo->data = 0;
> + fifo->mask = 0;
> + fifo->in = fifo->out = 0;
> +}
> +EXPORT_SYMBOL(__kfifo_free);

err, no. This scribbles on memory after having returned it to slab!

Which implies that this code wasn't tested with suitable kernel
debugging options enabled. Please absorb
Documentation/SubmitChecklist.

Initialising memory to zero just prior to freeing it is lame anyway.
And it can hide bugs. Just remove this and return the fifo to slab
as-is.

> +
> +int __kfifo_init(struct __kfifo *fifo, void *buffer,
> + unsigned int size, size_t esize)
> +{
> + size /= esize;
> +
> + if (size)
> + size = rounddown_pow_of_two(size);
> +
> + if (size < 2)
> + return -EINVAL;
> +
> + fifo->data = buffer;
> + fifo->in = fifo->out = 0;
> + fifo->mask = size - 1;
> + fifo->esize = esize;
> + return 0;
> +}
> +EXPORT_SYMBOL(__kfifo_init);
> +
> +static void kfifo_copy_in(struct __kfifo *fifo, const void *src,
> + unsigned int len, unsigned int off)
> +{
> + unsigned int size = fifo->mask + 1;
> + unsigned int esize = fifo->esize;
> + unsigned int l;
> +
> + off &= fifo->mask;
> + if (esize != 1) {
> + off *= esize;
> + size *= esize;
> + len *= esize;
> + }
> + l = min(len, size - off);
> +
> + memcpy(fifo->data + off, src, l);
> + memcpy(fifo->data, src + l, len - l);
> + smp_wmb();

It would be better if all the barriers in this code had comments
explaining why they're there. Looking at the above code it's quite
hard to determine which other code the barrier is protecting the data
against.

> +}
> +
>
> ...
>
> +static unsigned long kfifo_copy_from_user(struct __kfifo *fifo,
> + const void *src, unsigned int len, unsigned int off,
> + unsigned int *copied)
> +{
> + unsigned int size = fifo->mask + 1;
> + unsigned int esize = fifo->esize;
> + unsigned int l;
> + unsigned long ret;
> +
> + off &= fifo->mask;
> + if (esize != 1) {
> + off *= esize;
> + size *= esize;
> + len *= esize;
> + }
> + l = min(len, size - off);
> +
> + ret = copy_from_user(fifo->data + off, src, l);
> + if (unlikely(ret))
> + ret = roundup_diff(ret + len - l, esize);
> + else {
> + ret = copy_from_user(fifo->data, src + l, len - l);
> + if (unlikely(ret))
> + ret = roundup_diff(ret, esize);
> + }
> + smp_wmb();
> + if (copied)

Can `copied' ever be NULL? If not, remove this test.

> + *copied = len - ret;
> + return ret;
> +}

All pointers which refer to userspace should have the __user tag. And
the code should be checked with sparse, please.

It's rather hard to work out the meaning of this function's return value.

> +int __kfifo_from_user(struct __kfifo *fifo, const void __user *from,
> + unsigned long len, unsigned int *copied)
> +{
> + unsigned int l;
> + unsigned long ret;
> + unsigned int esize = fifo->esize;
> + int err;
> +
> + if (esize != 1)
> + len /= esize;
> +
> + l = kfifo_unused(fifo);
> + if (len > l)
> + len = l;
> +
> + ret = kfifo_copy_from_user(fifo, from, len, fifo->in, copied);
> + if (unlikely(ret)) {
> + len -= ret;
> + err = -EFAULT;
> + }
> + else
> + err = 0;
> + fifo->in += len;
> + return err;
> +}
> +EXPORT_SYMBOL(__kfifo_from_user);
> +
>
> ...
>
> +static int setup_sgl_buf(struct scatterlist *sgl, void *buf,
> + int nents, unsigned int len)
> +{
> + int n;
> + unsigned int l;
> + unsigned int off;
> + struct page *page;
> +
> + if (!nents)
> + return 0;
> +
> + if (!len)
> + return 0;
> +
> + n = 0;
> + page = virt_to_page(buf);
> + off = offset_in_page(buf);
> + l = 0;
> +
> + while(len >= l + PAGE_SIZE - off) {
> + struct page *npage;
> +
> + l += PAGE_SIZE;
> + buf += PAGE_SIZE;
> + npage = virt_to_page(buf);
> + if (page_to_phys(page) != page_to_phys(npage) - l) {
> + sgl->page_link = 0;
> + sg_set_page(sgl++, page, l - off, off);
> + if (++n == nents)
> + return n;
> + page = npage;
> + len -= l - off;
> + l = off = 0;
> + }
> + }
> + sgl->page_link = 0;
> + sg_set_page(sgl++, page, len, off);
> + return n + 1;
> +}

Again, I just don't see why all this sg and dma stuff is here. Has it
been tested?

>
> ...
>
> +/**
> + * __kfifo_peek_n internal helper function for determinate the length of
> + * the next record in the fifo
> + */

This comment purports to be kerneldoc ("/**") but it isn't.

> +static unsigned int __kfifo_peek_n(struct __kfifo *fifo, size_t recsize)
> +{
> + unsigned int l;
> + unsigned int mask = fifo->mask;
> + unsigned char *data = fifo->data;
> +
> + l = __KFIFO_PEEK(data, fifo->out, mask);
> +
> + if (--recsize)
> + l |= __KFIFO_PEEK(data, fifo->out + 1, mask) << 8;
> +
> + return l;
> +}
> +
> +#define __KFIFO_POKE(data, in, mask, val) \
> + ( \
> + (data)[(in) & (mask)] = (unsigned char)(val) \
> + )
> +
> +/**
> + * __kfifo_poke_n internal helper function for storeing the length of
> + * the record into the fifo
> + */

Please check all kerneldoc stuff.

>
> ...
>

2010-02-03 20:40:29

by Ira W. Snyder

Subject: Re: [PATCH] enhanced reimplemention of the kfifo API

On Wed, Feb 03, 2010 at 12:05:04PM -0800, Andrew Morton wrote:
> On Wed, 27 Jan 2010 14:00:43 +0100
> Stefani Seibold <[email protected]> wrote:
>
> > This is a complete reimplementation of the new kfifo API, which is now
> > really generic, type save and type definable.
> >
> >
> > ...
> >
> > diff -u -N -r -p linux-2.6.33-rc5.dummy/include/linux/kfifo.h linux-2.6.33-rc5.new/include/linux/kfifo.h
> > --- linux-2.6.33-rc5.dummy/include/linux/kfifo.h 1970-01-01 01:00:00.000000000 +0100
> > +++ linux-2.6.33-rc5.new/include/linux/kfifo.h 2010-01-27 13:34:06.324991898 +0100
> >
> > ...
> >
> > +/*
> > + * DECLARE_KFIFO_PTR - macro to declare a fifo pointer object
> > + * @fifo: name of the declared fifo
> > + * @type: type of the fifo elements
> > + * @size: the number of elements in the fifo, this must be a power of 2.
> > + */
>
> Throughout this patch the comments are in kerneldoc form, but they
> don't use the /** opening token, so the kerneldoc tools will ignore them.
>
> Please fix that up and test it.
>
> > +#define DECLARE_KFIFO_PTR(fifo, type) STRUCT_KFIFO_PTR(type) fifo
> > +
> > +/* helper macro */
> > +#define __is_kfifo_ptr(fifo) (sizeof(*fifo) == sizeof(struct __kfifo))
>
> This is weird. It's a compile-time constant. What's it here for?
>
> > +
> > +#define __kfifo_initializer(fifo) \
> > + (typeof(fifo)) { \
> > + { \
> > + { \
> > + .in = 0, \
> > + .out = 0, \
> > + .mask = __is_kfifo_ptr(&fifo) ? \
> > + 0 : \
> > + sizeof((fifo).buf)/sizeof(*(fifo).buf) - 1, \
> > + .esize = sizeof(*(fifo).buf), \
> > + .data = __is_kfifo_ptr(&fifo) ? \
> > + NULL : \
> > + (fifo).buf, \
> > + } \
> > + } \
> > + }
> > +
> > +/*
> > + * INIT_KFIFO - Initialize a fifo declared by DECLARE_KFIFO
> > + * @fifo: name of the declared fifo datatype
> > + */
> > +#define INIT_KFIFO(fifo) fifo = __kfifo_initializer(fifo)
>
> Some versions of gcc generate quite poor code for
>
> struct foo f = { ... };
>
> It would generate an instance of the struct into the stack and then
> would memcpy it over, iirc. Please take a look, see if that's
> happening with this construct (might need to use an old gcc version)
> and if so, see if there's a fix?
>
> > +/*
> > + * DECLARE_KFIFO - macro to declare a fifo object
> > + * @fifo: name of the declared fifo
> > + * @type: type of the fifo elements
> > + * @size: the number of elements in the fifo, this must be a power of 2.
> > + */
> > +#define DECLARE_KFIFO(fifo, type, size) STRUCT_KFIFO(type, size) fifo
> > +
> > +/*
> > + * DEFINE_KFIFO - macro to define and initialize a fifo
> > + * @fifo: name of the declared fifo datatype
> > + * @type: type of the fifo elements
> > + * @size: the number of elements in the fifo, this must be a power of 2.
> > + *
> > + * Note: the macro can be used for global and local fifo data type variables
> > + */
> > +#define DEFINE_KFIFO(fifo, type, size) \
> > + DECLARE_KFIFO(fifo, type, size) = __kfifo_initializer(fifo)
> > +
> > +static inline unsigned int __must_check __kfifo_check(unsigned int val)
> > +{
> > + return val;
> > +}
>
> "check" is a poor term. Check what? For what? Unclear.
>
> If I knew what this was supposed to check, I could suggest a better
> name. But it's called "check", so I don't know :(
>
> > +/*
> > + * kfifo_initialized - Check if kfifo is initialized.
> > + * @fifo: fifo to check
> > + * Return %true if FIFO is initialized, otherwise %false.
> > + * Assumes the fifo was 0 before.
> > + *
> > + * Note: for in place fifo's this macro returns alway true
> > + */
> > +#define kfifo_initialized(fifo) ((fifo)->kfifo.data != NULL)
>
> kfifo_initialized() is suspicious. Any code which doesn't know whether
> its kfifo was initialised is probably confused, lame and broken.
> Fortunately kfifo_initialized() is not used anywhere. Please prepare a
> separate patch to kill it sometime.
>
> > +/*
> > + * kfifo_esize - returns the size of the element managed by the fifo
> > + * @fifo: the fifo to be used.
> > + */
> > +#define kfifo_esize(fifo) ((fifo)->kfifo.esize)
>
> This doesn't seem to be used anywhere either.
>
> > +/*
> > + * kfifo_recsize - returns the size of the record length field
> > + * @fifo: the fifo to be used.
> > + */
> > +#define kfifo_recsize(fifo) (sizeof(*(fifo)->rectype))
>
> Neither is this. What's going on?
>
> > +/*
> > + * kfifo_size - returns the size of the fifo in elements
> > + * @fifo: the fifo to be used.
> > + */
> > +#define kfifo_size(fifo) ((fifo)->kfifo.mask + 1)
> > +
> > +/*
> > + * kfifo_reset - removes the entire fifo content
> > + * @fifo: the fifo to be used.
> > + *
> > + * Note: usage of kfifo_reset() is dangerous. It should be only called when the
> > + * fifo is exclusived locked or when it is secured that no other thread is
> > + * accessing the fifo.
> > + */
> > +#define kfifo_reset(fifo) \
> > +(void)({ \
> > + typeof(fifo + 1) __tmp = (fifo); \
>
> What does the "+ 1" trick do?
>
> > + __tmp->kfifo.in = __tmp->kfifo.out = 0; \
> > +})
> > +
> >
> > ...
> >
> > +/*
> > + * kfifo_put - put data into the fifo
> > + * @fifo: the fifo to be used.
> > + * @val: the data to be added.
> > + *
> > + * This macro copies the given value into the fifo.
> > + *
> > + * Note that with only one concurrent reader and one concurrent
> > + * writer, you don't need extra locking to use these macro.
>
> There are quite a few typos in the comments in this patch.
>
> >
> > ...
> >
> > +/*
> > + * kfifo_out_locked - gets some data from the fifo using a spinlock for locking
> > + * @fifo: the fifo to be used.
> > + * @buf: pointer to the storage buffer
> > + * @n: max. number of elements to get
> > + * @lock: pointer to the spinlock to use for locking.
> > + *
> > + * This macro get the data from the fifo and return the numbers of elements
> > + * copied.
> > + */
> > +#define kfifo_out_locked(fifo, buf, n, lock) \
> > +__kfifo_check( \
> > +({ \
> > + unsigned long __flags; \
> > + unsigned int __ret; \
> > + spin_lock_irqsave(lock, __flags); \
> > + __ret = kfifo_out(fifo, buf, n); \
> > + spin_unlock_irqrestore(lock, __flags); \
> > + __ret; \
> > +}) \
> > +)
>
> This is poorly named. Generally "foo_locked" is to be called when the
> caller has already taken the lock. This identifier inverts that
> convention.
>
> > +/*
> > + * kfifo_from_user - puts some data from user space into the fifo
> > + * @fifo: the fifo to be used.
> > + * @from: pointer to the data to be added.
> > + * @len: the length of the data to be added.
> > + * @copied: pointer to output variable to store the number of copied bytes.
> > + *
> > + * This macro copies at most @len bytes from the @from into the
> > + * fifo, depending of the available space and returns -EFAULT/0
> > + *
> > + * Note that with only one concurrent reader and one concurrent
> > + * writer, you don't need extra locking to use these macro.
> > + */
> > +#define kfifo_from_user(fifo, from, len, copied) \
> > +__kfifo_check( \
> > +({ \
> > + typeof(fifo + 1) __tmp = (fifo); \
> > + const void __user *__from = (from); \
> > + unsigned int __len = (len); \
> > + unsigned int *__copied = (copied); \
> > + const size_t __recsize = sizeof(*__tmp->rectype); \
> > + struct __kfifo *__kfifo = &__tmp->kfifo; \
> > + (__recsize) ? \
> > + __kfifo_from_user_r(__kfifo, __from, __len, __copied, __recsize) : \
> > + __kfifo_from_user(__kfifo, __from, __len, __copied); \
> > +}) \
> > +)
> > +
> > +/*
> > + * kfifo_to_user - copies data from the fifo into user space
> > + * @fifo: the fifo to be used.
> > + * @to: where the data must be copied.
> > + * @len: the size of the destination buffer.
> > + * @copied: pointer to output variable to store the number of copied bytes.
> > + *
> > + * This macro copies at most @len bytes from the fifo into the
> > + * @to buffer and returns -EFAULT/0.
> > + *
> > + * Note that with only one concurrent reader and one concurrent
> > + * writer, you don't need extra locking to use these macro.
> > + */
> > +#define kfifo_to_user(fifo, to, len, copied) \
> > +__kfifo_check( \
> > +({ \
> > + typeof(fifo + 1) __tmp = (fifo); \
> > + void __user *__to = (to); \
> > + unsigned int __len = (len); \
> > + unsigned int *__copied = (copied); \
> > + const size_t __recsize = sizeof(*__tmp->rectype); \
> > + struct __kfifo *__kfifo = &__tmp->kfifo; \
> > + (__recsize) ? \
> > + __kfifo_to_user_r(__kfifo, __to, __len, __copied, __recsize) : \
> > + __kfifo_to_user(__kfifo, __to, __len, __copied); \
> > +}) \
> > +)
>
> Do these have any callers?
>

As a driver author, I have use for these functions. I've basically
implemented a scatterlist_from_user() function in my own driver, which
isn't upstream yet. See below for more.

> > +/*
> > + * kfifo_dma_in_prepare - setup a scatterlist for DMA input
> > + * @fifo: the fifo to be used.
> > + * @sgl: pointer to the scatterlist array.
> > + * @nents: number of entries in the scatterlist array
> > + * @len: number of elements to transfer.
> > + *
> > + * This macro fills a scatterlist for DMA input.
> > + * It returns the number entries in the scatterlist array
> > + *
> > + * Note that with only one concurrent reader and one concurrent
> > + * writer, you don't need extra locking to use these macros.
> > + */
> > +#define kfifo_dma_in_prepare(fifo, sgl, nents, len) \
> > +({ \
> > + typeof(fifo + 1) __tmp = (fifo); \
> > + struct scatterlist *__sgl = (sgl); \
> > + int __nents = (nents); \
> > + unsigned int __len = (len); \
> > + const size_t __recsize = sizeof(*__tmp->rectype); \
> > + struct __kfifo *__kfifo = &__tmp->kfifo; \
> > + (__recsize) ? \
> > + __kfifo_dma_in_prepare_r(__kfifo, __sgl, __nents, __len, __recsize) : \
> > + __kfifo_dma_in_prepare(__kfifo,__sgl, __nents, __len); \
> > +})
>
> Do the DMA functions have any callers? If not, why was all this stuff
> added?
>

I have use for these too. The driver in question needs to retrieve an
FPGA bitfile from userspace, setup a DMA, and trigger the (hardware)
FPGA programming logic. The programming logic toggles the DMA pins
appropriately until the FPGA bitfile is loaded into the FPGA.

The driver isn't upstream, since it is only useful on my board, and no
other hardware in existence. I didn't think anyone would care. This
would remove my needs for a custom FIFO-ish type that I've invented on
top of a scatterlist, all so I could use dma_map_sg().

I have another driver which periodically reads (via DMA) from the FPGA
into a scatterlist. These scatterlists are buffered up until userspace
reads them via a char device. The driver essentially goes:

preallocate SG's
interrupt -> DMA to SG -> SG to userspace

I had to roll my own implementation to keep track of how much data had
been copied to userspace out of the buffer. Speaking as a driver author,
the new kfifo userspace and DMA API's would make my life just that much
easier.

Ira

> >
> > ...
> >
> > --- linux-2.6.33-rc5.dummy/kernel/kfifo.c 1970-01-01 01:00:00.000000000 +0100
> > +++ linux-2.6.33-rc5.new/kernel/kfifo.c 2010-01-27 13:33:56.456825816 +0100
> > @@ -0,0 +1,583 @@
> > +/*
> > + * A generic kernel FIFO implementation
> > + *
> > + * Copyright (C) 2009/2010 Stefani Seibold <[email protected]>
> > + *
> > + * This program is free software; you can redistribute it and/or modify
> > + * it under the terms of the GNU General Public License as published by
> > + * the Free Software Foundation; either version 2 of the License, or
> > + * (at your option) any later version.
> > + *
> > + * This program is distributed in the hope that it will be useful,
> > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> > + * GNU General Public License for more details.
> > + *
> > + * You should have received a copy of the GNU General Public License
> > + * along with this program; if not, write to the Free Software
> > + * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
> > + *
> > + */
> > +
> > +#include <linux/kernel.h>
> > +#include <linux/module.h>
> > +#include <linux/slab.h>
> > +#include <linux/err.h>
> > +#include <linux/kfifo.h>
> > +#include <linux/log2.h>
> > +#include <linux/uaccess.h>
> > +
> > +static unsigned int roundup_diff(unsigned int val, unsigned int size)
> > +{
> > + if (size <= 1)
> > + return size;
> > + return (val + size - 1) / size;
> > +}
>
> Would be useful to add a comment explaining why this exists.
>
> Can we not use existing general facilities?
>
> Should this be added to the existing general facilities?
>
> > +static inline unsigned int kfifo_unused(struct __kfifo *fifo)
> > +{
> > + return (fifo->mask + 1) - (fifo->in - fifo->out);
> > +}
>
> hm, how does this differ from kfifo_avail()?
>
> Should this use existing helpers such as kfifo_avail(), kfifo_len(),
> etc?
>
> > +int __kfifo_alloc(struct __kfifo *fifo, unsigned int size,
> > + size_t esize, gfp_t gfp_mask)
> > +{
> > + /*
> > + * round up to the next power of 2, since our 'let the indices
> > + * wrap' technique works only in this case.
> > + */
> > + if (!is_power_of_2(size))
> > + size = rounddown_pow_of_two(size);
> > +
> > + if (size < 2)
> > + return -EINVAL;
> > +
> > + fifo->in = fifo->out = 0;
>
> fifo->in = 0;
> fifo->out = 0;
>
> is usually preferred.
>
> > + fifo->data = kmalloc(size * esize, gfp_mask);
> > +
> > + if (!fifo->data) {
> > + fifo->mask = 0;
> > + return -ENOMEM;
> > + }
> > +
> > + fifo->mask = size - 1;
> > + fifo->esize = esize;
> > +
> > + return 0;
> > +}
> > +EXPORT_SYMBOL(__kfifo_alloc);
> > +
> > +void __kfifo_free(struct __kfifo *fifo)
> > +{
> > + kfree(fifo);
> > + fifo->data = 0;
> > + fifo->mask = 0;
> > + fifo->in = fifo->out = 0;
> > +}
> > +EXPORT_SYMBOL(__kfifo_free);
>
> err, no. This scribbles on memory after having returned it to slab!
>
> Which implies that this code wasn't tested with suitable kernel
> debugging options enabled. Please absorb
> Documentation/SubmitChecklist.
>
> Initialising memory to zero just prior to freeing it is lame anyway.
> And it can hide bugs. Just remove this and return the fifo to slab
> as-is.
>
> > +
> > +int __kfifo_init(struct __kfifo *fifo, void *buffer,
> > + unsigned int size, size_t esize)
> > +{
> > + size /= esize;
> > +
> > + if (size)
> > + size = rounddown_pow_of_two(size);
> > +
> > + if (size < 2)
> > + return -EINVAL;
> > +
> > + fifo->data = buffer;
> > + fifo->in = fifo->out = 0;
> > + fifo->mask = size - 1;
> > + fifo->esize = esize;
> > + return 0;
> > +}
> > +EXPORT_SYMBOL(__kfifo_init);
> > +
> > +static void kfifo_copy_in(struct __kfifo *fifo, const void *src,
> > + unsigned int len, unsigned int off)
> > +{
> > + unsigned int size = fifo->mask + 1;
> > + unsigned int esize = fifo->esize;
> > + unsigned int l;
> > +
> > + off &= fifo->mask;
> > + if (esize != 1) {
> > + off *= esize;
> > + size *= esize;
> > + len *= esize;
> > + }
> > + l = min(len, size - off);
> > +
> > + memcpy(fifo->data + off, src, l);
> > + memcpy(fifo->data, src + l, len - l);
> > + smp_wmb();
>
> It would be better if all the barriers in this code had comments
> explaining why they're there. Looking at the above code it's quite
> hard to determine which other code the barrier is protecting the data
> against.
>
> > +}
> > +
> >
> > ...
> >
> > +static unsigned long kfifo_copy_from_user(struct __kfifo *fifo,
> > + const void *src, unsigned int len, unsigned int off,
> > + unsigned int *copied)
> > +{
> > + unsigned int size = fifo->mask + 1;
> > + unsigned int esize = fifo->esize;
> > + unsigned int l;
> > + unsigned long ret;
> > +
> > + off &= fifo->mask;
> > + if (esize != 1) {
> > + off *= esize;
> > + size *= esize;
> > + len *= esize;
> > + }
> > + l = min(len, size - off);
> > +
> > + ret = copy_from_user(fifo->data + off, src, l);
> > + if (unlikely(ret))
> > + ret = roundup_diff(ret + len - l, esize);
> > + else {
> > + ret = copy_from_user(fifo->data, src + l, len - l);
> > + if (unlikely(ret))
> > + ret = roundup_diff(ret, esize);
> > + }
> > + smp_wmb();
> > + if (copied)
>
> Can `copied' ever be NULL? If not, remove this test.
>
> > + *copied = len - ret;
> > + return ret;
> > +}
>
> All pointers which refer to userspace should have the __user tag. And
> the code should be checked with sparse, please.
>
> It's rather hard to work out the meaning of this function's return value.
>
> > +int __kfifo_from_user(struct __kfifo *fifo, const void __user *from,
> > + unsigned long len, unsigned int *copied)
> > +{
> > + unsigned int l;
> > + unsigned long ret;
> > + unsigned int esize = fifo->esize;
> > + int err;
> > +
> > + if (esize != 1)
> > + len /= esize;
> > +
> > + l = kfifo_unused(fifo);
> > + if (len > l)
> > + len = l;
> > +
> > + ret = kfifo_copy_from_user(fifo, from, len, fifo->in, copied);
> > + if (unlikely(ret)) {
> > + len -= ret;
> > + err = -EFAULT;
> > + }
> > + else
> > + err = 0;
> > + fifo->in += len;
> > + return err;
> > +}
> > +EXPORT_SYMBOL(__kfifo_from_user);
> > +
> >
> > ...
> >
> > +static int setup_sgl_buf(struct scatterlist *sgl, void *buf,
> > + int nents, unsigned int len)
> > +{
> > + int n;
> > + unsigned int l;
> > + unsigned int off;
> > + struct page *page;
> > +
> > + if (!nents)
> > + return 0;
> > +
> > + if (!len)
> > + return 0;
> > +
> > + n = 0;
> > + page = virt_to_page(buf);
> > + off = offset_in_page(buf);
> > + l = 0;
> > +
> > + while(len >= l + PAGE_SIZE - off) {
> > + struct page *npage;
> > +
> > + l += PAGE_SIZE;
> > + buf += PAGE_SIZE;
> > + npage = virt_to_page(buf);
> > + if (page_to_phys(page) != page_to_phys(npage) - l) {
> > + sgl->page_link = 0;
> > + sg_set_page(sgl++, page, l - off, off);
> > + if (++n == nents)
> > + return n;
> > + page = npage;
> > + len -= l - off;
> > + l = off = 0;
> > + }
> > + }
> > + sgl->page_link = 0;
> > + sg_set_page(sgl++, page, len, off);
> > + return n + 1;
> > +}
>
> Again, I just don't see why all this sg and dma stuff is here. Has it
> been tested?
>
> >
> > ...
> >
> > +/**
> > + * __kfifo_peek_n internal helper function for determinate the length of
> > + * the next record in the fifo
> > + */
>
> This comment purports to be kerneldoc ("/**") but it isn't.
>
> > +static unsigned int __kfifo_peek_n(struct __kfifo *fifo, size_t recsize)
> > +{
> > + unsigned int l;
> > + unsigned int mask = fifo->mask;
> > + unsigned char *data = fifo->data;
> > +
> > + l = __KFIFO_PEEK(data, fifo->out, mask);
> > +
> > + if (--recsize)
> > + l |= __KFIFO_PEEK(data, fifo->out + 1, mask) << 8;
> > +
> > + return l;
> > +}
> > +
> > +#define __KFIFO_POKE(data, in, mask, val) \
> > + ( \
> > + (data)[(in) & (mask)] = (unsigned char)(val) \
> > + )
> > +
> > +/**
> > + * __kfifo_poke_n internal helper function for storeing the length of
> > + * the record into the fifo
> > + */
>
> Please check all kerneldoc stuff.
>
> >
> > ...
> >
>

2010-02-03 22:09:53

by Stefani Seibold

Subject: Re: [PATCH] enhanced reimplemention of the kfifo API

Am Mittwoch, den 03.02.2010, 12:05 -0800 schrieb Andrew Morton:
> On Wed, 27 Jan 2010 14:00:43 +0100
> Stefani Seibold <[email protected]> wrote:
>
> > This is a complete reimplementation of the new kfifo API, which is now
> > really generic, type save and type definable.
> >
> >
> > ...
> >
> > diff -u -N -r -p linux-2.6.33-rc5.dummy/include/linux/kfifo.h linux-2.6.33-rc5.new/include/linux/kfifo.h
> > --- linux-2.6.33-rc5.dummy/include/linux/kfifo.h 1970-01-01 01:00:00.000000000 +0100
> > +++ linux-2.6.33-rc5.new/include/linux/kfifo.h 2010-01-27 13:34:06.324991898 +0100
> >
> > ...
> >
> > +/*
> > + * DECLARE_KFIFO_PTR - macro to declare a fifo pointer object
> > + * @fifo: name of the declared fifo
> > + * @type: type of the fifo elements
> > + * @size: the number of elements in the fifo, this must be a power of 2.
> > + */
>
> Throughout this patch the comments are in kerneldoc form, but they
> don't use the /** opening token, so the kerneldoc tools will ignore them.
>
> Please fix that up and test it.
>
> > +#define DECLARE_KFIFO_PTR(fifo, type) STRUCT_KFIFO_PTR(type) fifo
> > +
> > +/* helper macro */
> > +#define __is_kfifo_ptr(fifo) (sizeof(*fifo) == sizeof(struct __kfifo))
>
> This is weird. It's a compile-time constant. What's it here for?

I need it to distinguish between real in place fifo, where the fifo
array is a part of the structure, and the fifo type where the array is
outside of the fifo structure.

>
> > +
> > +#define __kfifo_initializer(fifo) \
> > + (typeof(fifo)) { \
> > + { \
> > + { \
> > + .in = 0, \
> > + .out = 0, \
> > + .mask = __is_kfifo_ptr(&fifo) ? \
> > + 0 : \
> > + sizeof((fifo).buf)/sizeof(*(fifo).buf) - 1, \
> > + .esize = sizeof(*(fifo).buf), \
> > + .data = __is_kfifo_ptr(&fifo) ? \
> > + NULL : \
> > + (fifo).buf, \
> > + } \
> > + } \
> > + }
> > +

As you see it is used here for distinguish the initialization.

> > +/*
> > + * INIT_KFIFO - Initialize a fifo declared by DECLARE_KFIFO
> > + * @fifo: name of the declared fifo datatype
> > + */
> > +#define INIT_KFIFO(fifo) fifo = __kfifo_initializer(fifo)
>
> Some versions of gcc generate quite poor code for
>
> struct foo f = { ... };
>
> It would generate an instance of the struct into the stack and then
> would memcpy it over, iirc. Please take a look, see if that's
> happening with this construct (might need to use an old gcc version)
> and if so, see if there's a fix?
>

The current version of the kfifo implementation did it in the same way.
Why is it now wrong? Which gcc version do you mean?

> > +/*
> > + * DECLARE_KFIFO - macro to declare a fifo object
> > + * @fifo: name of the declared fifo
> > + * @type: type of the fifo elements
> > + * @size: the number of elements in the fifo, this must be a power of 2.
> > + */
> > +#define DECLARE_KFIFO(fifo, type, size) STRUCT_KFIFO(type, size) fifo
> > +
> > +/*
> > + * DEFINE_KFIFO - macro to define and initialize a fifo
> > + * @fifo: name of the declared fifo datatype
> > + * @type: type of the fifo elements
> > + * @size: the number of elements in the fifo, this must be a power of 2.
> > + *
> > + * Note: the macro can be used for global and local fifo data type variables
> > + */
> > +#define DEFINE_KFIFO(fifo, type, size) \
> > + DECLARE_KFIFO(fifo, type, size) = __kfifo_initializer(fifo)
> > +
> > +static inline unsigned int __must_check __kfifo_check(unsigned int val)
> > +{
> > + return val;
> > +}
>
> "check" is a poor term. Check what? For what? Unclear.
>
> If I knew what this was supposed to check, I could suggest a better
> name. But it's called "check", so I don't know :(
>

I will it rename to __kfifo_must_check_helper.

> > +/*
> > + * kfifo_initialized - Check if kfifo is initialized.
> > + * @fifo: fifo to check
> > + * Return %true if FIFO is initialized, otherwise %false.
> > + * Assumes the fifo was 0 before.
> > + *
> > + * Note: for in place fifo's this macro returns alway true
> > + */
> > +#define kfifo_initialized(fifo) ((fifo)->kfifo.data != NULL)
>
> kfifo_initialized() is suspicious. Any code which doesn't know whether
> its kfifo was initialised is probably confused, lame and broken.
> Fortunately kfifo_initialized() is not used anywhere. Please prepare a
> separate patch to kill it sometime.
>

This function was introduced as a patch by andi kleen and you have it
already applied.

> > +/*
> > + * kfifo_esize - returns the size of the element managed by the fifo
> > + * @fifo: the fifo to be used.
> > + */
> > +#define kfifo_esize(fifo) ((fifo)->kfifo.esize)
>
> This doesn't seem to be used anywhere either.
>

It is a part of the API. It returns the the size of the handled element,
If a driver developer need it, it is there.

> > +/*
> > + * kfifo_recsize - returns the size of the record length field
> > + * @fifo: the fifo to be used.
> > + */
> > +#define kfifo_recsize(fifo) (sizeof(*(fifo)->rectype))
>
> Neither is this. What's going on?
>

Dito... This returns the size of the record length field. 0 means this
is not a variable record fifo.

> > +/*
> > + * kfifo_size - returns the size of the fifo in elements
> > + * @fifo: the fifo to be used.
> > + */
> > +#define kfifo_size(fifo) ((fifo)->kfifo.mask + 1)
> > +
> > +/*
> > + * kfifo_reset - removes the entire fifo content
> > + * @fifo: the fifo to be used.
> > + *
> > + * Note: usage of kfifo_reset() is dangerous. It should be only called when the
> > + * fifo is exclusived locked or when it is secured that no other thread is
> > + * accessing the fifo.
> > + */
> > +#define kfifo_reset(fifo) \
> > +(void)({ \
> > + typeof(fifo + 1) __tmp = (fifo); \
>
> What does the "+ 1" trick do?
>

This is really a trick. Without this trick passing an array to the macro
will result in a compile error, because you can not copy an error in C.
But a typeof(array + 1) will result in a pointer and it is valid to
assign a pointer to address of an array.

> > + __tmp->kfifo.in = __tmp->kfifo.out = 0; \
> > +})
> > +
> >
> > ...
> >
> > +/*
> > + * kfifo_put - put data into the fifo
> > + * @fifo: the fifo to be used.
> > + * @val: the data to be added.
> > + *
> > + * This macro copies the given value into the fifo.
> > + *
> > + * Note that with only one concurrent reader and one concurrent
> > + * writer, you don't need extra locking to use these macro.
>
> There are quite a few typos in the comments in this patch.
>

Sorry, but my english far from perfect. Maybe someone could support
me ;-)

> >
> > ...
> >
> > +/*
> > + * kfifo_out_locked - gets some data from the fifo using a spinlock for locking
> > + * @fifo: the fifo to be used.
> > + * @buf: pointer to the storage buffer
> > + * @n: max. number of elements to get
> > + * @lock: pointer to the spinlock to use for locking.
> > + *
> > + * This macro get the data from the fifo and return the numbers of elements
> > + * copied.
> > + */
> > +#define kfifo_out_locked(fifo, buf, n, lock) \
> > +__kfifo_check( \
> > +({ \
> > + unsigned long __flags; \
> > + unsigned int __ret; \
> > + spin_lock_irqsave(lock, __flags); \
> > + __ret = kfifo_out(fifo, buf, n); \
> > + spin_unlock_irqrestore(lock, __flags); \
> > + __ret; \
> > +}) \
> > +)
>
> This is poorly named. Generally "foo_locked" is to be called when the
> caller has already taken the lock. This identifier inverts that
> convention.
>

This is the same name as the current kfifo API. Renaming it would break
a lot of drivers. But if there is no complain and you insist i will
rename it and fix the current users.

> > +/*
> > + * kfifo_from_user - puts some data from user space into the fifo
> > + * @fifo: the fifo to be used.
> > + * @from: pointer to the data to be added.
> > + * @len: the length of the data to be added.
> > + * @copied: pointer to output variable to store the number of copied bytes.
> > + *
> > + * This macro copies at most @len bytes from the @from into the
> > + * fifo, depending of the available space and returns -EFAULT/0
> > + *
> > + * Note that with only one concurrent reader and one concurrent
> > + * writer, you don't need extra locking to use these macro.
> > + */
> > +#define kfifo_from_user(fifo, from, len, copied) \
> > +__kfifo_check( \
> > +({ \
> > + typeof(fifo + 1) __tmp = (fifo); \
> > + const void __user *__from = (from); \
> > + unsigned int __len = (len); \
> > + unsigned int *__copied = (copied); \
> > + const size_t __recsize = sizeof(*__tmp->rectype); \
> > + struct __kfifo *__kfifo = &__tmp->kfifo; \
> > + (__recsize) ? \
> > + __kfifo_from_user_r(__kfifo, __from, __len, __copied, __recsize) : \
> > + __kfifo_from_user(__kfifo, __from, __len, __copied); \
> > +}) \
> > +)
> > +
> > +/*
> > + * kfifo_to_user - copies data from the fifo into user space
> > + * @fifo: the fifo to be used.
> > + * @to: where the data must be copied.
> > + * @len: the size of the destination buffer.
> > + * @copied: pointer to output variable to store the number of copied bytes.
> > + *
> > + * This macro copies at most @len bytes from the fifo into the
> > + * @to buffer and returns -EFAULT/0.
> > + *
> > + * Note that with only one concurrent reader and one concurrent
> > + * writer, you don't need extra locking to use these macro.
> > + */
> > +#define kfifo_to_user(fifo, to, len, copied) \
> > +__kfifo_check( \
> > +({ \
> > + typeof(fifo + 1) __tmp = (fifo); \
> > + void __user *__to = (to); \
> > + unsigned int __len = (len); \
> > + unsigned int *__copied = (copied); \
> > + const size_t __recsize = sizeof(*__tmp->rectype); \
> > + struct __kfifo *__kfifo = &__tmp->kfifo; \
> > + (__recsize) ? \
> > + __kfifo_to_user_r(__kfifo, __to, __len, __copied, __recsize) : \
> > + __kfifo_to_user(__kfifo, __to, __len, __copied); \
> > +}) \
> > +)
>
> Do these have any callers?
>

Currently not, but this is a part of the current kfifo implementation. A
lot of developer like this idea and it will be used in the near future.

> > +/*
> > + * kfifo_dma_in_prepare - setup a scatterlist for DMA input
> > + * @fifo: the fifo to be used.
> > + * @sgl: pointer to the scatterlist array.
> > + * @nents: number of entries in the scatterlist array
> > + * @len: number of elements to transfer.
> > + *
> > + * This macro fills a scatterlist for DMA input.
> > + * It returns the number entries in the scatterlist array
> > + *
> > + * Note that with only one concurrent reader and one concurrent
> > + * writer, you don't need extra locking to use these macros.
> > + */
> > +#define kfifo_dma_in_prepare(fifo, sgl, nents, len) \
> > +({ \
> > + typeof(fifo + 1) __tmp = (fifo); \
> > + struct scatterlist *__sgl = (sgl); \
> > + int __nents = (nents); \
> > + unsigned int __len = (len); \
> > + const size_t __recsize = sizeof(*__tmp->rectype); \
> > + struct __kfifo *__kfifo = &__tmp->kfifo; \
> > + (__recsize) ? \
> > + __kfifo_dma_in_prepare_r(__kfifo, __sgl, __nents, __len, __recsize) : \
> > + __kfifo_dma_in_prepare(__kfifo,__sgl, __nents, __len); \
> > +})
>
> Do the DMA functions have any callers? If not, why was all this stuff
> added?
>

It is the chicken and egg problem. Alan Cox, Ira W. Snyder and
Shargorodsky Ata wrote me that they like the idea, because they needed
this kind of functionality.

> >
> > ...
> >
> > --- linux-2.6.33-rc5.dummy/kernel/kfifo.c 1970-01-01 01:00:00.000000000 +0100
> > +++ linux-2.6.33-rc5.new/kernel/kfifo.c 2010-01-27 13:33:56.456825816 +0100
> > @@ -0,0 +1,583 @@
> > +/*
> > + * A generic kernel FIFO implementation
> > + *
> > + * Copyright (C) 2009/2010 Stefani Seibold <[email protected]>
> > + *
> > + * This program is free software; you can redistribute it and/or modify
> > + * it under the terms of the GNU General Public License as published by
> > + * the Free Software Foundation; either version 2 of the License, or
> > + * (at your option) any later version.
> > + *
> > + * This program is distributed in the hope that it will be useful,
> > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> > + * GNU General Public License for more details.
> > + *
> > + * You should have received a copy of the GNU General Public License
> > + * along with this program; if not, write to the Free Software
> > + * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
> > + *
> > + */
> > +
> > +#include <linux/kernel.h>
> > +#include <linux/module.h>
> > +#include <linux/slab.h>
> > +#include <linux/err.h>
> > +#include <linux/kfifo.h>
> > +#include <linux/log2.h>
> > +#include <linux/uaccess.h>
> > +
> > +static unsigned int roundup_diff(unsigned int val, unsigned int size)
> > +{
> > + if (size <= 1)
> > + return size;
> > + return (val + size - 1) / size;
> > +}
>
> Would be useful to add a comment explaining why this exists.
>
> Can we not use existing general facilities?
>
> Should this be added to the existing general facilities?
>

I will have a look on this.

> > +static inline unsigned int kfifo_unused(struct __kfifo *fifo)
> > +{
> > + return (fifo->mask + 1) - (fifo->in - fifo->out);
> > +}
>
> hm, how does this differ from kfifo_avail()?
>

This is similar to kfifo_avail, but due the nature of macro and type
conversation i have not longer the original type information available.
So i can't call the macros in kfifo.h from the functions defined in
kfifo.c.

> Should this use existing helpers such as kfifo_avail(), kfifo_len(),
> etc?
>

It wouldn't possible in most cases. See above.

> > +int __kfifo_alloc(struct __kfifo *fifo, unsigned int size,
> > + size_t esize, gfp_t gfp_mask)
> > +{
> > + /*
> > + * round up to the next power of 2, since our 'let the indices
> > + * wrap' technique works only in this case.
> > + */
> > + if (!is_power_of_2(size))
> > + size = rounddown_pow_of_two(size);
> > +
> > + if (size < 2)
> > + return -EINVAL;
> > +
> > + fifo->in = fifo->out = 0;
>
> fifo->in = 0;
> fifo->out = 0;
>
> is usually preferred.
>
> > + fifo->data = kmalloc(size * esize, gfp_mask);
> > +
> > + if (!fifo->data) {
> > + fifo->mask = 0;
> > + return -ENOMEM;
> > + }
> > +
> > + fifo->mask = size - 1;
> > + fifo->esize = esize;
> > +
> > + return 0;
> > +}
> > +EXPORT_SYMBOL(__kfifo_alloc);
> > +
> > +void __kfifo_free(struct __kfifo *fifo)
> > +{
> > + kfree(fifo);
> > + fifo->data = 0;
> > + fifo->mask = 0;
> > + fifo->in = fifo->out = 0;
> > +}
> > +EXPORT_SYMBOL(__kfifo_free);
>
> err, no. This scribbles on memory after having returned it to slab!
>

You found an bug. This should be kfree(fifo->data);

> Which implies that this code wasn't tested with suitable kernel
> debugging options enabled. Please absorb
> Documentation/SubmitChecklist.
>
> Initialising memory to zero just prior to freeing it is lame anyway.
> And it can hide bugs. Just remove this and return the fifo to slab
> as-is.
>
> > +
> > +int __kfifo_init(struct __kfifo *fifo, void *buffer,
> > + unsigned int size, size_t esize)
> > +{
> > + size /= esize;
> > +
> > + if (size)
> > + size = rounddown_pow_of_two(size);
> > +
> > + if (size < 2)
> > + return -EINVAL;
> > +
> > + fifo->data = buffer;
> > + fifo->in = fifo->out = 0;
> > + fifo->mask = size - 1;
> > + fifo->esize = esize;
> > + return 0;
> > +}
> > +EXPORT_SYMBOL(__kfifo_init);
> > +
> > +static void kfifo_copy_in(struct __kfifo *fifo, const void *src,
> > + unsigned int len, unsigned int off)
> > +{
> > + unsigned int size = fifo->mask + 1;
> > + unsigned int esize = fifo->esize;
> > + unsigned int l;
> > +
> > + off &= fifo->mask;
> > + if (esize != 1) {
> > + off *= esize;
> > + size *= esize;
> > + len *= esize;
> > + }
> > + l = min(len, size - off);
> > +
> > + memcpy(fifo->data + off, src, l);
> > + memcpy(fifo->data, src + l, len - l);
> > + smp_wmb();
>
> It would be better if all the barriers in this code had comments
> explaining why they're there. Looking at the above code it's quite
> hard to determine which other code the barrier is protecting the data
> against.
>

It should prevent to update the fifo counters, before the data in the
fifo are up to date.

> > +}
> > +
> >
> > ...
> >
> > +static unsigned long kfifo_copy_from_user(struct __kfifo *fifo,
> > + const void *src, unsigned int len, unsigned int off,
> > + unsigned int *copied)
> > +{
> > + unsigned int size = fifo->mask + 1;
> > + unsigned int esize = fifo->esize;
> > + unsigned int l;
> > + unsigned long ret;
> > +
> > + off &= fifo->mask;
> > + if (esize != 1) {
> > + off *= esize;
> > + size *= esize;
> > + len *= esize;
> > + }
> > + l = min(len, size - off);
> > +
> > + ret = copy_from_user(fifo->data + off, src, l);
> > + if (unlikely(ret))
> > + ret = roundup_diff(ret + len - l, esize);
> > + else {
> > + ret = copy_from_user(fifo->data, src + l, len - l);
> > + if (unlikely(ret))
> > + ret = roundup_diff(ret, esize);
> > + }
> > + smp_wmb();
> > + if (copied)
>
> Can `copied' ever be NULL? If not, remove this test.

It was only a feature. If you don't like i will remove it.

>
> > + *copied = len - ret;
> > + return ret;
> > +}
>
> All pointers which refer to userspace should have the __user tag. And
> the code should be checked with sparse, please.
>
> It's rather hard to work out the meaning of this function's return value.
>

I will add a comment.

> > +int __kfifo_from_user(struct __kfifo *fifo, const void __user *from,
> > + unsigned long len, unsigned int *copied)
> > +{
> > + unsigned int l;
> > + unsigned long ret;
> > + unsigned int esize = fifo->esize;
> > + int err;
> > +
> > + if (esize != 1)
> > + len /= esize;
> > +
> > + l = kfifo_unused(fifo);
> > + if (len > l)
> > + len = l;
> > +
> > + ret = kfifo_copy_from_user(fifo, from, len, fifo->in, copied);
> > + if (unlikely(ret)) {
> > + len -= ret;
> > + err = -EFAULT;
> > + }
> > + else
> > + err = 0;
> > + fifo->in += len;
> > + return err;
> > +}
> > +EXPORT_SYMBOL(__kfifo_from_user);
> > +
> >
> > ...
> >
> > +static int setup_sgl_buf(struct scatterlist *sgl, void *buf,
> > + int nents, unsigned int len)
> > +{
> > + int n;
> > + unsigned int l;
> > + unsigned int off;
> > + struct page *page;
> > +
> > + if (!nents)
> > + return 0;
> > +
> > + if (!len)
> > + return 0;
> > +
> > + n = 0;
> > + page = virt_to_page(buf);
> > + off = offset_in_page(buf);
> > + l = 0;
> > +
> > + while(len >= l + PAGE_SIZE - off) {
> > + struct page *npage;
> > +
> > + l += PAGE_SIZE;
> > + buf += PAGE_SIZE;
> > + npage = virt_to_page(buf);
> > + if (page_to_phys(page) != page_to_phys(npage) - l) {
> > + sgl->page_link = 0;
> > + sg_set_page(sgl++, page, l - off, off);
> > + if (++n == nents)
> > + return n;
> > + page = npage;
> > + len -= l - off;
> > + l = off = 0;
> > + }
> > + }
> > + sgl->page_link = 0;
> > + sg_set_page(sgl++, page, len, off);
> > + return n + 1;
> > +}
>
> Again, I just don't see why all this sg and dma stuff is here. Has it
> been tested?
>

See above. I had it tested. But maybe i do some things in a wrong way.
For me it works.

> >
> > ...
> >
> > +/**
> > + * __kfifo_peek_n internal helper function for determinate the length of
> > + * the next record in the fifo
> > + */
>
> This comment purports to be kerneldoc ("/**") but it isn't.
>

Will be fixed.

> > +static unsigned int __kfifo_peek_n(struct __kfifo *fifo, size_t recsize)
> > +{
> > + unsigned int l;
> > + unsigned int mask = fifo->mask;
> > + unsigned char *data = fifo->data;
> > +
> > + l = __KFIFO_PEEK(data, fifo->out, mask);
> > +
> > + if (--recsize)
> > + l |= __KFIFO_PEEK(data, fifo->out + 1, mask) << 8;
> > +
> > + return l;
> > +}
> > +
> > +#define __KFIFO_POKE(data, in, mask, val) \
> > + ( \
> > + (data)[(in) & (mask)] = (unsigned char)(val) \
> > + )
> > +
> > +/**
> > + * __kfifo_poke_n internal helper function for storeing the length of
> > + * the record into the fifo
> > + */
>
> Please check all kerneldoc stuff.
>

Ok.

2010-02-03 23:06:22

by Andrew Morton

Subject: Re: [PATCH] enhanced reimplemention of the kfifo API

On Wed, 03 Feb 2010 23:09:51 +0100
Stefani Seibold <[email protected]> wrote:

> Am Mittwoch, den 03.02.2010, 12:05 -0800 schrieb Andrew Morton:
> > On Wed, 27 Jan 2010 14:00:43 +0100
> > Stefani Seibold <[email protected]> wrote:
> >
> > > This is a complete reimplementation of the new kfifo API, which is now
> > > really generic, type save and type definable.
> > >
> > >
> > > ...
> > >
> > > diff -u -N -r -p linux-2.6.33-rc5.dummy/include/linux/kfifo.h linux-2.6.33-rc5.new/include/linux/kfifo.h
> > > --- linux-2.6.33-rc5.dummy/include/linux/kfifo.h 1970-01-01 01:00:00.000000000 +0100
> > > +++ linux-2.6.33-rc5.new/include/linux/kfifo.h 2010-01-27 13:34:06.324991898 +0100
> > >
> > > ...
> > >
> > > +/*
> > > + * DECLARE_KFIFO_PTR - macro to declare a fifo pointer object
> > > + * @fifo: name of the declared fifo
> > > + * @type: type of the fifo elements
> > > + * @size: the number of elements in the fifo, this must be a power of 2.
> > > + */
> >
> > Throughout this patch the comments are in kerneldoc form, but they
> > don't use the /** opening token, so the kerneldoc tools will ignore them.
> >
> > Please fix that up and test it.
> >
> > > +#define DECLARE_KFIFO_PTR(fifo, type) STRUCT_KFIFO_PTR(type) fifo
> > > +
> > > +/* helper macro */
> > > +#define __is_kfifo_ptr(fifo) (sizeof(*fifo) == sizeof(struct __kfifo))
> >
> > This is weird. It's a compile-time constant. What's it here for?
>
> I need it to distinguish between real in place fifo, where the fifo
> array is a part of the structure, and the fifo type where the array is
> outside of the fifo structure.

OK, please add a comment?

> > > +/*
> > > + * INIT_KFIFO - Initialize a fifo declared by DECLARE_KFIFO
> > > + * @fifo: name of the declared fifo datatype
> > > + */
> > > +#define INIT_KFIFO(fifo) fifo = __kfifo_initializer(fifo)
> >
> > Some versions of gcc generate quite poor code for
> >
> > struct foo f = { ... };
> >
> > It would generate an instance of the struct into the stack and then
> > would memcpy it over, iirc. Please take a look, see if that's
> > happening with this construct (might need to use an old gcc version)
> > and if so, see if there's a fix?
> >
>
> The current version of the kfifo implementation did it in the same way.
> Why is it now wrong?

It was wrong before, too.

> Which gcc version do you mean?

I don't recall. The oldest gcc the kernel permits is 3.2, so checking
any 3.x should be OK.

> > > +/*
> > > + * kfifo_initialized - Check if kfifo is initialized.
> > > + * @fifo: fifo to check
> > > + * Return %true if FIFO is initialized, otherwise %false.
> > > + * Assumes the fifo was 0 before.
> > > + *
> > > + * Note: for in place fifo's this macro returns alway true
> > > + */
> > > +#define kfifo_initialized(fifo) ((fifo)->kfifo.data != NULL)
> >
> > kfifo_initialized() is suspicious. Any code which doesn't know whether
> > its kfifo was initialised is probably confused, lame and broken.
> > Fortunately kfifo_initialized() is not used anywhere. Please prepare a
> > separate patch to kill it sometime.
> >
>
> This function was introduced as a patch by andi kleen and you have it
> already applied.

Let's delete it?

> > > +/*
> > > + * kfifo_esize - returns the size of the element managed by the fifo
> > > + * @fifo: the fifo to be used.
> > > + */
> > > +#define kfifo_esize(fifo) ((fifo)->kfifo.esize)
> >
> > This doesn't seem to be used anywhere either.
> >
>
> It is a part of the API. It returns the the size of the handled element,
> If a driver developer need it, it is there.

Well, if there's no proven need for it now, it will remain dead code
for an unknown period of time.

Also, there was no need to implement this as a macro (was there?). If
not, conversion to a more typesafe C function would be better.

> > > +/*
> > > + * kfifo_recsize - returns the size of the record length field
> > > + * @fifo: the fifo to be used.
> > > + */
> > > +#define kfifo_recsize(fifo) (sizeof(*(fifo)->rectype))
> >
> > Neither is this. What's going on?
> >
>
> Dito... This returns the size of the record length field. 0 means this
> is not a variable record fifo.

ditto.

> > > +/*
> > > + * kfifo_out_locked - gets some data from the fifo using a spinlock for locking
> > > + * @fifo: the fifo to be used.
> > > + * @buf: pointer to the storage buffer
> > > + * @n: max. number of elements to get
> > > + * @lock: pointer to the spinlock to use for locking.
> > > + *
> > > + * This macro get the data from the fifo and return the numbers of elements
> > > + * copied.
> > > + */
> > > +#define kfifo_out_locked(fifo, buf, n, lock) \
> > > +__kfifo_check( \
> > > +({ \
> > > + unsigned long __flags; \
> > > + unsigned int __ret; \
> > > + spin_lock_irqsave(lock, __flags); \
> > > + __ret = kfifo_out(fifo, buf, n); \
> > > + spin_unlock_irqrestore(lock, __flags); \
> > > + __ret; \
> > > +}) \
> > > +)
> >
> > This is poorly named. Generally "foo_locked" is to be called when the
> > caller has already taken the lock. This identifier inverts that
> > convention.
> >
>
> This is the same name as the current kfifo API. Renaming it would break
> a lot of drivers. But if there is no complain and you insist i will
> rename it and fix the current users.

argh, we goofed.

yeah, it'd be nice to fix it sometime, please. Not urgent.

A good way to fix it would be to add a new function with a new name
then migrate all callers over to that name then when it's done, remove
the old name.

> > > + * @fifo: the fifo to be used.
> > > + * @to: where the data must be copied.
> > > + * @len: the size of the destination buffer.
> > > + * @copied: pointer to output variable to store the number of copied bytes.
> > > + *
> > > + * This macro copies at most @len bytes from the fifo into the
> > > + * @to buffer and returns -EFAULT/0.
> > > + *
> > > + * Note that with only one concurrent reader and one concurrent
> > > + * writer, you don't need extra locking to use these macro.
> > > + */
> > > +#define kfifo_to_user(fifo, to, len, copied) \
> > > +__kfifo_check( \
> > > +({ \
> > > + typeof(fifo + 1) __tmp = (fifo); \
> > > + void __user *__to = (to); \
> > > + unsigned int __len = (len); \
> > > + unsigned int *__copied = (copied); \
> > > + const size_t __recsize = sizeof(*__tmp->rectype); \
> > > + struct __kfifo *__kfifo = &__tmp->kfifo; \
> > > + (__recsize) ? \
> > > + __kfifo_to_user_r(__kfifo, __to, __len, __copied, __recsize) : \
> > > + __kfifo_to_user(__kfifo, __to, __len, __copied); \
> > > +}) \
> > > +)
> >
> > Do these have any callers?
> >
>
> Currently not, but this is a part of the current kfifo implementation. A
> lot of developer like this idea and it will be used in the near future.

OK. Please describe the presently-unused interfaces in the changelog,
with particular attention to the reason for including them at this
time.

> > > +static inline unsigned int kfifo_unused(struct __kfifo *fifo)
> > > +{
> > > + return (fifo->mask + 1) - (fifo->in - fifo->out);
> > > +}
> >
> > hm, how does this differ from kfifo_avail()?
> >
>
> This is similar to kfifo_avail, but due the nature of macro and type
> conversation i have not longer the original type information available.
> So i can't call the macros in kfifo.h from the functions defined in
> kfifo.c.

OK, please add a comment there. (As a general rule: if this reader
needed more info then other readers will want more info as well).

> > > +static unsigned long kfifo_copy_from_user(struct __kfifo *fifo,
> > > + const void *src, unsigned int len, unsigned int off,
> > > + unsigned int *copied)
> > > +{
> > > + unsigned int size = fifo->mask + 1;
> > > + unsigned int esize = fifo->esize;
> > > + unsigned int l;
> > > + unsigned long ret;
> > > +
> > > + off &= fifo->mask;
> > > + if (esize != 1) {
> > > + off *= esize;
> > > + size *= esize;
> > > + len *= esize;
> > > + }
> > > + l = min(len, size - off);
> > > +
> > > + ret = copy_from_user(fifo->data + off, src, l);
> > > + if (unlikely(ret))
> > > + ret = roundup_diff(ret + len - l, esize);
> > > + else {
> > > + ret = copy_from_user(fifo->data, src + l, len - l);
> > > + if (unlikely(ret))
> > > + ret = roundup_diff(ret, esize);
> > > + }
> > > + smp_wmb();
> > > + if (copied)
> >
> > Can `copied' ever be NULL? If not, remove this test.
>
> It was only a feature. If you don't like i will remove it.

No strong opinion. But if present callers don't pass NULL then that's
a sign that future callers won't, too. We may as well save the
speed/space overhead until we actually need it.

2010-02-04 16:52:36

by Stefani Seibold

Subject: Re: [PATCH] enhanced reimplemention of the kfifo API

Am Mittwoch, den 03.02.2010, 15:05 -0800 schrieb Andrew Morton:
> On Wed, 03 Feb 2010 23:09:51 +0100
> Stefani Seibold <[email protected]> wrote:
>
> > Am Mittwoch, den 03.02.2010, 12:05 -0800 schrieb Andrew Morton:
> > > On Wed, 27 Jan 2010 14:00:43 +0100
> > > Stefani Seibold <[email protected]> wrote:
> > >
> > > > This is a complete reimplementation of the new kfifo API, which is now
> > > > really generic, type save and type definable.
> > > >
> > > >
> > > > ...
> > > >
> > > > diff -u -N -r -p linux-2.6.33-rc5.dummy/include/linux/kfifo.h linux-2.6.33-rc5.new/include/linux/kfifo.h
> > > > --- linux-2.6.33-rc5.dummy/include/linux/kfifo.h 1970-01-01 01:00:00.000000000 +0100
> > > > +++ linux-2.6.33-rc5.new/include/linux/kfifo.h 2010-01-27 13:34:06.324991898 +0100
> > > >
> > > > ...
> > > >
> > > > +/*
> > > > + * DECLARE_KFIFO_PTR - macro to declare a fifo pointer object
> > > > + * @fifo: name of the declared fifo
> > > > + * @type: type of the fifo elements
> > > > + * @size: the number of elements in the fifo, this must be a power of 2.
> > > > + */
> > >
> > > Throughout this patch the comments are in kerneldoc form, but they
> > > don't use the /** opening token, so the kerneldoc tools will ignore them.
> > >
> > > Please fix that up and test it.
> > >
> > > > +#define DECLARE_KFIFO_PTR(fifo, type) STRUCT_KFIFO_PTR(type) fifo
> > > > +
> > > > +/* helper macro */
> > > > +#define __is_kfifo_ptr(fifo) (sizeof(*fifo) == sizeof(struct __kfifo))
> > >
> > > This is weird. It's a compile-time constant. What's it here for?
> >
> > I need it to distinguish between real in place fifo, where the fifo
> > array is a part of the structure, and the fifo type where the array is
> > outside of the fifo structure.
>
> OK, please add a comment?

I will do this.

>
> > > > +/*
> > > > + * INIT_KFIFO - Initialize a fifo declared by DECLARE_KFIFO
> > > > + * @fifo: name of the declared fifo datatype
> > > > + */
> > > > +#define INIT_KFIFO(fifo) fifo = __kfifo_initializer(fifo)
> > >
> > > Some versions of gcc generate quite poor code for
> > >
> > > struct foo f = { ... };
> > >
> > > It would generate an instance of the struct into the stack and then
> > > would memcpy it over, iirc. Please take a look, see if that's
> > > happening with this construct (might need to use an old gcc version)
> > > and if so, see if there's a fix?
> > >
> >
> > The current version of the kfifo implementation did it in the same way.
> > Why is it now wrong?
>
> It was wrong before, too.
>
> > Which gcc version do you mean?
>
> I don't recall. The oldest gcc the kernel permits is 3.2, so checking
> any 3.x should be OK.
>

I will try to build a gcc 3 and check it.

> > > > +/*
> > > > + * kfifo_initialized - Check if kfifo is initialized.
> > > > + * @fifo: fifo to check
> > > > + * Return %true if FIFO is initialized, otherwise %false.
> > > > + * Assumes the fifo was 0 before.
> > > > + *
> > > > + * Note: for in place fifo's this macro returns alway true
> > > > + */
> > > > +#define kfifo_initialized(fifo) ((fifo)->kfifo.data != NULL)
> > >
> > > kfifo_initialized() is suspicious. Any code which doesn't know whether
> > > its kfifo was initialised is probably confused, lame and broken.
> > > Fortunately kfifo_initialized() is not used anywhere. Please prepare a
> > > separate patch to kill it sometime.
> > >
> >
> > This function was introduced as a patch by andi kleen and you have it
> > already applied.
>
> Let's delete it?
>

Can you clarify this with andi please?

> > > > +/*
> > > > + * kfifo_esize - returns the size of the element managed by the fifo
> > > > + * @fifo: the fifo to be used.
> > > > + */
> > > > +#define kfifo_esize(fifo) ((fifo)->kfifo.esize)
> > >
> > > This doesn't seem to be used anywhere either.
> > >
> >
> > It is a part of the API. It returns the the size of the handled element,
> > If a driver developer need it, it is there.
>
> Well, if there's no proven need for it now, it will remain dead code
> for an unknown period of time.
>
> Also, there was no need to implement this as a macro (was there?). If
> not, conversion to a more typesafe C function would be better.
>

It is not possible to write this as a function, because the parameter
fifo is an arbitrary type. There is no fifo type, only a template and a
macro which generates a fifo which managed a given type, where the
generic "struct __kfifo" part is embedded.

> > > > +/*
> > > > + * kfifo_recsize - returns the size of the record length field
> > > > + * @fifo: the fifo to be used.
> > > > + */
> > > > +#define kfifo_recsize(fifo) (sizeof(*(fifo)->rectype))
> > >
> > > Neither is this. What's going on?
> > >
> >
> > Dito... This returns the size of the record length field. 0 means this
> > is not a variable record fifo.
>
> ditto.
>
> > > > +/*
> > > > + * kfifo_out_locked - gets some data from the fifo using a spinlock for locking
> > > > + * @fifo: the fifo to be used.
> > > > + * @buf: pointer to the storage buffer
> > > > + * @n: max. number of elements to get
> > > > + * @lock: pointer to the spinlock to use for locking.
> > > > + *
> > > > + * This macro get the data from the fifo and return the numbers of elements
> > > > + * copied.
> > > > + */
> > > > +#define kfifo_out_locked(fifo, buf, n, lock) \
> > > > +__kfifo_check( \
> > > > +({ \
> > > > + unsigned long __flags; \
> > > > + unsigned int __ret; \
> > > > + spin_lock_irqsave(lock, __flags); \
> > > > + __ret = kfifo_out(fifo, buf, n); \
> > > > + spin_unlock_irqrestore(lock, __flags); \
> > > > + __ret; \
> > > > +}) \
> > > > +)
> > >
> > > This is poorly named. Generally "foo_locked" is to be called when the
> > > caller has already taken the lock. This identifier inverts that
> > > convention.
> > >
> >
> > This is the same name as the current kfifo API. Renaming it would break
> > a lot of drivers. But if there is no complain and you insist i will
> > rename it and fix the current users.
>
> argh, we goofed.
>
> yeah, it'd be nice to fix it sometime, please. Not urgent.
>
> A good way to fix it would be to add a new function with a new name
> then migrate all callers over to that name then when it's done, remove
> the old name.
>

I will do this in the next release. Would be kfifo_out_spinlocked() and
kfifo_in_spinlocked() for the new names okay?

> > > > + * @fifo: the fifo to be used.
> > > > + * @to: where the data must be copied.
> > > > + * @len: the size of the destination buffer.
> > > > + * @copied: pointer to output variable to store the number of copied bytes.
> > > > + *
> > > > + * This macro copies at most @len bytes from the fifo into the
> > > > + * @to buffer and returns -EFAULT/0.
> > > > + *
> > > > + * Note that with only one concurrent reader and one concurrent
> > > > + * writer, you don't need extra locking to use these macro.
> > > > + */
> > > > +#define kfifo_to_user(fifo, to, len, copied) \
> > > > +__kfifo_check( \
> > > > +({ \
> > > > + typeof(fifo + 1) __tmp = (fifo); \
> > > > + void __user *__to = (to); \
> > > > + unsigned int __len = (len); \
> > > > + unsigned int *__copied = (copied); \
> > > > + const size_t __recsize = sizeof(*__tmp->rectype); \
> > > > + struct __kfifo *__kfifo = &__tmp->kfifo; \
> > > > + (__recsize) ? \
> > > > + __kfifo_to_user_r(__kfifo, __to, __len, __copied, __recsize) : \
> > > > + __kfifo_to_user(__kfifo, __to, __len, __copied); \
> > > > +}) \
> > > > +)
> > >
> > > Do these have any callers?
> > >
> >
> > Currently not, but this is a part of the current kfifo implementation. A
> > lot of developer like this idea and it will be used in the near future.
>
> OK. Please describe the presently-unused interfaces in the changelog,
> with particular attention to the reason for including them at this
> time.
>

OK

> > > > +static inline unsigned int kfifo_unused(struct __kfifo *fifo)
> > > > +{
> > > > + return (fifo->mask + 1) - (fifo->in - fifo->out);
> > > > +}
> > >
> > > hm, how does this differ from kfifo_avail()?
> > >
> >
> > This is similar to kfifo_avail, but due the nature of macro and type
> > conversation i have not longer the original type information available.
> > So i can't call the macros in kfifo.h from the functions defined in
> > kfifo.c.
>
> OK, please add a comment there. (As a general rule: if this reader
> needed more info then other readers will want more info as well).
>
> > > > +static unsigned long kfifo_copy_from_user(struct __kfifo *fifo,
> > > > + const void *src, unsigned int len, unsigned int off,
> > > > + unsigned int *copied)
> > > > +{
> > > > + unsigned int size = fifo->mask + 1;
> > > > + unsigned int esize = fifo->esize;
> > > > + unsigned int l;
> > > > + unsigned long ret;
> > > > +
> > > > + off &= fifo->mask;
> > > > + if (esize != 1) {
> > > > + off *= esize;
> > > > + size *= esize;
> > > > + len *= esize;
> > > > + }
> > > > + l = min(len, size - off);
> > > > +
> > > > + ret = copy_from_user(fifo->data + off, src, l);
> > > > + if (unlikely(ret))
> > > > + ret = roundup_diff(ret + len - l, esize);
> > > > + else {
> > > > + ret = copy_from_user(fifo->data, src + l, len - l);
> > > > + if (unlikely(ret))
> > > > + ret = roundup_diff(ret, esize);
> > > > + }
> > > > + smp_wmb();
> > > > + if (copied)
> > >
> > > Can `copied' ever be NULL? If not, remove this test.
> >
> > It was only a feature. If you don't like i will remove it.
>
> No strong opinion. But if present callers don't pass NULL then that's
> a sign that future callers won't, too. We may as well save the
> speed/space overhead until we actually need it.
>
>

This will be fixed in the next release.

One offer to solve the egg and chicken problem: Let us include the
functions kfifo_to_user(), kfifo_from_user(), kfifo_esize(),
kfifo_recsize() and the dynamic record handling. If there will be no
users in at least 9 months we remove it from the API. We talk here about
400 bytes of code.

In the mean time me and other developer will have a change to modify the
existing driver to the new API and/or post drivers or core kernel code
which is using this functionality.

Stefani

2010-02-04 17:59:52

by Andrew Morton

Subject: Re: [PATCH] enhanced reimplemention of the kfifo API

On Thu, 04 Feb 2010 17:52:40 +0100
Stefani Seibold <[email protected]> wrote:

> ...
> > > > > +#define kfifo_out_locked(fifo, buf, n, lock) \
> > > > > +__kfifo_check( \
> > > > > +({ \
> > > > > + unsigned long __flags; \
> > > > > + unsigned int __ret; \
> > > > > + spin_lock_irqsave(lock, __flags); \
> > > > > + __ret = kfifo_out(fifo, buf, n); \
> > > > > + spin_unlock_irqrestore(lock, __flags); \
> > > > > + __ret; \
> > > > > +}) \
> > > > > +)
> > > >
> > > > This is poorly named. Generally "foo_locked" is to be called when the
> > > > caller has already taken the lock. This identifier inverts that
> > > > convention.
> > > >
> > >
> > > This is the same name as the current kfifo API. Renaming it would break
> > > a lot of drivers. But if there is no complain and you insist i will
> > > rename it and fix the current users.
> >
> > argh, we goofed.
> >
> > yeah, it'd be nice to fix it sometime, please. Not urgent.
> >
> > A good way to fix it would be to add a new function with a new name
> > then migrate all callers over to that name then when it's done, remove
> > the old name.
> >
>
> I will do this in the next release. Would be kfifo_out_spinlocked() and
> kfifo_in_spinlocked() for the new names okay?

Good enough. It's a bit sad to needlessly expose the type of lock in
the identifier but not the end of the world.

>
> One offer to solve the egg and chicken problem: Let us include the
> functions kfifo_to_user(), kfifo_from_user(), kfifo_esize(),
> kfifo_recsize() and the dynamic record handling. If there will be no
> users in at least 9 months we remove it from the API. We talk here about
> 400 bytes of code.
>
> In the mean time me and other developer will have a change to modify the
> existing driver to the new API and/or post drivers or core kernel code
> which is using this functionality.
>

Sounds OK to me.