Media drivers that control a single media TV stick are a
diversified group. Analog and digital TV function drivers have
to coordinate access to their shared functions. In some cases,
snd-usb-audio is used to support audio function on media devices.
A shared managed resource framework at drivers/base level will
allow a media device to be controlled by drivers that don't
fall under drivers/media and share functions with other media
drivers.
A token devres that can be looked up by a token for locking, try
locking, unlocking will help avoid adding data structure
dependencies between various drivers. This token is a unique
string that can be constructed from a common data structure such as
struct device, bus_name, and hardware address.
This patch series adds devm_token_* interfaces to manage access to
token resource and a tuner token to allow sharing tuner function
across analog and digital functions. em28xx and dvb-core make
use of this new tuner token to control tuner access. Analog changes
will be added in a subsequent patch series.
Patch series is tested with Kworld UB435-Q V3 USB TV stick and
Kaffeine media player.
Shuah Khan (4):
drivers/base: add managed token devres interfaces
media: dvb-fe changes to use token for shared access control
media/em28xx: changes to create token for tuner access
media: em28xx dvb changes to initialze dvb fe tuner token
drivers/base/Makefile | 2 +-
drivers/base/token_devres.c | 146 +++++++++++++++++++++++++++++++
drivers/media/dvb-core/dvb_frontend.c | 15 ++++
drivers/media/dvb-core/dvb_frontend.h | 1 +
drivers/media/usb/em28xx/em28xx-cards.c | 41 +++++++++
drivers/media/usb/em28xx/em28xx-dvb.c | 4 +
drivers/media/usb/em28xx/em28xx.h | 4 +
include/linux/token_devres.h | 19 ++++
8 files changed, 231 insertions(+), 1 deletion(-)
create mode 100644 drivers/base/token_devres.c
create mode 100644 include/linux/token_devres.h
--
1.7.10.4
Media devices often have hardware resources that are shared
across several functions. These devices appear as a group of
independent devices. Each device implements a function which
could be shared by one or more functions supported by the same
device. For example, tuner is shared by analog and digital TV
functions.
Media drivers that control a single media TV stick are a
diversified group. Analog and digital TV function drivers have
to coordinate access to their shared functions.
Some media devices provide multiple almost-independent functions.
USB and PCI core aids in allowwing multiple drivers to handle these
almost-independent functions. In this model, a em28xx device could
have snd-usb-audio driving the audio function.
As a result, snd-usb-audio driver has to coordinate with the em28xx_*
analog and digital function drivers.
A shared managed resource framework at drivers/base level will
allow a media device to be controlled by drivers that don't
fall under drivers/media and share functions with other media
drivers.
A token devres that can be looked up by a token for locking, try
locking, unlocking will help avoid adding data structure
dependencies between various drivers. This token is a unique
string that can be constructed from a common data structure such as
struct device, bus_name, and hardware address.
The devm_token_* interfaces manage access to token resource.
Interfaces:
devm_token_create()
devm_token_destroy()
devm_token_lock()
devm_token_unlock()
Usage:
Create token: Call devm_token_create() with a token id string.
Lock token: Call devm_token_lock() to lock or try lock a token.
Unlock token: Call devm_token_unlock().
Destroy token: Call devm_token_destroy() to delete the token.
Signed-off-by: Shuah Khan <[email protected]>
---
drivers/base/Makefile | 2 +-
drivers/base/token_devres.c | 146 ++++++++++++++++++++++++++++++++++++++++++
include/linux/token_devres.h | 19 ++++++
3 files changed, 166 insertions(+), 1 deletion(-)
create mode 100644 drivers/base/token_devres.c
create mode 100644 include/linux/token_devres.h
diff --git a/drivers/base/Makefile b/drivers/base/Makefile
index 04b314e..924665b 100644
--- a/drivers/base/Makefile
+++ b/drivers/base/Makefile
@@ -4,7 +4,7 @@ obj-y := component.o core.o bus.o dd.o syscore.o \
driver.o class.o platform.o \
cpu.o firmware.o init.o map.o devres.o \
attribute_container.o transport_class.o \
- topology.o container.o
+ topology.o container.o token_devres.o
obj-$(CONFIG_DEVTMPFS) += devtmpfs.o
obj-$(CONFIG_DMA_CMA) += dma-contiguous.o
obj-y += power/
diff --git a/drivers/base/token_devres.c b/drivers/base/token_devres.c
new file mode 100644
index 0000000..4644642
--- /dev/null
+++ b/drivers/base/token_devres.c
@@ -0,0 +1,146 @@
+/*
+ * drivers/base/token_devres.c - managed token resource
+ *
+ * Copyright (c) 2014 Shuah Khan <[email protected]>
+ * Copyright (c) 2014 Samsung Electronics Co., Ltd.
+ *
+ * This file is released under the GPLv2.
+ */
+/*
+ * Media devices often have hardware resources that are shared
+ * across several functions. For instance, TV tuner cards often
+ * have MUXes, converters, radios, tuners, etc. that are shared
+ * across various functions. However, v4l2, alsa, DVB, usbfs, and
+ * all other drivers have no knowledge of what resources are
+ * shared. For example, users can't access DVB and alsa at the same
+ * time, or the DVB and V4L analog API at the same time, since many
+ * only have one converter that can be in either analog or digital
+ * mode. Accessing and/or changing mode of a converter while it is
+ * in use by another function results in video stream error.
+ *
+ * A shared devres that can be locked and unlocked by various drivers
+ * that control media functions on a single media device is needed to
+ * address the above problems.
+ *
+ * A token devres that can be looked up by a token for locking, try
+ * locking, unlocking will help avoid adding data structure
+ * dependencies between various media drivers. This token is a unique
+ * string that can be constructed from a common data structure such as
+ * struct device, bus_name, and hardware address.
+ *
+ * The devm_token_* interfaces manage access to token resource.
+ *
+ * Interfaces:
+ * devm_token_create()
+ * devm_token_destroy()
+ * devm_token_lock()
+ * devm_token_unlock()
+ * Usage:
+ * Create token:
+ * Call devm_token_create() with a token id which is
+ * a unique string.
+ * Lock token:
+ * Call devm_token_lock() to lock or try lock a token.
+ * Unlock token:
+ * Call devm_token_unlock().
+ * Destroy token:
+ * Call devm_token_destroy() to delete the token.
+ *
+*/
+#include <linux/device.h>
+#include <linux/token_devres.h>
+
+struct token_devres {
+ struct mutex lock;
+ bool in_use;
+ char id[];
+};
+
+static int devm_token_match(struct device *dev, void *res, void *data)
+{
+ struct token_devres *tkn = res;
+
+ /* compare the token data and return 1 if it matches */
+ return !strcmp(tkn->id, data);
+}
+
+static void devm_token_release(struct device *dev, void *res)
+{
+ struct token_devres *tkn = res;
+
+ mutex_destroy(&tkn->lock);
+}
+
+/* creates a token devres and marks it available */
+int devm_token_create(struct device *dev, const char *id)
+{
+ struct token_devres *tkn;
+ size_t tkn_size;
+
+ tkn_size = sizeof(struct token_devres) + strlen(id) + 1;
+ tkn = devres_alloc(devm_token_release, tkn_size, GFP_KERNEL);
+ if (!tkn)
+ return -ENOMEM;
+
+ strcpy(tkn->id, id);
+ tkn->in_use = false;
+ mutex_init(&tkn->lock);
+
+ devres_add(dev, tkn);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(devm_token_create);
+
+/* If token is available, lock it for the caller, If not return -EBUSY */
+int devm_token_lock(struct device *dev, const char *id)
+{
+ struct token_devres *tkn_ptr;
+ int rc = 0;
+
+ tkn_ptr = devres_find(dev, devm_token_release, devm_token_match,
+ (void *)id);
+ if (tkn_ptr == NULL)
+ return -ENODEV;
+
+ if (!mutex_trylock(&tkn_ptr->lock))
+ return -EBUSY;
+
+ if (tkn_ptr->in_use)
+ rc = -EBUSY;
+ else
+ tkn_ptr->in_use = true;
+
+ mutex_unlock(&tkn_ptr->lock);
+ return rc;
+}
+EXPORT_SYMBOL_GPL(devm_token_lock);
+
+/* If token is locked, unlock */
+int devm_token_unlock(struct device *dev, const char *id)
+{
+ struct token_devres *tkn_ptr;
+
+ tkn_ptr = devres_find(dev, devm_token_release, devm_token_match,
+ (void *) id);
+ if (tkn_ptr == NULL)
+ return -ENODEV;
+
+ mutex_lock(&tkn_ptr->lock);
+ tkn_ptr->in_use = false;
+ mutex_unlock(&tkn_ptr->lock);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(devm_token_unlock);
+
+/* destroy an existing token */
+int devm_token_destroy(struct device *dev, const char *id)
+{
+ int rc;
+
+ rc = devres_release(dev, devm_token_release, devm_token_match,
+ (void *) id);
+ WARN_ON(rc);
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(devm_token_destroy);
diff --git a/include/linux/token_devres.h b/include/linux/token_devres.h
new file mode 100644
index 0000000..e411fd5
--- /dev/null
+++ b/include/linux/token_devres.h
@@ -0,0 +1,19 @@
+/*
+ * token_devres.h - managed token resource
+ *
+ * Copyright (c) 2014 Shuah Khan <[email protected]>
+ * Copyright (c) 2014 Samsung Electronics Co., Ltd.
+ *
+ * This file is released under the GPLv2.
+ */
+#ifndef __LINUX_TOKEN_DEVRES_H
+#define __LINUX_TOKEN_DEVRES_H
+
+struct device;
+
+extern int devm_token_create(struct device *dev, const char *id);
+extern int devm_token_lock(struct device *dev, const char *id);
+extern int devm_token_unlock(struct device *dev, const char *id);
+extern int devm_token_destroy(struct device *dev, const char *id);
+
+#endif /* __LINUX_TOKEN_DEVRES_H */
--
1.7.10.4
Changes to em28xx-dvb to initialze dvb fe tuner token when
dvb fe is registered. This will provide dvb fe the em28xx
tuner token devres for sharing tuner across analog and
digital functions.
Signed-off-by: Shuah Khan <[email protected]>
---
drivers/media/usb/em28xx/em28xx-dvb.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/drivers/media/usb/em28xx/em28xx-dvb.c b/drivers/media/usb/em28xx/em28xx-dvb.c
index f599b18..829e7c8 100644
--- a/drivers/media/usb/em28xx/em28xx-dvb.c
+++ b/drivers/media/usb/em28xx/em28xx-dvb.c
@@ -916,6 +916,10 @@ static int em28xx_register_dvb(struct em28xx_dvb *dvb, struct module *module,
dvb->adapter.priv = &dev->i2c_bus[dev->def_i2c_bus];
+ dvb->fe[0]->tuner_tkn = dev->tuner_tkn;
+ if (dvb->fe[1])
+ dvb->fe[1]->tuner_tkn = dev->tuner_tkn;
+
/* register frontend */
result = dvb_register_frontend(&dvb->adapter, dvb->fe[0]);
if (result < 0) {
--
1.7.10.4
Add a new field tuner_tkn to struct dvb_frontend. Drivers can
create tuner token using devm_token_create() and initialize
the tuner_tkn when frontend is registered with the dvb-core.
This change enables drivers to provide a token devres for tuner
access control.
Change dvb_frontend to lock tuner token for exclusive access to
tuner function for digital TV function use. When Tuner token is
present, dvb_frontend_start() calls devm_token_lock() to lock
the token. If token is busy, -EBUSY is returned to the user-space.
Tuner token is unlocked if kdvb adapter fe kthread fails to start.
This token is held in use as long as the kdvb adapter fe kthread
is running. Tuner token is unlocked in dvb_frontend_thread() when
kdvb adapter fe thread exits.
Signed-off-by: Shuah Khan <[email protected]>
---
drivers/media/dvb-core/dvb_frontend.c | 15 +++++++++++++++
drivers/media/dvb-core/dvb_frontend.h | 1 +
2 files changed, 16 insertions(+)
diff --git a/drivers/media/dvb-core/dvb_frontend.c b/drivers/media/dvb-core/dvb_frontend.c
index 6ce435a..2b35e3f 100644
--- a/drivers/media/dvb-core/dvb_frontend.c
+++ b/drivers/media/dvb-core/dvb_frontend.c
@@ -41,6 +41,7 @@
#include <linux/jiffies.h>
#include <linux/kthread.h>
#include <asm/processor.h>
+#include <linux/token_devres.h>
#include "dvb_frontend.h"
#include "dvbdev.h"
@@ -747,6 +748,9 @@ restart:
if (semheld)
up(&fepriv->sem);
dvb_frontend_wakeup(fe);
+
+ if (fe->tuner_tkn)
+ devm_token_unlock(fe->dvb->device, fe->tuner_tkn);
return 0;
}
@@ -840,6 +844,15 @@ static int dvb_frontend_start(struct dvb_frontend *fe)
fepriv->state = FESTATE_IDLE;
fepriv->exit = DVB_FE_NO_EXIT;
fepriv->thread = NULL;
+
+ if (fe->tuner_tkn) {
+ ret = devm_token_lock(fe->dvb->device, fe->tuner_tkn);
+ if (ret) {
+ dev_info(fe->dvb->device, "Tuner is busy %d\n", ret);
+ return ret;
+ }
+ }
+
mb();
fe_thread = kthread_run(dvb_frontend_thread, fe,
@@ -850,6 +863,8 @@ static int dvb_frontend_start(struct dvb_frontend *fe)
"dvb_frontend_start: failed to start kthread (%d)\n",
ret);
up(&fepriv->sem);
+ if (fe->tuner_tkn)
+ devm_token_unlock(fe->dvb->device, fe->tuner_tkn);
return ret;
}
fepriv->thread = fe_thread;
diff --git a/drivers/media/dvb-core/dvb_frontend.h b/drivers/media/dvb-core/dvb_frontend.h
index 371b6ca..c9ba5fd 100644
--- a/drivers/media/dvb-core/dvb_frontend.h
+++ b/drivers/media/dvb-core/dvb_frontend.h
@@ -418,6 +418,7 @@ struct dvb_frontend {
#define DVB_FRONTEND_COMPONENT_DEMOD 1
int (*callback)(void *adapter_priv, int component, int cmd, int arg);
int id;
+ char *tuner_tkn;
};
extern int dvb_register_frontend(struct dvb_adapter *dvb,
--
1.7.10.4
Changes add a new tuner_tkn field to struct em28xx and create
a token devres to allow sharing tuner function across analog
and digital functions. Tuner token is created during probe in
em28xx_usb_probe() and destroyed during disconnect in
em28xx_release_resources().
Signed-off-by: Shuah Khan <[email protected]>
---
drivers/media/usb/em28xx/em28xx-cards.c | 41 +++++++++++++++++++++++++++++++
drivers/media/usb/em28xx/em28xx.h | 4 +++
2 files changed, 45 insertions(+)
diff --git a/drivers/media/usb/em28xx/em28xx-cards.c b/drivers/media/usb/em28xx/em28xx-cards.c
index 50aa5a5..01c1955 100644
--- a/drivers/media/usb/em28xx/em28xx-cards.c
+++ b/drivers/media/usb/em28xx/em28xx-cards.c
@@ -2428,6 +2428,37 @@ static struct em28xx_hash_table em28xx_i2c_hash[] = {
};
/* NOTE: introduce a separate hash table for devices with 16 bit eeproms */
+/* interfaces to create and destroy token resources */
+static int em28xx_create_token_resources(struct em28xx *dev)
+{
+ int rc = 0, len;
+ char buf[64];
+
+ /* create token devres for tuner */
+ len = snprintf(buf, sizeof(buf),
+ "tuner:%s-%s-%d",
+ dev_name(&dev->udev->dev),
+ dev->udev->bus->bus_name,
+ dev->tuner_addr);
+
+ dev->tuner_tkn = devm_kzalloc(&dev->udev->dev, len + 1, GFP_KERNEL);
+ if (!dev->tuner_tkn)
+ return -ENOMEM;
+
+ strcpy(dev->tuner_tkn, buf);
+ rc = devm_token_create(&dev->udev->dev, dev->tuner_tkn);
+ if (rc)
+ return rc;
+
+ em28xx_info("Tuner token created\n");
+ return rc;
+}
+
+static void em28xx_destroy_token_resources(struct em28xx *dev)
+{
+ devm_token_destroy(&dev->udev->dev, dev->tuner_tkn);
+}
+
int em28xx_tuner_callback(void *ptr, int component, int command, int arg)
{
struct em28xx_i2c_bus *i2c_bus = ptr;
@@ -2949,6 +2980,9 @@ static void em28xx_release_resources(struct em28xx *dev)
em28xx_i2c_unregister(dev, 1);
em28xx_i2c_unregister(dev, 0);
+ /* destroy token resources */
+ em28xx_destroy_token_resources(dev);
+
usb_put_dev(dev->udev);
/* Mark device as unused */
@@ -3431,6 +3465,13 @@ static int em28xx_usb_probe(struct usb_interface *interface,
kref_init(&dev->ref);
+ /* create token resources before requesting for modules */
+ if (em28xx_create_token_resources(dev)) {
+ em28xx_errdev("Error creating token resources!\n");
+ retval = -ENOMEM;
+ goto err_free;
+ }
+
request_modules(dev);
/* Should be the last thing to do, to avoid newer udev's to
diff --git a/drivers/media/usb/em28xx/em28xx.h b/drivers/media/usb/em28xx/em28xx.h
index 2051fc9..e82f868 100644
--- a/drivers/media/usb/em28xx/em28xx.h
+++ b/drivers/media/usb/em28xx/em28xx.h
@@ -34,6 +34,7 @@
#include <linux/mutex.h>
#include <linux/kref.h>
#include <linux/videodev2.h>
+#include <linux/token_devres.h>
#include <media/videobuf2-vmalloc.h>
#include <media/v4l2-device.h>
@@ -547,6 +548,9 @@ struct em28xx {
int devno; /* marks the number of this device */
enum em28xx_chip_id chip_id;
+ /* token resources */
+ char *tuner_tkn; /* tuner token id */
+
unsigned int is_em25xx:1; /* em25xx/em276x/7x/8x family bridge */
unsigned char disconnected:1; /* device has been diconnected */
unsigned int has_video:1;
--
1.7.10.4