This patch introduces a character device interface for the Counter
subsystem. Device data is exposed through standard character device read
operations. Device data is gathered when a Counter event is pushed by
the respective Counter device driver. Configuration is handled via ioctl
operations on the respective Counter character device node.
Cc: David Lechner <[email protected]>
Cc: Gwendal Grignou <[email protected]>
Cc: Dan Carpenter <[email protected]>
Cc: Oleksij Rempel <[email protected]>
Signed-off-by: William Breathitt Gray <[email protected]>
---
drivers/counter/Makefile | 2 +-
drivers/counter/counter-chrdev.c | 578 +++++++++++++++++++++++++++++++
drivers/counter/counter-chrdev.h | 14 +
drivers/counter/counter-core.c | 56 ++-
include/linux/counter.h | 56 +++
include/uapi/linux/counter.h | 98 ++++++
6 files changed, 798 insertions(+), 6 deletions(-)
create mode 100644 drivers/counter/counter-chrdev.c
create mode 100644 drivers/counter/counter-chrdev.h
diff --git a/drivers/counter/Makefile b/drivers/counter/Makefile
index 1ab7e087fdc2..8fde6c100ebc 100644
--- a/drivers/counter/Makefile
+++ b/drivers/counter/Makefile
@@ -4,7 +4,7 @@
#
obj-$(CONFIG_COUNTER) += counter.o
-counter-y := counter-core.o counter-sysfs.o
+counter-y := counter-core.o counter-sysfs.o counter-chrdev.o
obj-$(CONFIG_104_QUAD_8) += 104-quad-8.o
obj-$(CONFIG_INTERRUPT_CNT) += interrupt-cnt.o
diff --git a/drivers/counter/counter-chrdev.c b/drivers/counter/counter-chrdev.c
new file mode 100644
index 000000000000..967c94ae95bb
--- /dev/null
+++ b/drivers/counter/counter-chrdev.c
@@ -0,0 +1,578 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Generic Counter character device interface
+ * Copyright (C) 2020 William Breathitt Gray
+ */
+#include <linux/atomic.h>
+#include <linux/cdev.h>
+#include <linux/counter.h>
+#include <linux/err.h>
+#include <linux/errno.h>
+#include <linux/export.h>
+#include <linux/fs.h>
+#include <linux/kfifo.h>
+#include <linux/list.h>
+#include <linux/mutex.h>
+#include <linux/nospec.h>
+#include <linux/poll.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/timekeeping.h>
+#include <linux/types.h>
+#include <linux/uaccess.h>
+#include <linux/wait.h>
+
+#include "counter-chrdev.h"
+
+struct counter_comp_node {
+ struct list_head l;
+ struct counter_component component;
+ struct counter_comp comp;
+ void *parent;
+};
+
+#define counter_comp_read_is_equal(a, b) \
+ (a.action_read == b.action_read || \
+ a.device_u8_read == b.device_u8_read || \
+ a.count_u8_read == b.count_u8_read || \
+ a.signal_u8_read == b.signal_u8_read || \
+ a.device_u32_read == b.device_u32_read || \
+ a.count_u32_read == b.count_u32_read || \
+ a.signal_u32_read == b.signal_u32_read || \
+ a.device_u64_read == b.device_u64_read || \
+ a.count_u64_read == b.count_u64_read || \
+ a.signal_u64_read == b.signal_u64_read)
+
+#define counter_comp_read_is_set(comp) \
+ (comp.action_read || \
+ comp.device_u8_read || \
+ comp.count_u8_read || \
+ comp.signal_u8_read || \
+ comp.device_u32_read || \
+ comp.count_u32_read || \
+ comp.signal_u32_read || \
+ comp.device_u64_read || \
+ comp.count_u64_read || \
+ comp.signal_u64_read)
+
+static ssize_t counter_chrdev_read(struct file *filp, char __user *buf,
+ size_t len, loff_t *f_ps)
+{
+ struct counter_device *const counter = filp->private_data;
+ int err;
+ unsigned int copied;
+
+ if (!counter->ops)
+ return -ENODEV;
+
+ if (len < sizeof(struct counter_event))
+ return -EINVAL;
+
+ do {
+ if (kfifo_is_empty(&counter->events)) {
+ if (filp->f_flags & O_NONBLOCK)
+ return -EAGAIN;
+
+ err = wait_event_interruptible(counter->events_wait,
+ !kfifo_is_empty(&counter->events) ||
+ !counter->ops);
+ if (err < 0)
+ return err;
+ if (!counter->ops)
+ return -ENODEV;
+ }
+
+ if (mutex_lock_interruptible(&counter->events_lock))
+ return -ERESTARTSYS;
+ err = kfifo_to_user(&counter->events, buf, len, &copied);
+ mutex_unlock(&counter->events_lock);
+ if (err < 0)
+ return err;
+ } while (!copied);
+
+ return copied;
+}
+
+static __poll_t counter_chrdev_poll(struct file *filp,
+ struct poll_table_struct *pollt)
+{
+ struct counter_device *const counter = filp->private_data;
+ __poll_t events = 0;
+
+ if (!counter->ops)
+ return events;
+
+ poll_wait(filp, &counter->events_wait, pollt);
+
+ if (!kfifo_is_empty(&counter->events))
+ events = EPOLLIN | EPOLLRDNORM;
+
+ return events;
+}
+
+static void counter_events_list_free(struct list_head *const events_list)
+{
+ struct counter_event_node *p, *n;
+ struct counter_comp_node *q, *o;
+
+ list_for_each_entry_safe(p, n, events_list, l) {
+ /* Free associated component nodes */
+ list_for_each_entry_safe(q, o, &p->comp_list, l) {
+ list_del(&q->l);
+ kfree(q);
+ }
+
+ /* Free event node */
+ list_del(&p->l);
+ kfree(p);
+ }
+}
+
+static int counter_set_event_node(struct counter_device *const counter,
+ struct counter_watch *const watch,
+ const struct counter_comp_node *const cfg)
+{
+ struct counter_event_node *event_node;
+ int err = 0;
+ struct counter_comp_node *comp_node;
+
+ /* Search for event in the list */
+ list_for_each_entry(event_node, &counter->next_events_list, l)
+ if (event_node->event == watch->event &&
+ event_node->channel == watch->channel)
+ break;
+
+ /* If event is not already in the list */
+ if (&event_node->l == &counter->next_events_list) {
+ /* Allocate new event node */
+ event_node = kmalloc(sizeof(*event_node), GFP_KERNEL);
+ if (!event_node)
+ return -ENOMEM;
+
+ /* Configure event node and add to the list */
+ event_node->event = watch->event;
+ event_node->channel = watch->channel;
+ INIT_LIST_HEAD(&event_node->comp_list);
+ list_add(&event_node->l, &counter->next_events_list);
+ }
+
+ /* Check if component watch has already been set before */
+ list_for_each_entry(comp_node, &event_node->comp_list, l)
+ if (comp_node->parent == cfg->parent &&
+ counter_comp_read_is_equal(comp_node->comp, cfg->comp)) {
+ err = -EINVAL;
+ goto exit_free_event_node;
+ }
+
+ /* Allocate component node */
+ comp_node = kmalloc(sizeof(*comp_node), GFP_KERNEL);
+ if (!comp_node) {
+ err = -ENOMEM;
+ goto exit_free_event_node;
+ }
+ *comp_node = *cfg;
+
+ /* Add component node to event node */
+ list_add_tail(&comp_node->l, &event_node->comp_list);
+
+exit_free_event_node:
+ /* Free event node if no one else is watching */
+ if (list_empty(&event_node->comp_list)) {
+ list_del(&event_node->l);
+ kfree(event_node);
+ }
+
+ return err;
+}
+
+static int counter_enable_events(struct counter_device *const counter)
+{
+ unsigned long flags;
+ int err = 0;
+
+ mutex_lock(&counter->n_events_list_lock);
+ spin_lock_irqsave(&counter->events_list_lock, flags);
+
+ counter_events_list_free(&counter->events_list);
+ list_replace_init(&counter->next_events_list,
+ &counter->events_list);
+
+ if (counter->ops->events_configure)
+ err = counter->ops->events_configure(counter);
+
+ spin_unlock_irqrestore(&counter->events_list_lock, flags);
+ mutex_unlock(&counter->n_events_list_lock);
+
+ return err;
+}
+
+static int counter_disable_events(struct counter_device *const counter)
+{
+ unsigned long flags;
+ int err = 0;
+
+ spin_lock_irqsave(&counter->events_list_lock, flags);
+
+ counter_events_list_free(&counter->events_list);
+
+ if (counter->ops->events_configure)
+ err = counter->ops->events_configure(counter);
+
+ spin_unlock_irqrestore(&counter->events_list_lock, flags);
+
+ mutex_lock(&counter->n_events_list_lock);
+
+ counter_events_list_free(&counter->next_events_list);
+
+ mutex_unlock(&counter->n_events_list_lock);
+
+ return err;
+}
+
+static int counter_add_watch(struct counter_device *const counter,
+ const unsigned long arg)
+{
+ void __user *const uwatch = (void __user *)arg;
+ struct counter_watch watch;
+ struct counter_comp_node comp_node = {};
+ size_t parent, id;
+ struct counter_comp *ext;
+ size_t num_ext;
+ int err = 0;
+
+ if (copy_from_user(&watch, uwatch, sizeof(watch)))
+ return -EFAULT;
+
+ if (watch.component.type == COUNTER_COMPONENT_NONE)
+ goto no_component;
+
+ parent = watch.component.parent;
+
+ /* Configure parent component info for comp node */
+ switch (watch.component.scope) {
+ case COUNTER_SCOPE_DEVICE:
+ ext = counter->ext;
+ num_ext = counter->num_ext;
+ break;
+ case COUNTER_SCOPE_SIGNAL:
+ if (parent >= counter->num_signals)
+ return -EINVAL;
+ parent = array_index_nospec(parent, counter->num_signals);
+
+ comp_node.parent = counter->signals + parent;
+
+ ext = counter->signals[parent].ext;
+ num_ext = counter->signals[parent].num_ext;
+ break;
+ case COUNTER_SCOPE_COUNT:
+ if (parent >= counter->num_counts)
+ return -EINVAL;
+ parent = array_index_nospec(parent, counter->num_counts);
+
+ comp_node.parent = counter->counts + parent;
+
+ ext = counter->counts[parent].ext;
+ num_ext = counter->counts[parent].num_ext;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ id = watch.component.id;
+
+ /* Configure component info for comp node */
+ switch (watch.component.type) {
+ case COUNTER_COMPONENT_SIGNAL:
+ if (watch.component.scope != COUNTER_SCOPE_SIGNAL)
+ return -EINVAL;
+
+ comp_node.comp.type = COUNTER_COMP_SIGNAL_LEVEL;
+ comp_node.comp.signal_u32_read = counter->ops->signal_read;
+ break;
+ case COUNTER_COMPONENT_COUNT:
+ if (watch.component.scope != COUNTER_SCOPE_COUNT)
+ return -EINVAL;
+
+ comp_node.comp.type = COUNTER_COMP_U64;
+ comp_node.comp.count_u64_read = counter->ops->count_read;
+ break;
+ case COUNTER_COMPONENT_FUNCTION:
+ if (watch.component.scope != COUNTER_SCOPE_COUNT)
+ return -EINVAL;
+
+ comp_node.comp.type = COUNTER_COMP_FUNCTION;
+ comp_node.comp.count_u32_read = counter->ops->function_read;
+ break;
+ case COUNTER_COMPONENT_SYNAPSE_ACTION:
+ if (watch.component.scope != COUNTER_SCOPE_COUNT)
+ return -EINVAL;
+ if (id >= counter->counts[parent].num_synapses)
+ return -EINVAL;
+ id = array_index_nospec(id, counter->counts[parent].num_synapses);
+
+ comp_node.comp.type = COUNTER_COMP_SYNAPSE_ACTION;
+ comp_node.comp.action_read = counter->ops->action_read;
+ comp_node.comp.priv = counter->counts[parent].synapses + id;
+ break;
+ case COUNTER_COMPONENT_EXTENSION:
+ if (id >= num_ext)
+ return -EINVAL;
+ id = array_index_nospec(id, num_ext);
+
+ comp_node.comp = ext[id];
+ break;
+ default:
+ return -EINVAL;
+ }
+ if (!counter_comp_read_is_set(comp_node.comp))
+ return -EOPNOTSUPP;
+
+no_component:
+ mutex_lock(&counter->n_events_list_lock);
+
+ if (counter->ops->watch_validate) {
+ err = counter->ops->watch_validate(counter, &watch);
+ if (err < 0)
+ goto err_exit;
+ }
+
+ comp_node.component = watch.component;
+
+ err = counter_set_event_node(counter, &watch, &comp_node);
+
+err_exit:
+ mutex_unlock(&counter->n_events_list_lock);
+
+ return err;
+}
+
+static long counter_chrdev_ioctl(struct file *filp, unsigned int cmd,
+ unsigned long arg)
+{
+ struct counter_device *const counter = filp->private_data;
+ int ret = -ENODEV;
+
+ mutex_lock(&counter->ops_exist_lock);
+
+ if (!counter->ops)
+ goto out_unlock;
+
+ switch (cmd) {
+ case COUNTER_ADD_WATCH_IOCTL:
+ ret = counter_add_watch(counter, arg);
+ break;
+ case COUNTER_ENABLE_EVENTS_IOCTL:
+ ret = counter_enable_events(counter);
+ break;
+ case COUNTER_DISABLE_EVENTS_IOCTL:
+ ret = counter_disable_events(counter);
+ break;
+ default:
+ ret = -ENOIOCTLCMD;
+ break;
+ }
+
+out_unlock:
+ mutex_unlock(&counter->ops_exist_lock);
+
+ return ret;
+}
+
+static int counter_chrdev_open(struct inode *inode, struct file *filp)
+{
+ struct counter_device *const counter = container_of(inode->i_cdev,
+ typeof(*counter),
+ chrdev);
+
+ /* Ensure chrdev is not opened more than 1 at a time */
+ if (!atomic_add_unless(&counter->chrdev_lock, 1, 1))
+ return -EBUSY;
+
+ get_device(&counter->dev);
+ filp->private_data = counter;
+
+ return nonseekable_open(inode, filp);
+}
+
+static int counter_chrdev_release(struct inode *inode, struct file *filp)
+{
+ struct counter_device *const counter = filp->private_data;
+ int ret = 0;
+
+ mutex_lock(&counter->ops_exist_lock);
+
+ if (!counter->ops) {
+ /* Free any lingering held memory */
+ counter_events_list_free(&counter->events_list);
+ counter_events_list_free(&counter->next_events_list);
+ ret = -ENODEV;
+ goto out_unlock;
+ }
+
+ ret = counter_disable_events(counter);
+ if (ret < 0) {
+ mutex_unlock(&counter->ops_exist_lock);
+ return ret;
+ }
+
+out_unlock:
+ mutex_unlock(&counter->ops_exist_lock);
+
+ put_device(&counter->dev);
+ atomic_dec(&counter->chrdev_lock);
+
+ return ret;
+}
+
+static const struct file_operations counter_fops = {
+ .owner = THIS_MODULE,
+ .llseek = no_llseek,
+ .read = counter_chrdev_read,
+ .poll = counter_chrdev_poll,
+ .unlocked_ioctl = counter_chrdev_ioctl,
+ .open = counter_chrdev_open,
+ .release = counter_chrdev_release,
+};
+
+int counter_chrdev_add(struct counter_device *const counter)
+{
+ /* Initialize Counter events lists */
+ INIT_LIST_HEAD(&counter->events_list);
+ INIT_LIST_HEAD(&counter->next_events_list);
+ spin_lock_init(&counter->events_list_lock);
+ mutex_init(&counter->n_events_list_lock);
+ init_waitqueue_head(&counter->events_wait);
+ mutex_init(&counter->events_lock);
+
+ /* Initialize character device */
+ atomic_set(&counter->chrdev_lock, 0);
+ cdev_init(&counter->chrdev, &counter_fops);
+
+ /* Allocate Counter events queue */
+ return kfifo_alloc(&counter->events, 64, GFP_KERNEL);
+}
+
+void counter_chrdev_remove(struct counter_device *const counter)
+{
+ kfifo_free(&counter->events);
+}
+
+static int counter_get_data(struct counter_device *const counter,
+ const struct counter_comp_node *const comp_node,
+ u64 *const value)
+{
+ const struct counter_comp *const comp = &comp_node->comp;
+ void *const parent = comp_node->parent;
+ u8 value_u8 = 0;
+ u32 value_u32 = 0;
+ int ret;
+
+ if (comp_node->component.type == COUNTER_COMPONENT_NONE)
+ return 0;
+
+ switch (comp->type) {
+ case COUNTER_COMP_U8:
+ case COUNTER_COMP_BOOL:
+ switch (comp_node->component.scope) {
+ case COUNTER_SCOPE_DEVICE:
+ ret = comp->device_u8_read(counter, &value_u8);
+ break;
+ case COUNTER_SCOPE_SIGNAL:
+ ret = comp->signal_u8_read(counter, parent, &value_u8);
+ break;
+ case COUNTER_SCOPE_COUNT:
+ ret = comp->count_u8_read(counter, parent, &value_u8);
+ break;
+ }
+ *value = value_u8;
+ return ret;
+ case COUNTER_COMP_SIGNAL_LEVEL:
+ case COUNTER_COMP_FUNCTION:
+ case COUNTER_COMP_ENUM:
+ case COUNTER_COMP_COUNT_DIRECTION:
+ case COUNTER_COMP_COUNT_MODE:
+ switch (comp_node->component.scope) {
+ case COUNTER_SCOPE_DEVICE:
+ ret = comp->device_u32_read(counter, &value_u32);
+ break;
+ case COUNTER_SCOPE_SIGNAL:
+ ret = comp->signal_u32_read(counter, parent,
+ &value_u32);
+ break;
+ case COUNTER_SCOPE_COUNT:
+ ret = comp->count_u32_read(counter, parent, &value_u32);
+ break;
+ }
+ *value = value_u32;
+ return ret;
+ case COUNTER_COMP_U64:
+ switch (comp_node->component.scope) {
+ case COUNTER_SCOPE_DEVICE:
+ return comp->device_u64_read(counter, value);
+ case COUNTER_SCOPE_SIGNAL:
+ return comp->signal_u64_read(counter, parent, value);
+ case COUNTER_SCOPE_COUNT:
+ return comp->count_u64_read(counter, parent, value);
+ default:
+ return -EINVAL;
+ }
+ case COUNTER_COMP_SYNAPSE_ACTION:
+ ret = comp->action_read(counter, parent, comp->priv,
+ &value_u32);
+ *value = value_u32;
+ return ret;
+ default:
+ return -EINVAL;
+ }
+}
+
+/**
+ * counter_push_event - queue event for userspace reading
+ * @counter: pointer to Counter structure
+ * @event: triggered event
+ * @channel: event channel
+ *
+ * Note: If no one is watching for the respective event, it is silently
+ * discarded.
+ */
+void counter_push_event(struct counter_device *const counter, const u8 event,
+ const u8 channel)
+{
+ struct counter_event ev;
+ unsigned int copied = 0;
+ unsigned long flags;
+ struct counter_event_node *event_node;
+ struct counter_comp_node *comp_node;
+
+ ev.timestamp = ktime_get_ns();
+ ev.watch.event = event;
+ ev.watch.channel = channel;
+
+ /* Could be in an interrupt context, so use a spin lock */
+ spin_lock_irqsave(&counter->events_list_lock, flags);
+
+ /* Search for event in the list */
+ list_for_each_entry(event_node, &counter->events_list, l)
+ if (event_node->event == event &&
+ event_node->channel == channel)
+ break;
+
+ /* If event is not in the list */
+ if (&event_node->l == &counter->events_list)
+ goto exit_early;
+
+ /* Read and queue relevant comp for userspace */
+ list_for_each_entry(comp_node, &event_node->comp_list, l) {
+ ev.watch.component = comp_node->component;
+ ev.status = -counter_get_data(counter, comp_node, &ev.value);
+
+ copied += kfifo_in(&counter->events, &ev, 1);
+ }
+
+exit_early:
+ spin_unlock_irqrestore(&counter->events_list_lock, flags);
+
+ if (copied)
+ wake_up_poll(&counter->events_wait, EPOLLIN);
+}
+EXPORT_SYMBOL_GPL(counter_push_event);
diff --git a/drivers/counter/counter-chrdev.h b/drivers/counter/counter-chrdev.h
new file mode 100644
index 000000000000..5529d16703c4
--- /dev/null
+++ b/drivers/counter/counter-chrdev.h
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Counter character device interface
+ * Copyright (C) 2020 William Breathitt Gray
+ */
+#ifndef _COUNTER_CHRDEV_H_
+#define _COUNTER_CHRDEV_H_
+
+#include <linux/counter.h>
+
+int counter_chrdev_add(struct counter_device *const counter);
+void counter_chrdev_remove(struct counter_device *const counter);
+
+#endif /* _COUNTER_CHRDEV_H_ */
diff --git a/drivers/counter/counter-core.c b/drivers/counter/counter-core.c
index 3cda2c47bacb..5acc54539623 100644
--- a/drivers/counter/counter-core.c
+++ b/drivers/counter/counter-core.c
@@ -3,14 +3,22 @@
* Generic Counter interface
* Copyright (C) 2020 William Breathitt Gray
*/
+#include <linux/cdev.h>
#include <linux/counter.h>
#include <linux/device.h>
+#include <linux/device/bus.h>
#include <linux/export.h>
+#include <linux/fs.h>
#include <linux/gfp.h>
#include <linux/idr.h>
#include <linux/init.h>
+#include <linux/kdev_t.h>
#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/types.h>
+#include <linux/wait.h>
+#include "counter-chrdev.h"
#include "counter-sysfs.h"
/* Provides a unique ID for each counter device */
@@ -18,6 +26,9 @@ static DEFINE_IDA(counter_ida);
static void counter_device_release(struct device *dev)
{
+ struct counter_device *const counter = dev_get_drvdata(dev);
+
+ counter_chrdev_remove(counter);
ida_free(&counter_ida, dev->id);
}
@@ -31,6 +42,8 @@ static struct bus_type counter_bus_type = {
.dev_name = "counter",
};
+static dev_t counter_devt;
+
/**
* counter_register - register Counter to the system
* @counter: pointer to Counter to register
@@ -53,10 +66,13 @@ int counter_register(struct counter_device *const counter)
if (id < 0)
return id;
+ mutex_init(&counter->ops_exist_lock);
+
/* Configure device structure for Counter */
dev->id = id;
dev->type = &counter_device_type;
dev->bus = &counter_bus_type;
+ dev->devt = MKDEV(MAJOR(counter_devt), id);
if (counter->parent) {
dev->parent = counter->parent;
dev->of_node = counter->parent->of_node;
@@ -64,18 +80,22 @@ int counter_register(struct counter_device *const counter)
device_initialize(dev);
dev_set_drvdata(dev, counter);
- /* Add Counter sysfs attributes */
err = counter_sysfs_add(counter);
if (err < 0)
goto err_free_id;
- /* Add device to system */
- err = device_add(dev);
+ err = counter_chrdev_add(counter);
if (err < 0)
goto err_free_id;
+ err = cdev_device_add(&counter->chrdev, dev);
+ if (err < 0)
+ goto err_remove_chrdev;
+
return 0;
+err_remove_chrdev:
+ counter_chrdev_remove(counter);
err_free_id:
put_device(dev);
return err;
@@ -93,7 +113,16 @@ void counter_unregister(struct counter_device *const counter)
if (!counter)
return;
- device_unregister(&counter->dev);
+ cdev_device_del(&counter->chrdev, &counter->dev);
+
+ mutex_lock(&counter->ops_exist_lock);
+
+ counter->ops = NULL;
+ wake_up(&counter->events_wait);
+
+ mutex_unlock(&counter->ops_exist_lock);
+
+ put_device(&counter->dev);
}
EXPORT_SYMBOL_GPL(counter_unregister);
@@ -127,13 +156,30 @@ int devm_counter_register(struct device *dev,
}
EXPORT_SYMBOL_GPL(devm_counter_register);
+#define COUNTER_DEV_MAX 256
+
static int __init counter_init(void)
{
- return bus_register(&counter_bus_type);
+ int err;
+
+ err = bus_register(&counter_bus_type);
+ if (err < 0)
+ return err;
+
+ err = alloc_chrdev_region(&counter_devt, 0, COUNTER_DEV_MAX, "counter");
+ if (err < 0)
+ goto err_unregister_bus;
+
+ return 0;
+
+err_unregister_bus:
+ bus_unregister(&counter_bus_type);
+ return err;
}
static void __exit counter_exit(void)
{
+ unregister_chrdev_region(counter_devt, COUNTER_DEV_MAX);
bus_unregister(&counter_bus_type);
}
diff --git a/include/linux/counter.h b/include/linux/counter.h
index 7c9f7e23953a..22b14a552b1d 100644
--- a/include/linux/counter.h
+++ b/include/linux/counter.h
@@ -6,9 +6,14 @@
#ifndef _COUNTER_H_
#define _COUNTER_H_
+#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/kernel.h>
+#include <linux/kfifo.h>
+#include <linux/mutex.h>
+#include <linux/spinlock_types.h>
#include <linux/types.h>
+#include <linux/wait.h>
#include <uapi/linux/counter.h>
struct counter_device;
@@ -199,6 +204,20 @@ struct counter_count {
size_t num_ext;
};
+/**
+ * struct counter_event_node - Counter Event node
+ * @l: list of current watching Counter events
+ * @event: event that triggers
+ * @channel: event channel
+ * @comp_list: list of components to watch when event triggers
+ */
+struct counter_event_node {
+ struct list_head l;
+ u8 event;
+ u8 channel;
+ struct list_head comp_list;
+};
+
/**
* struct counter_ops - Callbacks from driver
* @signal_read: optional read callback for Signals. The read level of
@@ -222,6 +241,13 @@ struct counter_count {
* @action_write: optional write callback for Synapse action modes. The
* action mode to write for the respective Synapse is
* passed in via the action parameter.
+ * @events_configure: optional write callback to configure events. The list of
+ * struct counter_event_node may be accessed via the
+ * events_list member of the counter parameter.
+ * @watch_validate: optional callback to validate a watch. The Counter
+ * component watch configuration is passed in via the watch
+ * parameter. A return value of 0 indicates a valid Counter
+ * component watch configuration.
*/
struct counter_ops {
int (*signal_read)(struct counter_device *counter,
@@ -245,6 +271,9 @@ struct counter_ops {
struct counter_count *count,
struct counter_synapse *synapse,
enum counter_synapse_action action);
+ int (*events_configure)(struct counter_device *counter);
+ int (*watch_validate)(struct counter_device *counter,
+ const struct counter_watch *watch);
};
/**
@@ -260,6 +289,16 @@ struct counter_ops {
* @num_ext: number of Counter device extensions specified in @ext
* @priv: optional private data supplied by driver
* @dev: internal device structure
+ * @chrdev: internal character device structure
+ * @events_list: list of current watching Counter events
+ * @events_list_lock: lock to protect Counter events list operations
+ * @next_events_list: list of next watching Counter events
+ * @n_events_list_lock: lock to protect Counter next events list operations
+ * @events: queue of detected Counter events
+ * @events_wait: wait queue to allow blocking reads of Counter events
+ * @events_lock: lock to protect Counter events queue read operations
+ * @chrdev_lock: lock to limit chrdev to a single open at a time
+ * @ops_exist_lock: lock to prevent use during removal
*/
struct counter_device {
const char *name;
@@ -278,12 +317,29 @@ struct counter_device {
void *priv;
struct device dev;
+ struct cdev chrdev;
+ struct list_head events_list;
+ spinlock_t events_list_lock;
+ struct list_head next_events_list;
+ struct mutex n_events_list_lock;
+ DECLARE_KFIFO_PTR(events, struct counter_event);
+ wait_queue_head_t events_wait;
+ struct mutex events_lock;
+ /*
+ * chrdev_lock is locked by counter_chrdev_open() and unlocked by
+ * counter_chrdev_release(), so a mutex is not possible here because
+ * chrdev_lock will invariably be held when returning to user space
+ */
+ atomic_t chrdev_lock;
+ struct mutex ops_exist_lock;
};
int counter_register(struct counter_device *const counter);
void counter_unregister(struct counter_device *const counter);
int devm_counter_register(struct device *dev,
struct counter_device *const counter);
+void counter_push_event(struct counter_device *const counter, const u8 event,
+ const u8 channel);
#define COUNTER_COMP_DEVICE_U8(_name, _read, _write) \
{ \
diff --git a/include/uapi/linux/counter.h b/include/uapi/linux/counter.h
index 6113938a6044..d0aa95aeff7b 100644
--- a/include/uapi/linux/counter.h
+++ b/include/uapi/linux/counter.h
@@ -6,6 +6,19 @@
#ifndef _UAPI_COUNTER_H_
#define _UAPI_COUNTER_H_
+#include <linux/ioctl.h>
+#include <linux/types.h>
+
+/* Component type definitions */
+enum counter_component_type {
+ COUNTER_COMPONENT_NONE,
+ COUNTER_COMPONENT_SIGNAL,
+ COUNTER_COMPONENT_COUNT,
+ COUNTER_COMPONENT_FUNCTION,
+ COUNTER_COMPONENT_SYNAPSE_ACTION,
+ COUNTER_COMPONENT_EXTENSION,
+};
+
/* Component scope definitions */
enum counter_scope {
COUNTER_SCOPE_DEVICE,
@@ -13,6 +26,91 @@ enum counter_scope {
COUNTER_SCOPE_COUNT,
};
+/**
+ * struct counter_component - Counter component identification
+ * @type: component type (one of enum counter_component_type)
+ * @scope: component scope (one of enum counter_scope)
+ * @parent: parent ID (matching the ID suffix of the respective parent sysfs
+ * path as described by the ABI documentation file
+ * Documentation/ABI/testing/sysfs-bus-counter)
+ * @id: component ID (matching the ID provided by the respective *_component_id
+ * sysfs attribute of the desired component)
+ *
+ * For example, if the Count 2 ceiling extension of Counter device 4 is desired,
+ * set type equal to COUNTER_COMPONENT_EXTENSION, scope equal to
+ * COUNTER_COUNT_SCOPE, parent equal to 2, and id equal to the value provided by
+ * the respective /sys/bus/counter/devices/counter4/count2/ceiling_component_id
+ * sysfs attribute.
+ */
+struct counter_component {
+ __u8 type;
+ __u8 scope;
+ __u8 parent;
+ __u8 id;
+};
+
+/* Event type definitions */
+enum counter_event_type {
+ /* Count value increased past ceiling */
+ COUNTER_EVENT_OVERFLOW,
+ /* Count value decreased past floor */
+ COUNTER_EVENT_UNDERFLOW,
+ /* Count value increased past ceiling, or decreased past floor */
+ COUNTER_EVENT_OVERFLOW_UNDERFLOW,
+ /* Count value reached threshold */
+ COUNTER_EVENT_THRESHOLD,
+ /* Index signal detected */
+ COUNTER_EVENT_INDEX,
+};
+
+/**
+ * struct counter_watch - Counter component watch configuration
+ * @component: component to watch when event triggers
+ * @event: event that triggers (one of enum counter_event_type)
+ * @channel: event channel (typically 0 unless the device supports concurrent
+ * events of the same type)
+ */
+struct counter_watch {
+ struct counter_component component;
+ __u8 event;
+ __u8 channel;
+};
+
+/*
+ * Queues a Counter watch for the specified event.
+ *
+ * The queued watches will not be applied until COUNTER_ENABLE_EVENTS_IOCTL is
+ * called.
+ */
+#define COUNTER_ADD_WATCH_IOCTL _IOW(0x3E, 0x00, struct counter_watch)
+/*
+ * Enables monitoring the events specified by the Counter watches that were
+ * queued by COUNTER_ADD_WATCH_IOCTL.
+ *
+ * If events are already enabled, the new set of watches replaces the old one.
+ * Calling this ioctl also has the effect of clearing the queue of watches added
+ * by COUNTER_ADD_WATCH_IOCTL.
+ */
+#define COUNTER_ENABLE_EVENTS_IOCTL _IO(0x3E, 0x01)
+/*
+ * Stops monitoring the previously enabled events.
+ */
+#define COUNTER_DISABLE_EVENTS_IOCTL _IO(0x3E, 0x02)
+
+/**
+ * struct counter_event - Counter event data
+ * @timestamp: best estimate of time of event occurrence, in nanoseconds
+ * @value: component value
+ * @watch: component watch configuration
+ * @status: return status (system error number)
+ */
+struct counter_event {
+ __aligned_u64 timestamp;
+ __aligned_u64 value;
+ struct counter_watch watch;
+ __u8 status;
+};
+
/* Count direction values */
enum counter_count_direction {
COUNTER_COUNT_DIRECTION_FORWARD,
--
2.33.0
Note, review of this now that it has been submitted in a pull request to
me, sorry I missed this previously...
On Wed, Sep 29, 2021 at 12:15:59PM +0900, William Breathitt Gray wrote:
> +static int counter_chrdev_open(struct inode *inode, struct file *filp)
> +{
> + struct counter_device *const counter = container_of(inode->i_cdev,
> + typeof(*counter),
> + chrdev);
> +
> + /* Ensure chrdev is not opened more than 1 at a time */
> + if (!atomic_add_unless(&counter->chrdev_lock, 1, 1))
> + return -EBUSY;
I understand the feeling that you wish to stop userspace from doing
this, but really, it does not work. Eventhough you are doing this
correctly (you should see all the other attempts at doing this), you are
not preventing userspace from having multiple processes access this
device node at the same time, so please, don't even attempt to stop this
from happening.
So you can drop the atomic "lock" you have here, it's not needed at all.
thanks,
greg k-h
On 17/10/2021 15:50:11+0200, Greg KH wrote:
> Note, review of this now that it has been submitted in a pull request to
> me, sorry I missed this previously...
>
> On Wed, Sep 29, 2021 at 12:15:59PM +0900, William Breathitt Gray wrote:
> > +static int counter_chrdev_open(struct inode *inode, struct file *filp)
> > +{
> > + struct counter_device *const counter = container_of(inode->i_cdev,
> > + typeof(*counter),
> > + chrdev);
> > +
> > + /* Ensure chrdev is not opened more than 1 at a time */
> > + if (!atomic_add_unless(&counter->chrdev_lock, 1, 1))
> > + return -EBUSY;
>
> I understand the feeling that you wish to stop userspace from doing
> this, but really, it does not work. Eventhough you are doing this
> correctly (you should see all the other attempts at doing this), you are
> not preventing userspace from having multiple processes access this
> device node at the same time, so please, don't even attempt to stop this
> from happening.
>
> So you can drop the atomic "lock" you have here, it's not needed at all.
>
Could you elaborate a bit here because we've had a similar thing in the
RTC subsystem:
https://elixir.bootlin.com/linux/latest/source/drivers/rtc/dev.c#L28
And it would mean I can remove rtc->flags completely.
--
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
On Sun, Oct 17, 2021 at 04:02:42PM +0200, Alexandre Belloni wrote:
> On 17/10/2021 15:50:11+0200, Greg KH wrote:
> > Note, review of this now that it has been submitted in a pull request to
> > me, sorry I missed this previously...
> >
> > On Wed, Sep 29, 2021 at 12:15:59PM +0900, William Breathitt Gray wrote:
> > > +static int counter_chrdev_open(struct inode *inode, struct file *filp)
> > > +{
> > > + struct counter_device *const counter = container_of(inode->i_cdev,
> > > + typeof(*counter),
> > > + chrdev);
> > > +
> > > + /* Ensure chrdev is not opened more than 1 at a time */
> > > + if (!atomic_add_unless(&counter->chrdev_lock, 1, 1))
> > > + return -EBUSY;
> >
> > I understand the feeling that you wish to stop userspace from doing
> > this, but really, it does not work. Eventhough you are doing this
> > correctly (you should see all the other attempts at doing this), you are
> > not preventing userspace from having multiple processes access this
> > device node at the same time, so please, don't even attempt to stop this
> > from happening.
> >
> > So you can drop the atomic "lock" you have here, it's not needed at all.
> >
>
> Could you elaborate a bit here because we've had a similar thing in the
> RTC subsystem:
>
> https://elixir.bootlin.com/linux/latest/source/drivers/rtc/dev.c#L28
Yeah, that too will not work :( Note, it does stop open from being
called from different processes, but think of the following sequence of
userspace calls:
open()
fork/exec()
both processes access the file descriptor
or passing a fd across a socket?
Or duplicating the file descriptor and sending it to a different task
(like across a socket or many other IPC ways)?
Once userspace has a file descriptor, all bets are off as to where it
goes and what it does with it. There's no need to try to save userspace
from itself by preventing multiple opens when really, it doesn't stop
anyone who really wants to do this.
If userspace does do multiple read/writes from different threads /
processes / whatever on the same file descriptor, it gets to keep the
pieces of the mess it causes. It's not the kernel's job to try to
"protect" userspace from itself here.
Look at serial/tty connections as one example of this always being the
case.
Does that help?
> And it would mean I can remove rtc->flags completely.
I think you can do that.
thanks,
greg k-h
On 17/10/2021 16:40:14+0200, Greg KH wrote:
> On Sun, Oct 17, 2021 at 04:02:42PM +0200, Alexandre Belloni wrote:
> > On 17/10/2021 15:50:11+0200, Greg KH wrote:
> > > Note, review of this now that it has been submitted in a pull request to
> > > me, sorry I missed this previously...
> > >
> > > On Wed, Sep 29, 2021 at 12:15:59PM +0900, William Breathitt Gray wrote:
> > > > +static int counter_chrdev_open(struct inode *inode, struct file *filp)
> > > > +{
> > > > + struct counter_device *const counter = container_of(inode->i_cdev,
> > > > + typeof(*counter),
> > > > + chrdev);
> > > > +
> > > > + /* Ensure chrdev is not opened more than 1 at a time */
> > > > + if (!atomic_add_unless(&counter->chrdev_lock, 1, 1))
> > > > + return -EBUSY;
> > >
> > > I understand the feeling that you wish to stop userspace from doing
> > > this, but really, it does not work. Eventhough you are doing this
> > > correctly (you should see all the other attempts at doing this), you are
> > > not preventing userspace from having multiple processes access this
> > > device node at the same time, so please, don't even attempt to stop this
> > > from happening.
> > >
> > > So you can drop the atomic "lock" you have here, it's not needed at all.
> > >
> >
> > Could you elaborate a bit here because we've had a similar thing in the
> > RTC subsystem:
> >
> > https://elixir.bootlin.com/linux/latest/source/drivers/rtc/dev.c#L28
>
> Yeah, that too will not work :( Note, it does stop open from being
> called from different processes, but think of the following sequence of
> userspace calls:
> open()
> fork/exec()
> both processes access the file descriptor
>
> or passing a fd across a socket?
>
> Or duplicating the file descriptor and sending it to a different task
> (like across a socket or many other IPC ways)?
>
> Once userspace has a file descriptor, all bets are off as to where it
> goes and what it does with it. There's no need to try to save userspace
> from itself by preventing multiple opens when really, it doesn't stop
> anyone who really wants to do this.
>
> If userspace does do multiple read/writes from different threads /
> processes / whatever on the same file descriptor, it gets to keep the
> pieces of the mess it causes. It's not the kernel's job to try to
> "protect" userspace from itself here.
>
> Look at serial/tty connections as one example of this always being the
> case.
>
> Does that help?
>
Thanks for the explanation, this is now clear to me.
> > And it would mean I can remove rtc->flags completely.
>
> I think you can do that.
>
> thanks,
>
> greg k-h
--
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com