The events_queue_size sysfs attribute provides a way for users to
dynamically configure the Counter events queue size for the Counter
character device interface. The size is in number of struct
counter_event data structures. The number of elements will be rounded-up
to a power of 2 due to a requirement of the kfifo_alloc function called
during reallocation of the queue.
Cc: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>
Signed-off-by: William Breathitt Gray <vilhelm.gray@xxxxxxxxx>
---
Documentation/ABI/testing/sysfs-bus-counter | 8 ++++
drivers/counter/counter-chrdev.c | 6 +++
drivers/counter/counter-sysfs.c | 45 +++++++++++++++++++++
include/linux/counter.h | 2 +
4 files changed, 61 insertions(+)
diff --git a/Documentation/ABI/testing/sysfs-bus-counter b/Documentation/ABI/testing/sysfs-bus-counter
index e0e99adb0ecc..84ebb1ed28ed 100644
--- a/Documentation/ABI/testing/sysfs-bus-counter
+++ b/Documentation/ABI/testing/sysfs-bus-counter
@@ -233,6 +233,14 @@ Description:
shorter or equal to configured value are ignored. Value 0 means
filter is disabled.
+What: /sys/bus/counter/devices/counterX/events_queue_size
+KernelVersion: 5.15
+Contact: linux-iio@xxxxxxxxxxxxxxx
+Description:
+ Size of the Counter events queue in number of struct
+ counter_event data structures. The number of elements will be
+ rounded-up to a power of 2.
+
What: /sys/bus/counter/devices/counterX/name
KernelVersion: 5.2
Contact: linux-iio@xxxxxxxxxxxxxxx
diff --git a/drivers/counter/counter-chrdev.c b/drivers/counter/counter-chrdev.c
index d5af82d3c04b..cf94e8f1c4ea 100644
--- a/drivers/counter/counter-chrdev.c
+++ b/drivers/counter/counter-chrdev.c
@@ -3,6 +3,7 @@
* Generic Counter character device interface
* Copyright (C) 2020 William Breathitt Gray
*/
+#include <linux/bitops.h>
#include <linux/cdev.h>
#include <linux/counter.h>
#include <linux/err.h>
@@ -336,6 +337,9 @@ static int counter_chrdev_open(struct inode *inode, struct file *filp)
typeof(*counter),
chrdev);
+ if (test_and_set_bit_lock(0, counter->chrdev_lock))
+ return -EBUSY;
+
get_device(&counter->dev);
filp->private_data = counter;
@@ -352,6 +356,7 @@ static int counter_chrdev_release(struct inode *inode, struct file *filp)
return err;
put_device(&counter->dev);
+ clear_bit_unlock(0, counter->chrdev_lock);
return 0;
}
@@ -376,6 +381,7 @@ int counter_chrdev_add(struct counter_device *const counter)
mutex_init(&counter->events_lock);
/* Initialize character device */
+ clear_bit(0, counter->chrdev_lock);
cdev_init(&counter->chrdev, &counter_fops);
/* Allocate Counter events queue */
diff --git a/drivers/counter/counter-sysfs.c b/drivers/counter/counter-sysfs.c
index df1d75e0d7b8..d2d6495f73c5 100644
--- a/drivers/counter/counter-sysfs.c
+++ b/drivers/counter/counter-sysfs.c
@@ -3,11 +3,13 @@
* Generic Counter sysfs interface
* Copyright (C) 2020 William Breathitt Gray
*/
+#include <linux/bitops.h>
#include <linux/counter.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/gfp.h>
#include <linux/kernel.h>
+#include <linux/kfifo.h>
#include <linux/kstrtox.h>
#include <linux/list.h>
#include <linux/string.h>
@@ -785,12 +787,49 @@ static int counter_num_counts_read(struct counter_device *counter, u8 *val)
return 0;
}
+static int counter_events_queue_size_read(struct counter_device *counter,
+ u64 *val)
+{
+ *val = kfifo_size(&counter->events);
+ return 0;
+}
+
+static int counter_events_queue_size_write(struct counter_device *counter,
+ u64 val)
+{
+ DECLARE_KFIFO_PTR(events, struct counter_event);
+ int err = 0;
+
+ /* Verify chrdev is not currently being used */
+ if (test_and_set_bit_lock(0, counter->chrdev_lock))
+ return -EBUSY;
+
+ /* Allocate new events queue */
+ err = kfifo_alloc(&events, val, GFP_KERNEL);
+ if (err)
+ goto exit_early;
+
+ /* Swap in new events queue */
+ kfifo_free(&counter->events);
+ counter->events.kfifo = events.kfifo;
+
+exit_early:
+ clear_bit_unlock(0, counter->chrdev_lock);
+
+ return err;
+}
+
static struct counter_comp counter_num_signals_comp =
COUNTER_COMP_DEVICE_U8("num_signals", counter_num_signals_read, NULL);
static struct counter_comp counter_num_counts_comp =
COUNTER_COMP_DEVICE_U8("num_counts", counter_num_counts_read, NULL);
+static struct counter_comp counter_events_queue_size_comp =
+ COUNTER_COMP_DEVICE_U64("events_queue_size",
+ counter_events_queue_size_read,
+ counter_events_queue_size_write);
+
static int counter_sysfs_attr_add(struct counter_device *const counter,
struct counter_attribute_group *cattr_group)
{
@@ -829,6 +868,12 @@ static int counter_sysfs_attr_add(struct counter_device *const counter,
if (err < 0)
return err;
+ /* Create events_queue_size attribute */
+ err = counter_attr_create(dev, cattr_group,
+ &counter_events_queue_size_comp, scope, NULL);
+ if (err < 0)
+ return err;
+
/* Create an attribute for each extension */
for (i = 0; i < counter->num_ext; i++) {
ext = &counter->ext[i];
diff --git a/include/linux/counter.h b/include/linux/counter.h
index 895d60a238a9..bfd96fa1f7fe 100644
--- a/include/linux/counter.h
+++ b/include/linux/counter.h
@@ -297,6 +297,7 @@ struct counter_ops {
* @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
*/
struct counter_device {
const char *name;
@@ -323,6 +324,7 @@ struct counter_device {
DECLARE_KFIFO_PTR(events, struct counter_event);
wait_queue_head_t events_wait;
struct mutex events_lock;
+ DECLARE_BITMAP(chrdev_lock, 1);
};
int counter_register(struct counter_device *const counter);
--
2.32.0
