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counter: Implement events_queue_size sysfs attribute

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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@pengutronix.de>
Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Link: https://lore.kernel.org/r/c914b2db2ea0a2637633bcc3e86ded3c94783f2e.1632884256.git.vilhelm.gray@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
This commit is contained in:
William Breathitt Gray 2021-09-29 12:16:04 +09:00 committed by Jonathan Cameron
parent 4bdec61d92
commit feff17a550
2 changed files with 53 additions and 0 deletions
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8
Documentation/ABI/testing/sysfs-bus-counter
View File

@ -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: 5.16
Contact: linux-iio@vger.kernel.org
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@vger.kernel.org

45
drivers/counter/counter-sysfs.c
View File

@ -3,11 +3,13 @@
* Generic Counter sysfs interface
* Copyright (C) 2020 William Breathitt Gray
*/
#include <linux/atomic.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>
@ -783,12 +785,49 @@ 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;
/* Ensure chrdev is not opened more than 1 at a time */
if (!atomic_add_unless(&counter->chrdev_lock, 1, 1))
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:
atomic_dec(&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)
{
@ -827,6 +866,12 @@ 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];