Commit feff17a5 authored by William Breathitt Gray's avatar William Breathitt Gray Committed by Jonathan Cameron
Browse files

counter: Implement events_queue_size sysfs attribute 



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: default avatarWilliam Breathitt Gray <vilhelm.gray@gmail.com>
Link: https://lore.kernel.org/r/c914b2db2ea0a2637633bcc3e86ded3c94783f2e.1632884256.git.vilhelm.gray@gmail.com


Signed-off-by: default avatarJonathan Cameron <Jonathan.Cameron@huawei.com>
parent 4bdec61d

Documentation/ABI/testing/sysfs-bus-counter

+8 −0
Original line number Diff line number Diff line
@@ -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

drivers/counter/counter-sysfs.c

+45 −0
Original line number Diff line number Diff line
@@ -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];