Commit 11f70002 authored by Akinobu Mita's avatar Akinobu Mita Committed by Pavel
Browse files

leds: remove PAGE_SIZE limit of /sys/class/leds/<led>/trigger 



Reading /sys/class/leds/<led>/trigger returns all available LED triggers.
However, the size of this file is limited to PAGE_SIZE because of the
limitation for sysfs attribute.

Enabling LED CPU trigger on systems with thousands of CPUs easily hits
PAGE_SIZE limit, and makes it impossible to see all available LED triggers
and which trigger is currently activated.

We work around it here by converting /sys/class/leds/<led>/trigger to
binary attribute, which is not limited by length. This is _not_ good
design, do not copy it.

Signed-off-by: default avatarAkinobu Mita <akinobu.mita@gmail.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Dan Murphy <dmurphy@ti.com>A
Reviewed-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarPavel Machek <pavel@ucw.cz>
parent a2cafdfd

drivers/leds/led-class.c

+4 −4
Original line number Diff line number Diff line
@@ -74,13 +74,13 @@ static ssize_t max_brightness_show(struct device *dev, 
static DEVICE_ATTR_RO(max_brightness);



#ifdef CONFIG_LEDS_TRIGGERS

static DEVICE_ATTR(trigger, 0644, led_trigger_show, led_trigger_store);

static struct attribute *led_trigger_attrs[] = {

	&dev_attr_trigger.attr,

static BIN_ATTR(trigger, 0644, led_trigger_read, led_trigger_write, 0);

static struct bin_attribute *led_trigger_bin_attrs[] = {

	&bin_attr_trigger,

	NULL,

};

static const struct attribute_group led_trigger_group = {

	.attrs = led_trigger_attrs,

	.bin_attrs = led_trigger_bin_attrs,

};

#endif

drivers/leds/led-triggers.c

+68 −22
Original line number Diff line number Diff line
@@ -16,6 +16,7 @@ 
#include <linux/rwsem.h>

#include <linux/leds.h>

#include <linux/slab.h>

#include <linux/mm.h>

#include "leds.h"



/*
@@ -26,9 +27,11 @@ LIST_HEAD(trigger_list); 


 /* Used by LED Class */



ssize_t led_trigger_store(struct device *dev, struct device_attribute *attr,

		const char *buf, size_t count)

ssize_t led_trigger_write(struct file *filp, struct kobject *kobj,

			  struct bin_attribute *bin_attr, char *buf,

			  loff_t pos, size_t count)

{

	struct device *dev = kobj_to_dev(kobj);

	struct led_classdev *led_cdev = dev_get_drvdata(dev);

	struct led_trigger *trig;

	int ret = count;
@@ -64,39 +67,82 @@ unlock: 
	mutex_unlock(&led_cdev->led_access);

	return ret;

}

EXPORT_SYMBOL_GPL(led_trigger_store);

EXPORT_SYMBOL_GPL(led_trigger_write);



ssize_t led_trigger_show(struct device *dev, struct device_attribute *attr,

		char *buf)

__printf(3, 4)

static int led_trigger_snprintf(char *buf, ssize_t size, const char *fmt, ...)

{

	va_list args;

	int i;



	va_start(args, fmt);

	if (size <= 0)

		i = vsnprintf(NULL, 0, fmt, args);

	else

		i = vscnprintf(buf, size, fmt, args);

	va_end(args);



	return i;

}



static int led_trigger_format(char *buf, size_t size,

			      struct led_classdev *led_cdev)

{

	struct led_classdev *led_cdev = dev_get_drvdata(dev);

	struct led_trigger *trig;

	int len = 0;

	int len = led_trigger_snprintf(buf, size, "%s",

				       led_cdev->trigger ? "none" : "[none]");



	list_for_each_entry(trig, &trigger_list, next_trig) {

		bool hit = led_cdev->trigger &&

			!strcmp(led_cdev->trigger->name, trig->name);



		len += led_trigger_snprintf(buf + len, size - len,

					    " %s%s%s", hit ? "[" : "",

					    trig->name, hit ? "]" : "");

	}



	len += led_trigger_snprintf(buf + len, size - len, "\n");



	return len;

}



/*

 * It was stupid to create 10000 cpu triggers, but we are stuck with it now.

 * Don't make that mistake again. We work around it here by creating binary

 * attribute, which is not limited by length. This is _not_ good design, do not

 * copy it.

 */

ssize_t led_trigger_read(struct file *filp, struct kobject *kobj,

			struct bin_attribute *attr, char *buf,

			loff_t pos, size_t count)

{

	struct device *dev = kobj_to_dev(kobj);

	struct led_classdev *led_cdev = dev_get_drvdata(dev);

	void *data;

	int len;



	down_read(&triggers_list_lock);

	down_read(&led_cdev->trigger_lock);



	if (!led_cdev->trigger)

		len += scnprintf(buf+len, PAGE_SIZE - len, "[none] ");

	else

		len += scnprintf(buf+len, PAGE_SIZE - len, "none ");



	list_for_each_entry(trig, &trigger_list, next_trig) {

		if (led_cdev->trigger && !strcmp(led_cdev->trigger->name,

							trig->name))

			len += scnprintf(buf+len, PAGE_SIZE - len, "[%s] ",

					 trig->name);

		else

			len += scnprintf(buf+len, PAGE_SIZE - len, "%s ",

					 trig->name);

	len = led_trigger_format(NULL, 0, led_cdev);

	data = kvmalloc(len + 1, GFP_KERNEL);

	if (!data) {

		up_read(&led_cdev->trigger_lock);

		up_read(&triggers_list_lock);

		return -ENOMEM;

	}

	len = led_trigger_format(data, len + 1, led_cdev);



	up_read(&led_cdev->trigger_lock);

	up_read(&triggers_list_lock);



	len += scnprintf(len+buf, PAGE_SIZE - len, "\n");

	len = memory_read_from_buffer(buf, count, &pos, data, len);



	kvfree(data);



	return len;

}

EXPORT_SYMBOL_GPL(led_trigger_show);

EXPORT_SYMBOL_GPL(led_trigger_read);



/* Caller must ensure led_cdev->trigger_lock held */

int led_trigger_set(struct led_classdev *led_cdev, struct led_trigger *trig)

drivers/leds/leds.h

+6 −0
Original line number Diff line number Diff line
@@ -23,6 +23,12 @@ void led_set_brightness_nopm(struct led_classdev *led_cdev, 
				enum led_brightness value);

void led_set_brightness_nosleep(struct led_classdev *led_cdev,

				enum led_brightness value);

ssize_t led_trigger_read(struct file *filp, struct kobject *kobj,

			struct bin_attribute *attr, char *buf,

			loff_t pos, size_t count);

ssize_t led_trigger_write(struct file *filp, struct kobject *kobj,

			struct bin_attribute *bin_attr, char *buf,

			loff_t pos, size_t count);



extern struct rw_semaphore leds_list_lock;

extern struct list_head leds_list;

include/linux/leds.h

+0 −5
Original line number Diff line number Diff line
@@ -361,11 +361,6 @@ struct led_trigger { 
#define led_trigger_get_led(dev)	((struct led_classdev *)dev_get_drvdata((dev)))

#define led_trigger_get_drvdata(dev)	(led_get_trigger_data(led_trigger_get_led(dev)))



ssize_t led_trigger_store(struct device *dev, struct device_attribute *attr,

			const char *buf, size_t count);

ssize_t led_trigger_show(struct device *dev, struct device_attribute *attr,

			char *buf);



/* Registration functions for complex triggers */

extern int led_trigger_register(struct led_trigger *trigger);

extern void led_trigger_unregister(struct led_trigger *trigger);

CRA Git | Maintained and supported by SUSTech CRA and CCSE