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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: Akinobu 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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Pavel Machek <pavel@ucw.cz>
This commit is contained in:
Akinobu Mita 2019-09-29 23:18:49 +09:00 committed by Pavel
parent a2cafdfd8c
commit 11f7000221
4 changed files with 78 additions and 31 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
drivers/leds/led-class.c
View File

@ -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

90
drivers/leds/led-triggers.c
View File

@ -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 @@ ssize_t led_trigger_store(struct device *dev, struct device_attribute *attr,
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)

6
drivers/leds/leds.h
View File

@ -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;

5
include/linux/leds.h
View File

@ -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);