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leds: class: Add new optional brightness_hw_changed attribute 

Some LEDs may have their brightness level changed autonomously
(outside of kernel control) by hardware / firmware. This commit
adds support for an optional brightness_hw_changed attribute to
signal such changes to userspace (if a driver can detect them):

What:		/sys/class/leds/<led>/brightness_hw_changed
Date:		January 2017
KernelVersion:	4.11
Description:
		Last hardware set brightness level for this LED. Some LEDs
		may be changed autonomously by hardware/firmware. Only LEDs
		where this happens and the driver can detect this, will
		have this file.

		This file supports poll() to detect when the hardware
		changes the brightness.

		Reading this file will return the last brightness level set
		by the hardware, this may be different from the current
		brightness.

Drivers which want to support this, simply add LED_BRIGHT_HW_CHANGED to
their flags field and call led_classdev_notify_brightness_hw_changed()
with the hardware set brightness when they detect a hardware / firmware
triggered brightness change.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>
zero-colors
Hans de Goede 2017-01-29 14:42:52 +01:00 committed by Jacek Anaszewski
parent cbe99c538d
commit 0cb8eb30d4
5 changed files with 132 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
Documentation/ABI/testing/sysfs-class-led
View File

@ -23,6 +23,23 @@ Description:
If the LED does not support different brightness levels, this
should be 1.
What: /sys/class/leds/<led>/brightness_hw_changed
Date: January 2017
KernelVersion: 4.11
Description:
Last hardware set brightness level for this LED. Some LEDs
may be changed autonomously by hardware/firmware. Only LEDs
where this happens and the driver can detect this, will have
this file.
This file supports poll() to detect when the hardware changes
the brightness.
Reading this file will return the last brightness level set
by the hardware, this may be different from the current
brightness. Reading this file when no hw brightness change
event has happened will return an ENODATA error.
What: /sys/class/leds/<led>/trigger
Date: March 2006
KernelVersion: 2.6.17

15
Documentation/leds/leds-class.txt
View File

@ -65,6 +65,21 @@ LED subsystem core exposes following API for setting brightness:
blinking, returns -EBUSY if software blink fallback is enabled.
LED registration API
====================
A driver wanting to register a LED classdev for use by other drivers /
userspace needs to allocate and fill a led_classdev struct and then call
[devm_]led_classdev_register. If the non devm version is used the driver
must call led_classdev_unregister from its remove function before
free-ing the led_classdev struct.
If the driver can detect hardware initiated brightness changes and thus
wants to have a brightness_hw_changed attribute then the LED_BRIGHT_HW_CHANGED
flag must be set in flags before registering. Calling
led_classdev_notify_brightness_hw_changed on a classdev not registered with
the LED_BRIGHT_HW_CHANGED flag is a bug and will trigger a WARN_ON.
Hardware accelerated blink of LEDs
==================================

9
drivers/leds/Kconfig
View File

@ -29,6 +29,15 @@ config LEDS_CLASS_FLASH
for the flash related features of a LED device. It can be built
as a module.
config LEDS_BRIGHTNESS_HW_CHANGED
bool "LED Class brightness_hw_changed attribute support"
depends on LEDS_CLASS
help
This option enables support for the brightness_hw_changed attribute
for led sysfs class devices under /sys/class/leds.
See Documentation/ABI/testing/sysfs-class-led for details.
comment "LED drivers"
config LEDS_88PM860X

76
drivers/leds/led-class.c
View File

@ -103,6 +103,68 @@ static const struct attribute_group *led_groups[] = {
NULL,
};
#ifdef CONFIG_LEDS_BRIGHTNESS_HW_CHANGED
static ssize_t brightness_hw_changed_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct led_classdev *led_cdev = dev_get_drvdata(dev);
if (led_cdev->brightness_hw_changed == -1)
return -ENODATA;
return sprintf(buf, "%u\n", led_cdev->brightness_hw_changed);
}
static DEVICE_ATTR_RO(brightness_hw_changed);
static int led_add_brightness_hw_changed(struct led_classdev *led_cdev)
{
struct device *dev = led_cdev->dev;
int ret;
ret = device_create_file(dev, &dev_attr_brightness_hw_changed);
if (ret) {
dev_err(dev, "Error creating brightness_hw_changed\n");
return ret;
}
led_cdev->brightness_hw_changed_kn =
sysfs_get_dirent(dev->kobj.sd, "brightness_hw_changed");
if (!led_cdev->brightness_hw_changed_kn) {
dev_err(dev, "Error getting brightness_hw_changed kn\n");
device_remove_file(dev, &dev_attr_brightness_hw_changed);
return -ENXIO;
}
return 0;
}
static void led_remove_brightness_hw_changed(struct led_classdev *led_cdev)
{
sysfs_put(led_cdev->brightness_hw_changed_kn);
device_remove_file(led_cdev->dev, &dev_attr_brightness_hw_changed);
}
void led_classdev_notify_brightness_hw_changed(struct led_classdev *led_cdev,
enum led_brightness brightness)
{
if (WARN_ON(!led_cdev->brightness_hw_changed_kn))
return;
led_cdev->brightness_hw_changed = brightness;
sysfs_notify_dirent(led_cdev->brightness_hw_changed_kn);
}
EXPORT_SYMBOL_GPL(led_classdev_notify_brightness_hw_changed);
#else
static int led_add_brightness_hw_changed(struct led_classdev *led_cdev)
{
return 0;
}
static void led_remove_brightness_hw_changed(struct led_classdev *led_cdev)
{
}
#endif
/**
* led_classdev_suspend - suspend an led_classdev.
* @led_cdev: the led_classdev to suspend.
@ -204,9 +266,20 @@ int led_classdev_register(struct device *parent, struct led_classdev *led_cdev)
dev_warn(parent, "Led %s renamed to %s due to name collision",
led_cdev->name, dev_name(led_cdev->dev));
if (led_cdev->flags & LED_BRIGHT_HW_CHANGED) {
ret = led_add_brightness_hw_changed(led_cdev);
if (ret) {
device_unregister(led_cdev->dev);
return ret;
}
}
led_cdev->work_flags = 0;
#ifdef CONFIG_LEDS_TRIGGERS
init_rwsem(&led_cdev->trigger_lock);
#endif
#ifdef CONFIG_LEDS_BRIGHTNESS_HW_CHANGED
led_cdev->brightness_hw_changed = -1;
#endif
mutex_init(&led_cdev->led_access);
/* add to the list of leds */
@ -256,6 +329,9 @@ void led_classdev_unregister(struct led_classdev *led_cdev)
flush_work(&led_cdev->set_brightness_work);
if (led_cdev->flags & LED_BRIGHT_HW_CHANGED)
led_remove_brightness_hw_changed(led_cdev);
device_unregister(led_cdev->dev);
down_write(&leds_list_lock);

15
include/linux/leds.h
View File

@ -13,6 +13,7 @@
#define __LINUX_LEDS_H_INCLUDED
#include <linux/device.h>
#include <linux/kernfs.h>
#include <linux/list.h>
#include <linux/mutex.h>
#include <linux/rwsem.h>
@ -47,6 +48,7 @@ struct led_classdev {
#define LED_DEV_CAP_FLASH (1 << 18)
#define LED_HW_PLUGGABLE (1 << 19)
#define LED_PANIC_INDICATOR (1 << 20)
#define LED_BRIGHT_HW_CHANGED (1 << 21)
/* set_brightness_work / blink_timer flags, atomic, private. */
unsigned long work_flags;
@ -111,6 +113,11 @@ struct led_classdev {
bool activated;
#endif
#ifdef CONFIG_LEDS_BRIGHTNESS_HW_CHANGED
int brightness_hw_changed;
struct kernfs_node *brightness_hw_changed_kn;
#endif
/* Ensures consistent access to the LED Flash Class device */
struct mutex led_access;
};
@ -423,4 +430,12 @@ static inline void ledtrig_cpu(enum cpu_led_event evt)
}
#endif
#ifdef CONFIG_LEDS_BRIGHTNESS_HW_CHANGED
extern void led_classdev_notify_brightness_hw_changed(
struct led_classdev *led_cdev, enum led_brightness brightness);
#else
static inline void led_classdev_notify_brightness_hw_changed(
struct led_classdev *led_cdev, enum led_brightness brightness) { }
#endif
#endif /* __LINUX_LEDS_H_INCLUDED */