Commit b8c5099b authored by Hans de Goede's avatar Hans de Goede Committed by Darren Hart
Browse files

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: default avatarHans de Goede <hdegoede@redhat.com>
Acked-by: default avatarPavel Machek <pavel@ucw.cz>
Signed-off-by: default avatarJacek Anaszewski <jacek.anaszewski@gmail.com>
parent 5ffa572a

Documentation/ABI/testing/sysfs-class-led

+17 −0
Original line number Diff line number Diff line
@@ -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

Documentation/leds/leds-class.txt

+15 −0
Original line number Diff line number Diff line
@@ -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

==================================

drivers/leds/Kconfig

+9 −0
Original line number Diff line number Diff line
@@ -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

drivers/leds/led-class.c

+76 −0
Original line number Diff line number Diff line
@@ -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);

include/linux/leds.h

+15 −0
Original line number Diff line number Diff line
@@ -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>
@@ -46,6 +47,7 @@ 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;
@@ -110,6 +112,11 @@ 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;

};
@@ -422,4 +429,12 @@ 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 */

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