Commit 29d76dfa authored by Henrique de Moraes Holschuh's avatar Henrique de Moraes Holschuh Committed by Richard Purdie
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leds: Add support to leds with readable status 



Some led hardware allows drivers to query the led state, and this patch
adds a hook to let the led class take advantage of that information when
available.

Without this functionality, when access to the led hardware is not
exclusive (i.e. firmware or hardware might change its state behind the
kernel's back), reality goes out of sync with the led class' idea of what
the led is doing, which is annoying at best.

Behaviour for drivers that do not or cannot read the led status is
unchanged.

Signed-off-by: default avatarHenrique de Moraes Holschuh <hmh@hmh.eng.br>
Signed-off-by: default avatarRichard Purdie <rpurdie@rpsys.net>
parent ca3259b3

drivers/leds/led-class.c

+9 −0
Original line number Diff line number Diff line
@@ -24,6 +24,12 @@ 


static struct class *leds_class;



static void led_update_brightness(struct led_classdev *led_cdev)

{

	if (led_cdev->brightness_get)

		led_cdev->brightness = led_cdev->brightness_get(led_cdev);

}



static ssize_t led_brightness_show(struct device *dev, 

		struct device_attribute *attr, char *buf)

{
@@ -31,6 +37,7 @@ static ssize_t led_brightness_show(struct device *dev, 
	ssize_t ret = 0;



	/* no lock needed for this */

	led_update_brightness(led_cdev);

	sprintf(buf, "%u\n", led_cdev->brightness);

	ret = strlen(buf) + 1;
@@ -113,6 +120,8 @@ int led_classdev_register(struct device *parent, struct led_classdev *led_cdev) 
	list_add_tail(&led_cdev->node, &leds_list);

	up_write(&leds_list_lock);



	led_update_brightness(led_cdev);



#ifdef CONFIG_LEDS_TRIGGERS

	init_rwsem(&led_cdev->trigger_lock);

include/linux/leds.h

+2 −0
Original line number Diff line number Diff line
@@ -37,6 +37,8 @@ struct led_classdev { 
	/* Set LED brightness level */

	void		(*brightness_set)(struct led_classdev *led_cdev,

					  enum led_brightness brightness);

	/* Get LED brightness level */

	enum led_brightness (*brightness_get)(struct led_classdev *led_cdev);



	/* Activate hardware accelerated blink */

	int		(*blink_set)(struct led_classdev *led_cdev,

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