leds: Add support for hardware accelerated LED flashing

Extends the leds subsystem with a blink_set() callback function which can
be optionally implemented by a LED driver. If implemented, the driver can use
the hardware acceleration for blinking a LED.

Signed-off-by: Márton Németh <nm127@freemail.hu>
Signed-off-by: Richard Purdie <rpurdie@rpsys.net>

include/linux/leds.h

@@ -38,6 +38,11 @@ struct led_classdev {
 	void		(*brightness_set)(struct led_classdev *led_cdev,
 					  enum led_brightness brightness);
 
+	/* Activate hardware accelerated blink */
+	int		(*blink_set)(struct led_classdev *led_cdev,
+				     unsigned long *delay_on,
+				     unsigned long *delay_off);
+
 	struct device		*dev;
 	struct list_head	 node;			/* LED Device list */
 	char			*default_trigger;	/* Trigger to use */