led-class: always implement blinking

Currently, blinking LEDs can be awkward because it is not guaranteed that
all LEDs implement blinking.  The trigger that wants it to blink then
needs to implement its own timer solution.

Rather than require that, add led_blink_set() API that triggers can use.
This function will attempt to use hw blinking, but if that fails
implements a timer for it.  To stop blinking again, brightness_set() also
needs to be wrapped into API that will stop the software blink.

As a result of this, the timer trigger becomes a very trivial one, and
hopefully we can finally see triggers using blinking as well because it's
always easy to use.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Acked-by: Richard Purdie <rpurdie@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 43 insertions, 4 deletions

diff --git a/include/linux/leds.h b/include/linux/leds.h
index ba6986a..0f19df9 100644
--- a/include/linux/leds.h
+++ b/include/linux/leds.h
@@ -15,6 +15,7 @@
 #include <linux/list.h>
 #include <linux/spinlock.h>
 #include <linux/rwsem.h>
+#include <linux/timer.h>
 
 struct device;
 /*
@@ -45,10 +46,14 @@ struct led_classdev {
 	/* Get LED brightness level */
 	enum led_brightness (*brightness_get)(struct led_classdev *led_cdev);
 
-	/* Activate hardware accelerated blink, delays are in
-	 * miliseconds and if none is provided then a sensible default
-	 * should be chosen. The call can adjust the timings if it can't
-	 * match the values specified exactly. */
+	/*
+	 * Activate hardware accelerated blink, delays are in milliseconds
+	 * and if both are zero then a sensible default should be chosen.
+	 * The call should adjust the timings in that case and if it can't
+	 * match the values specified exactly.
+	 * Deactivate blinking again when the brightness is set to a fixed
+	 * value via the brightness_set() callback.
+	 */
 	int		(*blink_set)(struct led_classdev *led_cdev,
 				     unsigned long *delay_on,
 				     unsigned long *delay_off);
@@ -57,6 +62,10 @@ struct led_classdev {
 	struct list_head	 node;			/* LED Device list */
 	const char		*default_trigger;	/* Trigger to use */
 
+	unsigned long		 blink_delay_on, blink_delay_off;
+	struct timer_list	 blink_timer;
+	int			 blink_brightness;
+
 #ifdef CONFIG_LEDS_TRIGGERS
 	/* Protects the trigger data below */
 	struct rw_semaphore	 trigger_lock;
@@ -73,6 +82,36 @@ extern void led_classdev_unregister(struct led_classdev *led_cdev);
 extern void led_classdev_suspend(struct led_classdev *led_cdev);
 extern void led_classdev_resume(struct led_classdev *led_cdev);
 
+/**
+ * led_blink_set - set blinking with software fallback
+ * @led_cdev: the LED to start blinking
+ * @delay_on: the time it should be on (in ms)
+ * @delay_off: the time it should ble off (in ms)
+ *
+ * This function makes the LED blink, attempting to use the
+ * hardware acceleration if possible, but falling back to
+ * software blinking if there is no hardware blinking or if
+ * the LED refuses the passed values.
+ *
+ * Note that if software blinking is active, simply calling
+ * led_cdev->brightness_set() will not stop the blinking,
+ * use led_classdev_brightness_set() instead.
+ */
+extern void led_blink_set(struct led_classdev *led_cdev,
+			  unsigned long *delay_on,
+			  unsigned long *delay_off);
+/**
+ * led_brightness_set - set LED brightness
+ * @led_cdev: the LED to set
+ * @brightness: the brightness to set it to
+ *
+ * Set an LED's brightness, and, if necessary, cancel the
+ * software blink timer that implements blinking when the
+ * hardware doesn't.
+ */
+extern void led_brightness_set(struct led_classdev *led_cdev,
+			       enum led_brightness brightness);
+
 /*
  * LED Triggers
  */