leds: add oneshot blink functions

Add two new functions, led_blink_set_oneshot and
led_trigger_blink_oneshot, to be used by triggers for one-shot blink of
led devices.

This is implemented extending the existing software-blink code, and uses
the same timer and handler function.

The behavior of the code is to do a blink-on, blink-off sequence when
the function is called, ignoring other calls until the sequence is
completed so that the leds keep blinking at constant rate if the
functions are called repeatedly.

This is meant to be used by drivers which needs to trigger on sporadic
event, but doesn't have clear busy/idle trigger points.

After the blink sequence the led remains off. This behavior can be
inverted setting the "invert" argument, which blink the led off, than on
and leave the led on after the sequence.

(bryan.wu@canonical.com: rebase to commit 'leds: don't disable blinking
when writing the same value to delay_on or delay_off')

Signed-off-by: Fabio Baltieri <fabio.baltieri@gmail.com>
Acked-by: Shuah Khan <shuahkhan@gmail.com>
Signed-off-by: Bryan Wu <bryan.wu@canonical.com>

1 files changed, 19 insertions, 0 deletions

diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
index e663e6f413e9..81eb0916b44a 100644
--- a/drivers/leds/led-class.c
+++ b/drivers/leds/led-class.c
@@ -86,6 +86,11 @@ static void led_timer_function(unsigned long data)
 		return;
 	}
 
+	if (led_cdev->flags & LED_BLINK_ONESHOT_STOP) {
+		led_cdev->flags &= ~LED_BLINK_ONESHOT_STOP;
+		return;
+	}
+
 	brightness = led_get_brightness(led_cdev);
 	if (!brightness) {
 		/* Time to switch the LED on. */
@@ -102,6 +107,20 @@ static void led_timer_function(unsigned long data)
 
 	led_set_brightness(led_cdev, brightness);
 
+	/* Return in next iteration if led is in one-shot mode and we are in
+	 * the final blink state so that the led is toggled each delay_on +
+	 * delay_off milliseconds in worst case.
+	 */
+	if (led_cdev->flags & LED_BLINK_ONESHOT) {
+		if (led_cdev->flags & LED_BLINK_INVERT) {
+			if (brightness)
+				led_cdev->flags |= LED_BLINK_ONESHOT_STOP;
+		} else {
+			if (!brightness)
+				led_cdev->flags |= LED_BLINK_ONESHOT_STOP;
+		}
+	}
+
 	mod_timer(&led_cdev->blink_timer, jiffies + msecs_to_jiffies(delay));
 }