Re: [PATCH v2] leds: fix brightness changing when software blinking is active

[Pavel Machek <pavel@ucw.cz>]

On Tue 2015-06-23 19:59:27, Stas Sergeev wrote:
> 02.05.2015 17:59, Pavel Machek пишет:
> > On Thu 2015-05-14 18:24:02, Stas Sergeev wrote:
> >>
> >> The following sequence:
> >> echo timer >/sys/class/leds/<name>/trigger
> >> echo 1 >/sys/class/leds/<name>/brightness
> >> should change the ON brightness for blinking.
> >> The function led_set_brightness() was mistakenly initiating the
> >> delayed blink stop procedure, which resulted in no blinking with
> >> the timer trigger still active.
> >>
> >> This patch fixes the problem by changing led_set_brightness()
> >> to not initiate the delayed blink stop when brightness is not 0.
> > 
> > Could we get this part of API documented? It is quite non-obvious... 0 clears the trigger,
> > other values do not, I thought it is a bug when I saw it...
> I guess the thinking was that if ON brightness differs
> from OFF brightness, you should not clear the trigger.
> But if you put ON brightness similar to OFF brightness,
> then you can as well stop blinking at all.

And none of this is documented. So what about this?

diff --git a/Documentation/ABI/testing/sysfs-class-led b/Documentation/ABI/testing/sysfs-class-led
index 3646ec8..b734d7f 100644
--- a/Documentation/ABI/testing/sysfs-class-led
+++ b/Documentation/ABI/testing/sysfs-class-led
@@ -4,16 +4,25 @@ KernelVersion:	2.6.17
 Contact:	Richard Purdie <rpurdie@rpsys.net>
 Description:
 		Set the brightness of the LED. Most LEDs don't
-		have hardware brightness support so will just be turned on for
+		have hardware brightness support, so will just be turned on for
 		non-zero brightness settings. The value is between 0 and
 		/sys/class/leds/<led>/max_brightness.
 
+		Writing 0 to this file clears active trigger.
+
+		Writing non-zero to this file while trigger is active changes the
+		top brightness trigger is going to use.
+		
+
 What:		/sys/class/leds/<led>/max_brightness
 Date:		March 2006
 KernelVersion:	2.6.17
 Contact:	Richard Purdie <rpurdie@rpsys.net>
 Description:
-		Maximum brightness level for this led, default is 255 (LED_FULL).
+		Maximum brightness level for this LED, default is 255 (LED_FULL).
+
+		If the LED does not support different brightness levels, this
+		should be 1.
 
 What:		/sys/class/leds/<led>/trigger
 Date:		March 2006
@@ -21,7 +30,7 @@ KernelVersion:	2.6.17
 Contact:	Richard Purdie <rpurdie@rpsys.net>
 Description:
 		Set the trigger for this LED. A trigger is a kernel based source
-		of led events.
+		of LED events.
 		You can change triggers in a similar manner to the way an IO
 		scheduler is chosen. Trigger specific parameters can appear in
 		/sys/class/leds/<led> once a given trigger is selected.

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