Messages in this thread | | | Date | Tue, 12 Jun 2012 09:16:49 +0200 | From | Fabio Baltieri <> | Subject | Re: [PATCH] leds: use led_brightness_set in led_trigger_event |
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On Mon, Jun 11, 2012 at 03:38:25PM -0600, Shuah Khan wrote: > On Mon, 2012-06-11 at 22:57 +0200, Fabio Baltieri wrote: > > Fix led_trigger_event() to use led_brightness_set() instead of > > led_set_brightness(), so that any pending blink timer is stopped before > > setting the new brightness value. Without this fix LED status may be > > overridden by a pending timer. > > > > This allows a trigger to use a mix of led_trigger_event(), > > led_trigger_blink() and led_trigger_blink_oneshot() without races. > > > > Signed-off-by: Fabio Baltieri <fabio.baltieri@gmail.com> > > Cc: Bryan Wu <bryan.wu@canonical.com> > > --- > > Hi Bryan, > > > > I found this one while working on another patch but I think it's also needed by > > other drivers which mixes led_trigger_blink() and led_trigger_event(), such as > > power_supply_leds. > > > > Without this a led don't stop blinking as it should when calling > > led_trigger_event(). > > Good find. This is very subtle race though because both timer and > oneshot triggers call led_brightness_set() from their deactivate > routines. Is this when these events triggered using oneshot trigger?
Actually that was when mixing blink (both timer and oneshot, they use the same timer) and standard trigger-event-set. It should be safe if only internal (core) functions call set_brightness.
> > > > Should not cause any harm on other drivers. > > > > (I'm starting to find the whole led_set_brightness/led_brightness_set thing a > > bit confusing BTW...) > > I agree with the names are confusing. :) It found it confusing as well. > Probably why we have this bug hiding until led_trigger_blink() came > along. > > led_brightness_set() calls led_set_brightness(). led_set_brightness() > takes cares about whether the driver is in suspend state and invokes > driver's brightness_set interface. Maybe led_clear_blink_timer() would > be a better name for this led_brightness_set() routine.
I think maybe we should just rename the function to led_set_brightness() for the safe one (the one whichh also deactivate the time) and _led_set_brightness() for the internal one, to put some emphasis to the "internal" nature of the second.
> I can volunteer to make this change if we agree that this will be a good > one to clear this naming confusion.
That would save some headache in the future! :-)
Fabio
> > -- Shuah > > > > > Fabio > > > > drivers/leds/led-triggers.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/leds/led-triggers.c b/drivers/leds/led-triggers.c > > index fa0b9be..b88d3b9 100644 > > --- a/drivers/leds/led-triggers.c > > +++ b/drivers/leds/led-triggers.c > > @@ -224,7 +224,7 @@ void led_trigger_event(struct led_trigger *trig, > > struct led_classdev *led_cdev; > > > > led_cdev = list_entry(entry, struct led_classdev, trig_list); > > - led_set_brightness(led_cdev, brightness); > > + led_brightness_set(led_cdev, brightness); > > This is in-line with led_trigger_set() which is calling > led_bightness_set() correctly. Also led_classdev_unregister() calls it I > think for the same reason so the blink timer can be stopped. > > > } > > read_unlock(&trig->leddev_list_lock); > > } > >
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