Messages in this thread | | | Date | Mon, 23 Apr 2012 15:45:46 +1000 | From | NeilBrown <> | Subject | Re: [PATCH ] leds: add new transient trigger for one shot timer support |
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On Mon, 23 Apr 2012 07:29:59 +0200 Jonas Bonn <jonas@southpole.se> wrote:
> > On Mon, 2012-04-23 at 11:56 +1000, NeilBrown wrote: > > I wonder if we should allow control of the brightness during the "on" time as > > well. > > You could set the brightness after enabling the timer, but awkward pauses or > > races could then leave the "led" permanently on. > > echo transient > trigger > echo 200 > duration > echo 1 > activate context switch - lots of IO - time passes, 200ms or more, led gets turned of and then back to: > echo 100 > brightness
led gets turned on and there is nothing to turn it off.
Not a likely case I agree, but not impossible.
The problem is that just setting the brightness will turn the led on independent of the start of the trigger (unless you set the brightness to 0 - that disables the trigger).
Thanks, NeilBrown
> > Worst case, the brightness doesn't get set and you get a 'bright' LED > until it expires... but at least it does expire! > > > > > Possibly we could hook into led_set_brightness() and restart the timer > > whenever the brightness was set - and remember the setting. > > An easy way to do this might be to check the brightness setting at the > time the timer expires and save this value. Next time the LED is > activated, we use this brightness setting instead of FULL_ON. It would > be nice to keep this trigger self-contained and not have to hook into > led_set_brightness > > You make interesting point about using the brightness property as the > actual timer trigger, though. That's pretty elegant, but it does > require hooking into led_set_brightness. > > /Jonas
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