On Tue 2016-11-15 13:06:14, Hans de Goede wrote: > Hi, > > On 15-11-16 12:48, Pavel Machek wrote: > >Hi! > > > >>>>>The LED you are talking about _has_ a trigger, implemented in > >>>>>hardware. That trigger can change LED brightness behind kernel's (and > >>>>>userspace's) back. Don't pretend the trigger does not exist, it does. > >>>>> > >>>>>And when you do that, you'll have nice place to report changes to > >>>>>userspace -- trigger can now export that information, and offer poll() > >>>>>interface. > >>>> > >>>>Well, that sounds interesting. It is logically justifiable. > >>> > >>>Thanks. > >>> > >>>>I initially proposed exactly this solution, with recently > >>>>added userspace LED being a trigger listener. It seems a bit > >>>>awkward though. How would you listen to the trigger events? > >>> > >>>Trigger exposes a file in sysfs, with poll() working on that file > >> > >>Hmm, a new file would give the advantage of making it easy for > >>userspace to see if the trigger is poll-able, this is likely > >>better then my own proposal I just send. > > > >Good. > > > >>>(and > >>>probably read exposing the current brightness). > >> > >>If we do this, can we please make it mirror brightness, iow > >>also make it writable, that will make it easier for userspace > >>to deal with it. We can simply re-use the existing show / store > >>methods for brightness for this. > > > >Actually, echo 0 > brightness disables the trigger, IIRC. I'd avoid > >that here, you want to be able to turn off the backlight but still > >keep the trigger (and be notified of future changes). > > True, that is easy to do the store method will just need to call > led_set_brightness_nosleep instead of led_set_brightness, this > will skip the checks to stop blinking in led_set_brightness and > otherwise is equivalent. > > >>I suggest we call it: > >> > >>trigger_brightness > >> > >>And only register it when a poll-able trigger is present. > > > >I'd call it 'current_brightness', but that's no big deal. Yes, only > >registering it for poll-able triggers makes sense. > > current_brightness works for me. I will take a shot a patch-set > implementing this. Thanks! Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
Attachment:
signature.asc
Description: Digital signature
