On Wed 2015-07-01 12:47:02, Jacek Anaszewski wrote: > On 07/01/2015 09:43 AM, Pavel Machek wrote: > >On Wed 2015-07-01 09:28:52, Jacek Anaszewski wrote: > >>On 06/30/2015 07:46 PM, Pavel Machek wrote: > >>>On Tue 2015-06-30 15:06:19, Jacek Anaszewski wrote: > >>>>On 06/30/2015 01:58 PM, Pavel Machek wrote: > >>>>>On Tue 2015-06-30 10:01:08, Jacek Anaszewski wrote: > >>>>>>This patch rearranges the core LED subsystem code, so that it > >>>>>>now removes from drivers the responsibility of using work queues > >>>>>>internally in case their brightness_set ops can sleep. > >>>>>>Addition of two flags: LED_BRIGHTNESS_FAST and LED_BLINK_DISABLE > >>>>>>as well as new_brightness_value property to the struct led_classdev > >>>>>>allows for employing existing set_brightness_work to do the job. > >>>>>>The modifications allow also to get rid of brightness_set_sync op, > >>>>>>as flash LED devices can now be handled properly only basing on the > >>>>>>SET_BRIGHTNESS_SYNC flag. > >>>>> > >>>>>Are you sure this is good idea? > >>>>> > >>>>>You'll now use single callback for blocking and non-blocking > >>>>>behaviour. I'm pretty sure stuff like lockdep will have some fun with > >>>>>that. > >>>> > >>>>I enabled "Lock Debugging" options and didn't get any warning. > >>>>Could you describe the use case you are thinking of? > >>> > >>>You may get one when one of the sleeping functions uses some lock... > >> > >>Drivers which use spin_lock in their brightness_set op will have to > >>set LED_BRIGHTNESS_FAST flag, which will instruct the LED core to > >>call the op synchronously. On the other hand drivers which can sleep > >>in their brightness_set op won't set the flag, which will make LED core > >>delegating the op to the work queue task. It is also possible that > >>driver with brightness_set op that can sleep set SET_BRIGHTNESS_SYNC > >>flag - then LED core will call it in a synchronous way from > >>led_brightness_set and it will schedule work queue task in case > >>the op is called from triggers. > > > >I understand this "works". > > > >>If you want to NAK the patch, please come up with detailed analysis > >>on how it can cause problems. Without this I infer that you didn't > >>spend a second on analyzing the code. This is counterproductive. > > > >NAK. > > > >Because calling two functions with different semantics through same > >function pointer is extremely ugly, and _will_ cause lockdep > >problems. Talk to the lockdep people for details. > > Which two functions are you thinking of? There is a single > brightness_set op to call. Yes, and brightness_set may or may not sleep according to a flag somewhere. Just use two function pointers, one of them will be always NULL. You can keep the flag if you want to. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- To unsubscribe from this list: send the line "unsubscribe linux-leds" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
