On Sun 2017-02-26 18:10:56, Jacek Anaszewski wrote: > On 02/23/2017 10:23 PM, Heiner Kallweit wrote: > > Am 23.02.2017 um 22:08 schrieb Pavel Machek: > >> On Wed 2017-02-22 21:35:52, Heiner Kallweit wrote: > >>> When registering a LED device we have the option to set a default trigger. > >>> Depending on load order of drivers this trigger may not be available yet. > >>> (affected LED device in my case: a DT-configured GPIO LED) > >>> So far if the default trigger can't be found this error is silently > >>> ignored. > >>> > >>> Let's change this to return EPROBE_DEFER if the default trigger can't be > >>> found. This gives the system the chance to probe the LED device later > >>> once the trigger is available. > >> > >> I see a lot of EPROBE_DEFERs on N900, and it is quite nasty, as it > >> spams a log a lot. > >> > > Usually error messages are printed only if there is an error and it is not > > EPROBE_DEFER. However indeed there still may be several drivers not > > taking into account that a subsystem they depend on may return > > EPROBE_DEFER and this should not be treated as "hard error". > > > >> Rather then re-trying LED registration few times, could we make sure > >> leds are always registered after triggers or something like that? > >> > > I'm afraid if guaranteeing a particular order would be possible w/o > > significant effort then the whole deferred probing concept wouldn't exist. > > > > I could imagine that we can try reordering definitions in the DTS to > > ensure a certain load order. But this might be somewhat fragile. > > So using the existing concept of deferred probing seems to me to be > > the cleaner solution. > > We could go for a solution similar to v4l2-async.c mechanism which > allows for deferring video pipeline linking until all video pipeline > entities are probed, but in the LED subsystem case I think it would be > an overengineering. V4L2 media device has to wait for completion of > probing of several v4l2 drivers, whereas here we've got to wait for > a single driver. EPROBE_DEFER seems to fit for that ideally. I was more thinking of ... just initialize all triggers earlier then all LEDs? Initcalls do have few levels we could use.. 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
