Hi Thierry, On Wednesday 23 October 2013 22:20:12 Thierry Reding wrote: > On Wed, Oct 23, 2013 at 05:51:13PM +0100, Stephen Warren wrote: > > On 10/22/2013 09:01 PM, Thierry Reding wrote: > > > On Tue, Oct 22, 2013 at 05:34:45PM +0200, Jean-Christophe > > > > > PLAGNIOL-VILLARD wrote: > > ... > > > > >> I'm sorry but the blacklight descibe in DT have nothing to do > > >> with the common pratice that the current driver have today > > > > > > That's not at all what I said. What I said was that the majority > > > of backlight drivers currently default to turning the backlight on > > > when probed. Therefore I think it would be consistent if this > > > driver did the same. > > > > > > I also said that I don't think it's a very good default, but at the > > > same time we can't just go and change the default behaviour at will > > > because people may rely on it. > > > > It may well be reasonable to change the default behaviour for devices > > instantiated from DT. If it's not possible to instantiate the device > > from DT yet, then it's not possible for anyone to be relying on the > > default behaviour yet, since there is none. So, perhaps the default > > could be: > > > > * If device instantiated from a board file, default to on, for > > backwards-compatibility. > > > > * If device instantiated from DT, there is no backwards compatibility > > to be concerned with, since this is a new feature, hence default to > > off, since we think that's the correct thing to do. > > I actually had a patch to do precisely that. However I then realized > that people have actually been using pwm-backlight in DT for a while > already and therefore may be relying on that behaviour as well. > > It also isn't really an issue of DT vs. non-DT. The simple fact is that > besides the backlight driver there's usually no other code that enables > a backlight on boot. The only way to do so that I know of is using the > DRM panel patches that I've been working on. I would very much welcome a refactoring of the backlight code that would remove the fbdev dependency and hook backlights to panel drivers. That's something I wanted to work on myself, but that I pushed back after CDF :-) > That said, it is true that the number of DT users of the pwm-backlight > driver is smaller than the number of board file users, and it is much > more likely that people are still actively using them, so if we can get > everyone to agree on changing the default behaviour that might still be > possible. -- Regards, Laurent Pinchart
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