On Wednesday, October 23, 2013 5:02 AM, Thierry Reding wrote: > On Tue, Oct 22, 2013 at 05:34:45PM +0200, Jean-Christophe PLAGNIOL-VILLARD wrote: > > On 09:23 Tue 22 Oct , Thierry Reding wrote: > > > On Tue, Oct 22, 2013 at 06:58:33AM +0200, Jean-Christophe PLAGNIOL-VILLARD wrote: > > > > On 11:13 Mon 21 Oct , Denis Carikli wrote: > > > > > Cc: Richard Purdie <rpurdie@xxxxxxxxx> > > > > > Cc: Jingoo Han <jg1.han@xxxxxxxxxxx> > > > > > Cc: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> > > > > > Cc: Rob Herring <rob.herring@xxxxxxxxxxx> > > > > > Cc: Pawel Moll <pawel.moll@xxxxxxx> > > > > > Cc: Mark Rutland <mark.rutland@xxxxxxx> > > > > > Cc: Stephen Warren <swarren@xxxxxxxxxxxxx> > > > > > Cc: Ian Campbell <ijc+devicetree@xxxxxxxxxxxxxx> > > > > > Cc: devicetree@xxxxxxxxxxxxxxx > > > > > Cc: Sascha Hauer <kernel@xxxxxxxxxxxxxx> > > > > > Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > > > > > Cc: Lothar Waßmann <LW@xxxxxxxxxxxxxxxxxxx> > > > > > Cc: Jean-Christophe Plagniol-Villard <plagnioj@xxxxxxxxxxxx> > > > > > Cc: Eric Bénard <eric@xxxxxxxxxx> > > > > > Signed-off-by: Denis Carikli <denis@xxxxxxxxxx> > > > > > --- > > > > > ChangeLog v3->v4: > > > > > - The default-brightness property is now optional, it defaults to 1 if not set. > > > > by default we set OFF not ON > > > > > > > > do not actiate driver or properti by default you can not known to consequence > > > > on the hw > > > > > > Turning on a backlight by default is what pretty much every backlight > > > driver does. I personally think that's the wrong default, I even tried > > > to get some discussion started recently about how we could change this. > > > However, given that this has been the case for possibly as long as the > > > subsystem has existed, suddenly changing it might cause quite a few of > > > our users to boot the new kernel and not see their display come up. As > > > with any other ABI, this isn't something we can just change without a > > > very good migration path. > > > > 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. I agree with your opinion. But, I can't decide how to change it. > > > put on by default if wrong specially without the property define. Even put it > > on by default it wrong as the bootloader may have set it already for splash > > screen and to avoid glitch the drivers need to detect this. > > I agree that would be preferable, but I don't know of any way to detect > what value the bootloader set a GPIO to. The GPIO API requires that you > call gpio_direction_output(), and that requires a value parameter which > will be used as the output level of the GPIO. Jean-Christophe's point is right. We may need to discuss 'the way to detect what value the bootloader set a GPIO to'. > > For me this should not even be a property but handled by the driver them > > selves in C. > > Agreed. There has been some discussion recently about whether devicetree > should be extended (or supplemented) to allow defining behaviour as well > (in addition to just hardware). But that's not immediately relevant here > at this time. Agreed. Best regards, Jingoo Han -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
