From mboxrd@z Thu Jan 1 00:00:00 1970 From: Laurent Pinchart Subject: Re: [PATCHv4] video: backlight: gpio-backlight: Add DT support. Date: Thu, 24 Oct 2013 00:38:59 +0200 Message-ID: <2730370.0UKsY9Ox0H@avalon> References: <20131019104555.GI18477@ns203013.ovh.net> <5267FE81.3070201@wwwdotorg.org> <20131023202011.GD8828@mithrandir> Mime-Version: 1.0 Content-Type: multipart/signed; boundary="nextPart2597348.4gFW9HCYSv"; micalg="pgp-sha1"; protocol="application/pgp-signature" Return-path: In-Reply-To: <20131023202011.GD8828@mithrandir> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Thierry Reding Cc: Stephen Warren , Jean-Christophe PLAGNIOL-VILLARD , Denis Carikli , Mark Rutland , devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Ian Campbell , Eric B??nard , Pawel Moll , Jingoo Han , Rob Herring , Richard Purdie , Sascha Hauer , linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, Lothar Wa??mann List-Id: devicetree@vger.kernel.org --nextPart2597348.4gFW9HCYSv Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" 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 --nextPart2597348.4gFW9HCYSv Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part. Content-Transfer-Encoding: 7Bit -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (GNU/Linux) iQEcBAABAgAGBQJSaFAJAAoJEIkPb2GL7hl1tcAH/jOWVw31RkmsLDJiiTjn4xv6 cOm2Waldra89zG/LNDoAlEPv8af6ngTHkxst2S6Pb3OQjWjV1yYivnsu7rVxOdhu SDr3oJJsB2yu9aUTokP9w70GEzjjpHDlrE1jg9Su0QEyuW4S5mvLORu0JaxpetzC GzlMjTOLrj2lRsyIESGObBoyHBSFihdoIjbnTUM1AWaN7LATImlputRVwKiSrFL1 eKAWC8AGDLtPNkM3svIvM7yCfRo+35xn84hcKvY8MK5+6BXda9GwDMOgxWBJRxuE Fni8hB2GiCmv2GEWE2WNJ72zT/xtqYENJjIVdZ1PbWkYsdVLRLVjCm1LjTLki0E= =xWg5 -----END PGP SIGNATURE----- --nextPart2597348.4gFW9HCYSv-- -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html