From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thierry Reding Subject: Re: [PATCHv4] video: backlight: gpio-backlight: Add DT support. Date: Tue, 22 Oct 2013 22:01:42 +0200 Message-ID: <20131022200141.GA8037@mithrandir> References: <20131019104555.GI18477@ns203013.ovh.net> <1382346813-8449-1-git-send-email-denis@eukrea.com> <20131022045833.GB17512@ns203013.ovh.net> <20131022072307.GA8681@ulmo.nvidia.com> <20131022153445.GD17512@ns203013.ovh.net> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="1yeeQ81UyVL57Vl7" Return-path: Content-Disposition: inline In-Reply-To: <20131022153445.GD17512-HVbc7XotTAhnXn40ka+A6Q@public.gmane.org> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Jean-Christophe PLAGNIOL-VILLARD Cc: Denis Carikli , Mark Rutland , devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Ian Campbell , Eric B??nard , Pawel Moll , Stephen Warren , Jingoo Han , Rob Herring , Richard Purdie , Laurent Pinchart , Sascha Hauer , linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, Lothar Wa??mann List-Id: devicetree@vger.kernel.org --1yeeQ81UyVL57Vl7 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable 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-VILL= ARD wrote: > > > On 11:13 Mon 21 Oct , Denis Carikli wrote: > > > > Cc: Richard Purdie > > > > Cc: Jingoo Han > > > > Cc: Laurent Pinchart > > > > Cc: Rob Herring > > > > Cc: Pawel Moll > > > > Cc: Mark Rutland > > > > Cc: Stephen Warren > > > > Cc: Ian Campbell > > > > Cc: devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org > > > > Cc: Sascha Hauer > > > > Cc: linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org > > > > Cc: Lothar Wa=C3=9Fmann > > > > Cc: Jean-Christophe Plagniol-Villard > > > > Cc: Eric B=C3=A9nard > > > > Signed-off-by: Denis Carikli > > > > --- > > > > ChangeLog v3->v4: > > > > - The default-brightness property is now optional, it defaults to 1= if not set. > > > by default we set OFF not ON > > >=20 > > > do not actiate driver or properti by default you can not known to con= sequence > > > on the hw > >=20 > > 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. >=20 > I'm sorry but the blacklight descibe in DT have nothing to do with the co= mmon > 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. > put on by default if wrong specially without the property define. Even pu= t it > on by default it wrong as the bootloader may have set it already for spla= sh > 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. > 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. Thierry --1yeeQ81UyVL57Vl7 Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (GNU/Linux) iQIcBAEBAgAGBQJSZtmlAAoJEN0jrNd/PrOhsoEQAI7auF9rHWH/ynqdebfwq+zS js5wwoKjA/HhFtI/Uf1z2gfg1OlWO36xUXgXEEs/Zuqj7INeqP7bvft+N5rjfDsP bYW3GK8bxBIF5tOUglNJXm6661j38mHtdggDgLYQtSPczN0V6D5zc5txO/tR7Jsq ypb5xos5WdaYx5MIBNWz4d1xAbug/PH4vjcyw8cej3SY32Ku2kRnfyifYwGa8vV1 udTvzU36+LBfjdpoLhVgXcjCkgfuXg167cCO2vlulLb77NnPALXCxVKhibJirSET qu7gxRPa7tYDcA9OjvMyj7BovcC877Swm+zDG8e00ehGAPB3j8L5cCyg2+r6nz2k jqbeuYnO21fgqNo62WYxFg0M80cnamfXgwU09s/i06nbRE4UI/esIbjNSqI3t4n+ IfV+gWkRXfYtvm/9QDN0VrmYbLZtNTp5bVBRkrOqpWljAPk8WCZaPgNLghHCLLl9 0919354m9Ig/QVxAFTMQeIgiv8GCxkLww1C85vwkq0trRX8Wc6nKRcCM28ldsk0U RZ0vB5T4XXUJKdOl+6Dt8Q6URHW/hqBum/07X7ldfMNFzHZVYEDwaXNS4Td+g+Mo to5c2HVaLzbsqXOmdVkeRZ9ZdexeHr1i3f/wnUpQyZrIKfk2cteD53qKtSq6GQ4H g1h+V4NvJSzJmTDjNH9Z =hScn -----END PGP SIGNATURE----- --1yeeQ81UyVL57Vl7-- -- 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