From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752757Ab2GEGrs (ORCPT ); Thu, 5 Jul 2012 02:47:48 -0400 Received: from metis.ext.pengutronix.de ([92.198.50.35]:41322 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752539Ab2GEGrr (ORCPT ); Thu, 5 Jul 2012 02:47:47 -0400 Date: Thu, 5 Jul 2012 08:47:42 +0200 From: Sascha Hauer To: Alex Courbot Cc: Mark Brown , Thierry Reding , "linux-tegra@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-fbdev@vger.kernel.org" Subject: Re: [PATCH] pwm-backlight: add regulator and GPIO support Message-ID: <20120705064742.GL30009@pengutronix.de> References: <1340976167-27298-1-git-send-email-acourbot@nvidia.com> <20120704104840.GJ24458@pengutronix.de> <4FF43692.2040805@nvidia.com> <20120704130056.GC30009@pengutronix.de> <4FF45DDF.9000306@nvidia.com> <20120704152451.GA7333@sirena.org.uk> <4FF4FDC0.8020405@nvidia.com> <20120705062011.GI30009@pengutronix.de> <4FF53368.6090805@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4FF53368.6090805@nvidia.com> X-Sent-From: Pengutronix Hildesheim X-URL: http://www.pengutronix.de/ X-IRC: #ptxdist @freenode X-Accept-Language: de,en X-Accept-Content-Type: text/plain X-Uptime: 08:26:09 up 11 days, 21:37, 35 users, load average: 0.10, 0.09, 0.16 User-Agent: Mutt/1.5.21 (2010-09-15) X-SA-Exim-Connect-IP: 2001:6f8:1178:2:21e:67ff:fe11:9c5c X-SA-Exim-Mail-From: sha@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 05, 2012 at 03:25:44PM +0900, Alex Courbot wrote: > On 07/05/2012 03:20 PM, Sascha Hauer wrote: > >>Oh, that is a mistake of mine then. Driver probe should continue if > >>no regulator is declared (but should fail if some other error > >>occured). I want to maintain backward compatibility with current > >>users of the driver, so regulator/gpio specification should be > >>optional. > > > >I think the only way doing this is to add a flag to platform_data. I > >don't know if that's accepted though. > > I thought about just checking if devm_get_regulator returned -ENODEV > and happily continue if that was the case, assuming no regulator was > declared. And that's the problem. The get_regulator won't return -ENODEV. It will return -EPROBE_DEFER which tells you nothing about whether a regulator will ever be available or not. Having a flag in platform data would be fine with me, but I know other people think differently. BTW in devicetree this flag implicitely exists with the power-supply property. The regulator core could look if a power-supply property is given and - if it is given, a regulator is mandatory and the core either returns the regulator or -EPROBE_DEFER if it cannot find one. - If it is not given, there is no regulator and the core could either return a special error code or a dummy regulator. Right now the regulator core will just return -EPROBE_DEFER in both cases. This could easily be changed in the regulator core. Sascha -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |