From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [RFC PATCH v2 00/13] arm/tegra: Initialize GPIO & pinmux from DT Date: Wed, 17 Aug 2011 13:23:38 +0200 Message-ID: <201108171323.38441.arnd@arndb.de> References: <1313440100-17131-1-git-send-email-swarren@nvidia.com> <201108161637.16620.arnd@arndb.de> <74CDBE0F657A3D45AFBB94109FB122FF04AEA25368@HQMAIL01.nvidia.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <74CDBE0F657A3D45AFBB94109FB122FF04AEA25368-C7FfzLzN0UxDw2glCA4ptUEOCMrvLtNR@public.gmane.org> Sender: linux-tegra-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Stephen Warren Cc: Linus Walleij , Grant Likely , Colin Cross , Erik Gilling , Olof Johansson , Russell King , "devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org" , "linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Belisko Marek , Jamie Iles , Shawn Guo , Sergei Shtylyov List-Id: linux-tegra@vger.kernel.org On Tuesday 16 August 2011, Stephen Warren wrote: > One issue here: There isn't always a single gpio/pinmux parent; as a > concrete example, the ALSA/ASoC driver for Tegra+WM8903 uses GPIOs both > from Tegra itself, and from the WM8903 audio codec. > > I could imagine the same being true in basically any case where one > device uses N GPIOs (e.g. SD controller with power, change-detect, > and read-only GPIOs; some could easily come from the SoC and some > from a GPIO expander). > > I'm not quite so sure that multiple parents would be useful for pinmux, > but I wouldn't say that it was impossible... Hmm, how common do you think the example is? It it's just a very rare case, we can still special-case it by introducing fake subdevices for the Tegra+WM8903 driver, each of which has only one gpio-parent. This is ugly but keeps the special case to the rare devices. If we can expect more than a handful of these, we probably need a better design for the binding, which will cause a burden for all drivers. Arnd