From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751932Ab1HQLXw (ORCPT ); Wed, 17 Aug 2011 07:23:52 -0400 Received: from moutng.kundenserver.de ([212.227.126.186]:53722 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751119Ab1HQLXr (ORCPT ); Wed, 17 Aug 2011 07:23:47 -0400 From: Arnd Bergmann To: Stephen Warren Subject: Re: [RFC PATCH v2 00/13] arm/tegra: Initialize GPIO & pinmux from DT Date: Wed, 17 Aug 2011 13:23:38 +0200 User-Agent: KMail/1.12.2 (Linux/2.6.35-22-generic; KDE/4.3.2; x86_64; ; ) Cc: Linus Walleij , Grant Likely , Colin Cross , Erik Gilling , Olof Johansson , Russell King , "devicetree-discuss@lists.ozlabs.org" , "linux-tegra@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , Belisko Marek , Jamie Iles , Shawn Guo , Sergei Shtylyov References: <1313440100-17131-1-git-send-email-swarren@nvidia.com> <201108161637.16620.arnd@arndb.de> <74CDBE0F657A3D45AFBB94109FB122FF04AEA25368@HQMAIL01.nvidia.com> In-Reply-To: <74CDBE0F657A3D45AFBB94109FB122FF04AEA25368@HQMAIL01.nvidia.com> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201108171323.38441.arnd@arndb.de> X-Provags-ID: V02:K0:XCmy56cr3AvzV9LmY+LVEjxdPSV9bCKOPAtfGnf0BOn TZDQQUL/P9v16HdKCyrC/SIacKqUG8rYpmcuC1tTdXGhuHU/9l AzLFI5Y/pESXW6dGKahsDMseIimuYTG7W9qXtpkEVxmDcQct2j 1vFyMaBsw8CD1Ngj5fewGjDKpe4mNBh9Rwa7jOhlEE6IWd6ORJ YW0HuKbTs8NEm7GjGpAmg== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@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