From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from avon.wwwdotorg.org ([70.85.31.133]:41714 "EHLO avon.wwwdotorg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758294Ab3BHXV1 (ORCPT ); Fri, 8 Feb 2013 18:21:27 -0500 Message-ID: <51158873.3060508@wwwdotorg.org> Date: Fri, 08 Feb 2013 16:21:23 -0700 From: Stephen Warren MIME-Version: 1.0 To: Sylwester Nawrocki CC: Sylwester Nawrocki , linux-media@vger.kernel.org, kyungmin.park@samsung.com, kgene.kim@samsung.com, rob.herring@calxeda.com, prabhakar.lad@ti.com, devicetree-discuss@lists.ozlabs.org, linux-samsung-soc@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v4 02/10] s5p-fimc: Add device tree support for FIMC devices References: <1359745771-23684-1-git-send-email-s.nawrocki@samsung.com> <1359745771-23684-3-git-send-email-s.nawrocki@samsung.com> <5112E9EF.8090908@wwwdotorg.org> <5115874A.6050406@gmail.com> In-Reply-To: <5115874A.6050406@gmail.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-media-owner@vger.kernel.org List-ID: On 02/08/2013 04:16 PM, Sylwester Nawrocki wrote: > On 02/07/2013 12:40 AM, Stephen Warren wrote: >>> diff --git >>> a/Documentation/devicetree/bindings/media/soc/samsung-fimc.txt >>> b/Documentation/devicetree/bindings/media/soc/samsung-fimc.txt >> >>> +Samsung S5P/EXYNOS SoC Camera Subsystem (FIMC) >>> +---------------------------------------------- ... >>> +For every fimc node a numbered alias should be present in the >>> aliases node. >>> +Aliases are of the form fimc, where is an integer (0...N) >>> specifying >>> +the IP's instance index. >> >> Why? Isn't it up to the DT author whether they care if each fimc node is >> assigned a specific identification v.s. whether identification is >> assigned automatically? > > There are at least three different kinds of IPs that come in multiple > instances in an SoC. To activate data links between them each instance > needs to be clearly identified. There are also differences between > instances of same device. Hence it's important these aliases don't have > random values. > > Some more details about the SoC can be found at [1]. The aliases are > also already used in the Exynos5 GScaler bindings [2] in a similar way. Hmmm. I'd expect explicit DT properties to represent the instance-specific "configuration", or even different compatible values. Relying on the alias ID seems rather indirect; what if in e.g. Exynos6/... the mapping from instance/alias ID to feature set changes. With explicit DT properties, that'd just be a .dts change, whereas by requiring alias IDs now, you'd need a driver change to support this.