From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751769AbaJFHTS (ORCPT ); Mon, 6 Oct 2014 03:19:18 -0400 Received: from metis.ext.pengutronix.de ([92.198.50.35]:46274 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751585AbaJFHTP (ORCPT ); Mon, 6 Oct 2014 03:19:15 -0400 Date: Mon, 6 Oct 2014 09:18:41 +0200 From: Sascha Hauer To: Linus Walleij Cc: "Hongzhou.Yang" , Rob Herring , Matthias Brugger , srv_heupstream@mediatek.com, Sascha Hauer , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , Russell King , Grant Likely , Hongzhou Yang , "Joe.C" , Catalin Marinas , Vladimir Murzin , Ashwin Chaugule , "devicetree@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , dandan.he@mediatek.com Subject: Re: [PATCH v2 4/4] ARM: dts: mt8135: Add pinctrl node for mt8135. Message-ID: <20141006071841.GN4992@pengutronix.de> References: <1411443545-24951-1-git-send-email-srv_hongzhou.yang@mediatek.com> <1411443545-24951-5-git-send-email-srv_hongzhou.yang@mediatek.com> <20140924124044.GC4992@pengutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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: 08:27:23 up 25 days, 23:14, 64 users, load average: 0.05, 0.05, 0.05 User-Agent: Mutt/1.5.21 (2010-09-15) X-SA-Exim-Connect-IP: 2001:67c:670:100:1d::c0 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, Oct 02, 2014 at 04:02:58PM +0200, Linus Walleij wrote: > On Wed, Sep 24, 2014 at 2:40 PM, Sascha Hauer wrote: > > On Wed, Sep 24, 2014 at 01:23:09PM +0200, Linus Walleij wrote: > > >> I haven't got to reviewing the driver, but this looks just wrong. > >> > >> Have the magic numbers in the driver. > >> > >> Use strings to describe functions, not integers. > > > > Interrupts, clocks, gpios, dma channels, nearly everything in the device tree is > > arbitrarily numbered. Instead of "irq-i2c0" we have <0 36 IRQ_TYPE_LEVEL_HIGH> > > in the device tree. These numbers can be resolved efficiently in the > > driver by shifting them to get a bitmask or by adding them as offset to > > a register base. > > Why do you want to make pinctrl different? > > Because pin control is about combining groups of pins with > certain functions. > > > Thanks to the recently > > introduced defines in the device trees these numbers are not magic at > > all anymore. > > Yeah that is good but not what I'm after here. > > >> We need to move toward standardized device tree bindings > >> for this stuff, and that means using strings, not magic > >> numbers. > > > > Agreed for standardized device tree bindings, but not for using strings. > > What is the alternative? Device Tree is very much about strings, > as is shown by the pin config bindings. The alternative is to use numbers. The majority of SoCs have a bit field per pad which is used for muxing the pad to different functions. The natural way to describe this is a pair of numbers: . The pad number can normally be directly translated into a register offset and the function number to a value written to that register. This is true for most SoCs I know of and makes it very easy to generate code for and to prove for correctness of both the code and the device tree. 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 |