From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bob Feretich Subject: Re: Another problem with I2C multiplexer bus naming - solved Date: Thu, 12 Mar 2015 11:49:48 -0700 Message-ID: <5501DFCC.6010408@rafresearch.com> References: <1426133507.16219.YahooMailNeo@web181502.mail.ne1.yahoo.com> <1426136151.37151.YahooMailNeo@web181506.mail.ne1.yahoo.com> <20150312094423.GB4225@katana> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20150312094423.GB4225@katana> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Wolfram Sang Cc: "linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Guenter Roeck List-Id: linux-i2c@vger.kernel.org On 3/12/2015 2:44 AM, Wolfram Sang wrote: > On Wed, Mar 11, 2015 at 09:55:51PM -0700, Bob Feretich wrote: > >> I tried some random things and setting aliases in the dtsi file solved >> the problem. > > Good. > >> The use of an alias to set the name of an i2c bus should >> be documented somewhere! > > Well, send a patch adding some documentation where you would have liked > to see it. > > Thanks, > > Wolfram > The first two places I looked for information were: * https://www.kernel.org/doc/Documentation/devicetree/bindings/i2c/i2c-mux.txt This is where I found the info on specifying the multiplexer without aliases. It would seem logical to add the description of "how to explicitly name child buses" here. * https://www.kernel.org/doc/Documentation/i2c/muxes/i2c-mux-gpio Even though this file is for gpio controlled multiplexers, it seemed like a good spot to look for information on how to specify i2c multiplexers in general. It only describes the board.c method of registering adapters. (I don't know which gpio_i2cmux_platform_data fields would be the equivalent of specifying the device tree aliases.) Perhaps a cross-reference to the above documentation is appropriate, since use of customized board.c files is being discouraged. Note that once device trees become dynamic and support hot plugging, the alias bus naming solution becomes ineffective, unless there is a way to specify a hierarchical alias that references the bus/adapter id of the multiplexer. Thanks, Bob