From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753866AbaKME3E (ORCPT ); Wed, 12 Nov 2014 23:29:04 -0500 Received: from mail-la0-f52.google.com ([209.85.215.52]:39276 "EHLO mail-la0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753629AbaKME27 (ORCPT ); Wed, 12 Nov 2014 23:28:59 -0500 Message-ID: <54643384.5030309@gmail.com> Date: Wed, 12 Nov 2014 20:28:52 -0800 From: Frank Rowand Reply-To: frowand.list@gmail.com User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:17.0) Gecko/20130801 Thunderbird/17.0.8 MIME-Version: 1.0 To: Benjamin Herrenschmidt CC: devicetree@vger.kernel.org, "linux-kernel@vger.kernel.org" , Rob Herring , Arnd Bergmann Subject: Re: [RFC] Add of_path property for all devices with a node References: <1415342031.4925.27.camel@kernel.crashing.org> In-Reply-To: <1415342031.4925.27.camel@kernel.crashing.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/6/2014 10:33 PM, Benjamin Herrenschmidt wrote: > Hey folks ! This is not (yet) a formal patch submission but... > > So I've been annoyed lately with having a bunch of devices such as i2c > eeproms (for use by VPDs, server world !) and other bits and pieces that > I want to be able to identify from userspace, and possibly provide > additional data about from FW. > > Basically, it boils down to correlating the sysfs device with the OF > tree device node, so that user space can use device-tree info such as > additional "location" or "label" (or whatever else we can come up with) > propreties to identify a given device, or get some attributes of use > about it, etc... > > Now, so far, we've done that in some subsystem in a fairly ad-hoc basis > using "devspec" properties. For example, PCI creates them if it can > correlate the probed device with a DT node. Some powerpc specific busses > do that too. > > However, i2c doesn't and it would be nice to have something more generic > since technically any device can have a corresponding device tree node. > > So I came up with this patch, it seems to work well for me. I'm adding > an "of_path" attribute to not conflict with the existing "devspec" one > just for the sake of this experiment (plus "devspec" sucks). Long run, > we might want to use of_path and leave a "devspec" symlink to of_path on > the few busses that currently have devspec (pci and some powerpc > specific ones). > > Comments ? > > Cheers, > Ben. If I understand correctly, that information is already available in the file uevent. For example, if I apply your patch, at least for a simple path, I see the same path name in uevent as in of_path: $ cd /sys/devices/soc/f9824900.sdhci $ cat of_path /soc/sdhci@f9824900 $ grep OF_FULLNAME uevent | cut -d"=" -f2 /soc/sdhci@f9824900 -Frank