Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935025AbcKWKGW (ORCPT ); Wed, 23 Nov 2016 05:06:22 -0500 Received: from foss.arm.com ([217.140.101.70]:47376 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934196AbcKWKFa (ORCPT ); Wed, 23 Nov 2016 05:05:30 -0500 Subject: Re: [PATCH 1/3] of: base: add support to get machine compatible string To: Sekhar Nori References: <1479811311-3080-1-git-send-email-bgolaszewski@baylibre.com> <1479811311-3080-2-git-send-email-bgolaszewski@baylibre.com> <5ce9fb9f-459a-562b-2e9f-85d35f9ec035@arm.com> <67a3c2c7-0cb9-9764-2710-6ee66fc4dde4@ti.com> Cc: Bartosz Golaszewski , Kevin Hilman , Michael Turquette , Rob Herring , Frank Rowand , Mark Rutland , Peter Ujfalusi , Russell King , Sudeep Holla , LKML , arm-soc , linux-drm , linux-devicetree , Jyri Sarha , Tomi Valkeinen , David Airlie , Laurent Pinchart , Robin Murphy From: Sudeep Holla Organization: ARM Message-ID: <2a644b8c-d91e-5ab1-200b-00f749a36307@arm.com> Date: Wed, 23 Nov 2016 10:05:24 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1761 Lines: 57 On 23/11/16 07:49, Sekhar Nori wrote: > On Tuesday 22 November 2016 09:16 PM, Sudeep Holla wrote: >> Hi Sekhar, >> >> On 22/11/16 15:06, Sekhar Nori wrote: >>> Hi Sudeep, >>> >>> On Tuesday 22 November 2016 04:23 PM, Sudeep Holla wrote: >>>> >>>> >>>> On 22/11/16 10:41, Bartosz Golaszewski wrote: >>>>> Add a function allowing to retrieve the compatible string of the root >>>>> node of the device tree. >>>>> >>>> >>>> Rob has queued [1] and it's in -next today. You can reuse that if you >>>> are planning to target this for v4.11 or just use open coding in your >>>> driver for v4.10 and target this move for v4.11 to avoid cross tree >>>> dependencies as I already mentioned in your previous thread. >>> >>> I dont have your original patch in my mailbox, but I wonder if >>> returning a pointer to property string for a node whose reference has >>> already been released is safe to do? Probably not an issue for the root >>> node, but still feels counter-intuitive. >>> >> >> I am not sure if I understand the issue here. Are you referring a case >> where of_root is freed ? > > Yes, right, thats what I was hinting at. Since you are giving up the > reference to the device node before the function returns, the user can > be left with a dangling reference. > Yes I agree. >> Also I have seen drivers today just using this pointer directly, but >> it's better to copy the string(I just saw this done in one case) > > Hmm, the reference is given up before the API returns, so I doubt > copying it later is any additional benefit. > True. > I suspect this is a theoretical issue though since root device node is > probably never freed. > Indeed, not sure if it's worth adding additional code to release the nod at all call sites. -- Regards, Sudeep