From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751677AbdBWXX0 (ORCPT ); Thu, 23 Feb 2017 18:23:26 -0500 Received: from mail-pg0-f66.google.com ([74.125.83.66]:36167 "EHLO mail-pg0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751422AbdBWXXX (ORCPT ); Thu, 23 Feb 2017 18:23:23 -0500 Subject: Re: [RFC/PATCH] of: Mark property::value as const To: Rob Herring References: <20170214025040.23955-1-stephen.boyd@linaro.org> <58AF3E06.4030701@gmail.com> <58AF4D03.7020908@gmail.com> Cc: Stephen Boyd , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "devicetree@vger.kernel.org" From: Frank Rowand Message-ID: <58AF6EE7.5050008@gmail.com> Date: Thu, 23 Feb 2017 15:23:19 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1 MIME-Version: 1.0 In-Reply-To: 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 02/23/17 14:09, Rob Herring wrote: > On Thu, Feb 23, 2017 at 2:58 PM, Frank Rowand wrote: >> On 02/23/17 11:54, Frank Rowand wrote: >>> On 02/13/17 18:50, Stephen Boyd wrote: >>>> The 'blob' we pass into populate_properties() is marked as const, >>>> but we cast that const away when we assign the result of >>>> fdt_getprop_by_offset() to pp->value. Let's mark value as const >>>> instead, so that code can't mistakenly write to the value of the >>>> property that we've so far advertised as const. >>>> >>>> Unfortunately, this exposes a problem with the fdt resolver code, >>>> where we overwrite the value member of properties of phandles to >>>> update them with their final value. Add a comment for now to >>>> indicate where we're potentially writing over const data. >>> >>> The resolver should not be over writing anything in the FDT. I'll >>> look at what is going on there. >>> >>> The FDT we expose to user space should be the FDT we booted with, >>> not something later modified. >> >> It seems that /sys/firmware/fdt is not documented. I'll look into >> fixing that. > > That's because the "official" interface is /proc/device-tree/ which is > now a symlink. IIRC, it is documented to use /proc/device-tree, not > the sysfs path. > > Rob > . > Documentation/ABI/testing/sysfs-firmware-ofw describes /sys/firmware/devicetree/* but not /sys/firmware/fdt It also describes the /proc/device-tree symlink to /sys/firmware/devicetree/base as the official stable ABI, as you mentioned. So it is just fdt that I have not found the documentation for. -Frank