Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932787AbcC3JQK (ORCPT ); Wed, 30 Mar 2016 05:16:10 -0400 Received: from bh-25.webhostbox.net ([208.91.199.152]:42723 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932510AbcC3JQH (ORCPT ); Wed, 30 Mar 2016 05:16:07 -0400 Subject: Re: [PATCH] gpio: Do not accept gpio chip additions before gpiolib initialization To: Alexandre Courbot References: <1459275638-11717-1-git-send-email-linux@roeck-us.net> Cc: Linus Walleij , "linux-gpio@vger.kernel.org" , Linux Kernel Mailing List From: Guenter Roeck Message-ID: <56FB9952.1030503@roeck-us.net> Date: Wed, 30 Mar 2016 02:16:02 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-Authenticated_sender: linux@roeck-us.net X-OutGoing-Spam-Status: No, score=-1.0 X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - bh-25.webhostbox.net X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - roeck-us.net X-Get-Message-Sender-Via: bh-25.webhostbox.net: authenticated_id: linux@roeck-us.net X-Authenticated-Sender: bh-25.webhostbox.net: linux@roeck-us.net X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1166 Lines: 24 On 03/30/2016 01:37 AM, Alexandre Courbot wrote: > On Wed, Mar 30, 2016 at 3:20 AM, Guenter Roeck wrote: >> Since commit ff2b13592299 ("gpio: make the gpiochip a real device"), >> attempts to add a gpio chip prior to gpiolib initialization cause the >> system to crash. Dump a warning to the console and return an error >> if the situation is encountered. > > Mmm I see the problem but this could seriously delay the availability > of some GPIOs that are useful for early system boot. > > I have not followed the GPIO device patches as closely as I should > have, but shouldn't you be able to register a GPIO chip without > immediately presenting it to user-space, for internal kernel needs? If > gpiolib is not initialized, then device-related operations would be > skipped, and gpiolib_dev_init() could then parse the list of > registered chips and fix them up when it gets called. > > Again, I'm speaking without real knowledge here, but that pattern > seems more resilent to me. > You are absolutely right, but my knowledge of gpiolib is not good enough to make that change. See this as a band-gap; it is better than just crashing. Guenter