Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751458AbdFTDsJ (ORCPT ); Mon, 19 Jun 2017 23:48:09 -0400 Received: from smtp.codeaurora.org ([198.145.29.96]:53310 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750979AbdFTDsG (ORCPT ); Mon, 19 Jun 2017 23:48:06 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org EAA5660AC8 Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=none smtp.mailfrom=architt@codeaurora.org Subject: Re: [PATCH 1/7] drm/bridge: Support hotplugging panel-bridge. To: Eric Anholt , dri-devel@lists.freedesktop.org, Andrzej Hajda , Laurent Pinchart , Thierry Reding , Rob Herring , Mark Rutland , devicetree@vger.kernel.org Cc: linux-kernel@vger.kernel.org References: <20170615204130.19255-1-eric@anholt.net> <20170615204130.19255-2-eric@anholt.net> <777ee1b1-e5ce-ea29-8a48-f792354a22d1@codeaurora.org> <871sqkouvr.fsf@eliezer.anholt.net> From: Archit Taneja Message-ID: <8e148170-b626-b426-3c94-b93d2746f4ce@codeaurora.org> Date: Tue, 20 Jun 2017 09:18:00 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.1.1 MIME-Version: 1.0 In-Reply-To: <871sqkouvr.fsf@eliezer.anholt.net> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1696 Lines: 41 On 06/16/2017 08:13 PM, Eric Anholt wrote: > Archit Taneja writes: > >> On 06/16/2017 02:11 AM, Eric Anholt wrote: >>> If the panel-bridge is being set up after the drm_mode_config_reset(), >>> then the connector's state would never get initialized, and we'd >>> dereference the NULL in the hotplug path. We also need to register >>> the connector, so that userspace can get at it. >>> >> >> Shouldn't the KMS driver make sure the panel-bridge is set up before >> drm_mode_config_reset? Is it the case when we're inserting the >> panel-bridge driver as a module? >> >> >> All the connectors that have been added are registered automatically >> when drm_dev_register() is called by the KMS driver. Registering a >> connector in the middle of setting up our driver is prone to race >> conditions if the userspace decides to use them immediately. > > Yeah, this is fixing initializing panel_bridge at DSI host_attach time, > which in the case of a panel module that creates the DSI device > (adv7533-style, like you said I should use as a reference) will be after > drm_mode_config_reset() and drm_dev_register(). Okay. In the case of the msm kms driver, we defer probe until the adv7533 module is inserted, only then we proceed to drm_mode_config_reset() and drm_dev_register(). I assumed this was the general practice followed by most kms drivers. I.,e the kms driver defers probe until all connector related modules are inserted, and only then proceed to create a drm device. Feedback from others on this would be appreciated, though. Thanks, Archit -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project