Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752633AbdFVHuN (ORCPT ); Thu, 22 Jun 2017 03:50:13 -0400 Received: from mail-qt0-f175.google.com ([209.85.216.175]:36516 "EHLO mail-qt0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751124AbdFVHuL (ORCPT ); Thu, 22 Jun 2017 03:50:11 -0400 MIME-Version: 1.0 In-Reply-To: <871sqe7ei0.fsf@eliezer.anholt.net> 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> <8e148170-b626-b426-3c94-b93d2746f4ce@codeaurora.org> <871sqe7ei0.fsf@eliezer.anholt.net> From: Benjamin Gaignard Date: Thu, 22 Jun 2017 09:50:10 +0200 Message-ID: Subject: Re: [PATCH 1/7] drm/bridge: Support hotplugging panel-bridge. To: Eric Anholt Cc: Archit Taneja , "dri-devel@lists.freedesktop.org" , Andrzej Hajda , Laurent Pinchart , Thierry Reding , Rob Herring , Mark Rutland , devicetree@vger.kernel.org, Linux Kernel Mailing List , Philippe Cornu Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2482 Lines: 54 2017-06-20 19:31 GMT+02:00 Eric Anholt : > Archit Taneja writes: > >> 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. > > The problem, though, is the panel driver needs the MIPI DSI host to > exist to call mipi_dsi_device_register_full() during the probe process. > The adv7533 driver gets around this by registering the DSI device in the > bridge attach step, but drm_panel doesn't have an attach step. > > Another alternative is my original version of the panel driver that was > a mipi_dsi_device driver that registered the panel during the DSI device > probe. That's why vc4's panel lookup is during the MIPI DSI attach > phase, currently. + Philippe in copy because we have the same probing issue when adding panel-bridge with the dsi bridge > > _______________________________________________ > dri-devel mailing list > dri-devel@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/dri-devel >