linux-kernel - Re: [PATCH 1/7] drm/bridge: Support hotplugging panel-bridge.

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Message-ID: <871sqkouvr.fsf@eliezer.anholt.net>
Date:   Fri, 16 Jun 2017 07:43:52 -0700
From:   Eric Anholt <eric@...olt.net>
To:     Archit Taneja <architt@...eaurora.org>,
        dri-devel@...ts.freedesktop.org,
        Andrzej Hajda <a.hajda@...sung.com>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>, devicetree@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/7] drm/bridge: Support hotplugging panel-bridge.

Archit Taneja <architt@...eaurora.org> 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().

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