linux-kernel - Re: [PATCH] drm/msm: Initialize mode

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Date:   Fri, 13 Jan 2023 10:57:18 +0200
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Bjorn Andersson <quic_bjorande@...cinc.com>,
        Rob Clark <robdclark@...il.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Johan Hovold <johan@...nel.org>
Cc:     Sean Paul <sean@...rly.run>, David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>, linux-arm-msm@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/msm: Initialize mode_config earlier

On 13/01/2023 06:23, Dmitry Baryshkov wrote:
> On 13/01/2023 06:10, Bjorn Andersson wrote:
>> Invoking drm_bridge_hpd_notify() on a drm_bridge with a HPD-enabled
>> bridge_connector ends up in drm_bridge_connector_hpd_cb() calling
>> drm_kms_helper_hotplug_event(), which assumes that the associated
>> drm_device's mode_config.funcs is a valid pointer.
>>
>> But in the MSM DisplayPort driver the HPD enablement happens at bind
>> time and mode_config.funcs is initialized late in msm_drm_init(). This
>> means that there's a window for hot plug events to dereference a NULL
>> mode_config.funcs.
>>
>> Move the assignment of mode_config.funcs before the bind, to avoid this
>> scenario.
> 
> Cam we make DP driver not to report HPD events until the enable_hpd() 
> was called? I think this is what was fixed by your internal_hpd patchset.

Or to express this in another words: I thought that internal_hpd already 
deferred enabling hpd event reporting till the time when we need it, 
didn't it?


-- 
With best wishes
Dmitry