Re: [PATCH REGRESSION] drm/panel: simple: restore connector_type fallback

[<Ludovic.Desroches@microchip.com>]

On 11/21/25 23:52, Dmitry Baryshkov wrote:
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> 
> On Fri, Nov 21, 2025 at 02:20:48PM +0100, Ludovic Desroches wrote:
>> The switch from devm_kzalloc() + drm_panel_init() to
>> devm_drm_panel_alloc() introduced a regression.
>>
>> Several panel descriptors do not set connector_type. For those panels,
>> panel_simple_probe() used to compute a connector type (currently DPI as a
>> fallback) and pass that value to drm_panel_init(). After the conversion
>> to devm_drm_panel_alloc(), the call unconditionally used
>> desc->connector_type instead, ignoring the computed fallback and
>> potentially passing DRM_MODE_CONNECTOR_Unknown, which
>> drm_panel_bridge_add() does not allow.
>>
>> Move the connector_type validation / fallback logic before the
>> devm_drm_panel_alloc() call and pass the computed connector_type to
>> devm_drm_panel_alloc(), so panels without an explicit connector_type
>> once again get the DPI default.
>>
>> Signed-off-by: Ludovic Desroches <ludovic.desroches@microchip.com>
>> Fixes: de04bb0089a9 ("drm/panel/panel-simple: Use the new allocation in place of devm_kzalloc()")
>> ---
>> Hi,
>>
>> I am not sure whether this regression has already been reported or
>> addressed. If it has, please feel free to drop this patch.
> 
> Would it be better to fix those panels instead? In the end, the panel
> usually has only one bus.

I don’t have a strong opinion on this point. I don’t know if there are 
any historical reasons behind all this.

Regards,
Ludovic

> 
>> ---
>>   drivers/gpu/drm/panel/panel-simple.c | 86 ++++++++++++++++++------------------
>>   1 file changed, 43 insertions(+), 43 deletions(-)
> 
> --
> With best wishes
> Dmitry