linux-kernel - Re: [PATCH v6 11/18] drm/display: bridge_connector: Ensure last bridge determines EDID/modes detection capabilities

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Message-ID: <600da5e2-da28-429b-ba7a-6ddabeeb044d@rock-chips.com>
Date: Thu, 9 Oct 2025 11:15:13 +0800
From: Damon Ding <damon.ding@...k-chips.com>
To: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
Cc: andrzej.hajda@...el.com, neil.armstrong@...aro.org, rfoss@...nel.org,
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Subject: Re: [PATCH v6 11/18] drm/display: bridge_connector: Ensure last
 bridge determines EDID/modes detection capabilities

Hi Dmitry,

On 10/1/2025 4:21 AM, Dmitry Baryshkov wrote:
> On Tue, Sep 30, 2025 at 05:09:13PM +0800, Damon Ding wrote:
>> When multiple bridges are present, EDID detection capability
>> (DRM_BRIDGE_OP_EDID) takes precedence over modes detection
>> (DRM_BRIDGE_OP_MODES). To ensure the above two capabilities are
>> determined by the last bridge in the chain, we handle three cases:
>>
>> Case 1: The later bridge declares only DRM_BRIDGE_OP_MODES
>>   - If the previous bridge declares DRM_BRIDGE_OP_EDID, set
>>     &drm_bridge_connector.bridge_edid to NULL and set
>>     &drm_bridge_connector.bridge_modes to the later bridge.
>>   - Ensure modes detection capability of the later bridge will not
>>     be ignored.
>>
>> Case 2: The later bridge declares only DRM_BRIDGE_OP_EDID
>>   - If the previous bridge declares DRM_BRIDGE_OP_MODES, set
>>     &drm_bridge_connector.bridge_modes to NULL and set
>>     &drm_bridge_connector.bridge_edid to the later bridge.
>>   - Although EDID detection capability has higher priority, this
>>     operation is for balance and makes sense.
>>
>> Case 3: the later bridge declares both of them
>>   - Assign later bridge as &drm_bridge_connector.bridge_edid and
>>     and &drm_bridge_connector.bridge_modes to this bridge.
>>   - Just leave transfer of these two capabilities as before.
>>
>> Signed-off-by: Damon Ding <damon.ding@...k-chips.com>
>> Suggested-by: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
>> ---
>>   .../gpu/drm/display/drm_bridge_connector.c    | 42 +++++++++++++++++++
>>   1 file changed, 42 insertions(+)
>>
> 
> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
> 
> But I'd suggest pulling this to a top of the series to let others also
> take a look at it.
> 

Will do in v7.

Best regards,
Damon