Re: [PATCH] drm/displayid: fix Tiled Display Topology ID size

[Jani Nikula <jani.nikula@intel.com>]

On Thu, 11 Jun 2026, David Airlie <airlied@redhat.com> wrote:
> On Thu, Jun 11, 2026 at 12:16 AM Jani Nikula <jani.nikula@intel.com> wrote:
>>
>> The Tiled Display Topology ID of a DisplayID Tiled Display Topology Data
>> Block consists of three fields:
>>
>> - Tiled Display Manufacturer/Vendor ID Field (3 bytes)
>> - Tiled Display Product ID Code Field (2 bytes)
>> - Tiled Display Serial Number Field (4 bytes)
>>
>> i.e. a total of 9 bytes, not 8.
>>
>> The DisplayID Tiled Display Topology ID is used as the tile group
>> identifier.
>>
>> Update both struct displayid_tiled_block topology_id member and struct
>> drm_tile_group group_data member to full 9 bytes.
>>
>> The group data was missing the last byte of the serial number. I don't
>> know whether there are known bug reports that might be linked to this,
>> but it's plausible the last byte could be the differentiating part for
>> the tile groups, and fewer tile groups might have been created than
>> intended.
>
> I pulled out my spec, and indeed I can confirm this is the correct reading!
>
> Reviewed-by: Dave Airlie <airlied@redhat.com>

Thanks for the review, pushed to drm-misc-fixes.

BR,
Jani.


-- 
Jani Nikula, Intel