[PATCH v1] drm/vkms: Add writeback encoders as possible clones

[Robert Mader]

Thanks for the feedback!

On 06.07.25 13:29, Dmitry Baryshkov wrote:
> On Thu, Jul 03, 2025 at 11:03:35AM +0200, Robert Mader wrote:
>> Since commit 41b4b11da0215 ("drm: Add valid clones check") setting
>> the `possible_clones` values is a hard requirement for cloning.
>> `vkms` supports cloning for writeback connectors in order to capture
>> CRTC content, however that broke with said commit.
>>
>> Writeback connectors are created on a per-CRTC basis, thus mark
>> every non-writeback connector that is compatible with a given CRTC
>> as possible clone - and vice-versa.
>>
>> Using a default configuration, the corresponding `drm_info` output
>> changes from:
> It feels like the current possible_clones is incorrect according to the
> documentation. Should there be a Fixes tag?

The issue is that possible_clones was never explicitly set, making it 
fall back to the default value - every encoder only being compatible 
with itself. So candidates for a Fixes tag would be either the initial 
implementation of the writeback connector in vkms - or the commit that 
started enforcing correct values ("drm: Add valid clones check") as 
previously the values where simply ignored.

Unfortunately the patch is not easily backportable either way because of 
the changes in https://patchwork.freedesktop.org/series/144091/#rev4 
that recently landed - i.e. 6.15 would need a completely rewritten fix, 
and previous kernels don't really need it.

Thus I'd rather leave it out if that's ok with you?

>>
>> Signed-off-by: Robert Mader<robert.mader at collabora.com>
>> ---
>>   drivers/gpu/drm/vkms/vkms_output.c    | 12 ++++++++++++
>>   drivers/gpu/drm/vkms/vkms_writeback.c |  2 ++
>>   2 files changed, 14 insertions(+)
>>
-- 
Robert Mader
Consultant Software Developer

Collabora Ltd.
Platinum Building, St John's Innovation Park, Cambridge CB4 0DS, UK
Registered in England & Wales, no. 5513718
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.freedesktop.org/archives/dri-devel/attachments/20250718/6f4b5fdd/attachment.htm>