Re: [PATCH v3] media: v4l2-ctrls: add full AV1 profile validation in validate_av1_sequence()

[Hans Verkuil <hverkuil+cisco@kernel.org>]

On 23/10/2025 12:32, opensource india wrote:
> On Wed, Oct 22, 2025 at 12:44 PM Hans Verkuil <hverkuil+cisco@kernel.org> wrote:
>>
>> Hi Pavan,
>>
>> On 13/09/2025 12:52, Pavan Bobba wrote:
>>> Complete the "TODO: PROFILES" by enforcing profile-specific and
>>> monochrome constraints as defined by the AV1 specification
>>> (Section 5.5.2, "Color config syntax").
>>>
>>> The validator now checks:
>>>
>>>  - Flags: reject any unknown bits set in sequence->flags
>>>  - Profile range: only profiles 0..2 are valid
>>>  - Profile 0: 8/10-bit only, subsampling must be 4:2:0 (sx=1, sy=1),
>>>    monochrome allowed
>>>  - Profile 1: 8/10-bit only, subsampling must be 4:4:4 (sx=0, sy=0),
>>>    monochrome forbidden
>>>  - Profile 2:
>>>     * 8/10-bit: only 4:2:2 allowed (sx=1, sy=0)
>>>     * 12-bit: 4:4:4 (sx=0, sy=0), 4:2:2 (sx=1, sy=0), or 4:2:0 (sx=1, sy=1)
>>>       allowed
>>>  - Monochrome path (all profiles except 1): forces subsampling_x=1,
>>>    subsampling_y=1, separate_uv_delta_q=0
>>>
>>> These checks prevent userspace from providing invalid AV1 sequence
>>> headers that would otherwise be accepted, leading to undefined driver
>>> or hardware behavior.
>>
>> This patch was merged in our media-committers next branch, but I noticed that
>> it now fails the v4l2-compliance test for the visl driver.
>>
>> The cause is that the new validation now fails with the default values for
>> this control as set in std_init_compound().
>>
>> You can test this yourself by loading the visl driver and then running
>> v4l2-compliance -d /dev/videoX -E --verbose
>> (-E stops at the first error)
>>
>> Can you provide a patch to initialize this control with sane values?
>>
>> Apologies for not noticing this before: there are some issues with the automatic
>> regression tests in our CI, so the tests weren't run.
>>
>> Regards,
>>
>>         Hans
>>
> 
> Hi Hans Verkuil,
> 
> Thank you so much for the review.
> yes, v4l2-compliance expected to fail indeed since it is sending
> default values which, our newly added code rejects as per
> specification
> 
> when you say patch, you mean patch for v4l2-compliance tool with
> proper values so that v4l2 core driver can accept?

No, std_init_compound() in the kernel needs to be patched so the initial
value of this control passes the new validation tests. The initial control
values should always be sane.

Regards,

	Hans