linux-kernel - Re: [PATCH v3] media: v4l2-ctrls: add full AV1 profile validation in validate_av1

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Message-ID: <CAKPKb88VHwGp-iLMa=zZy3Czq8S8wUd9Zzkicvd4er9OiLg6UQ@mail.gmail.com>
Date: Tue, 7 Oct 2025 16:20:54 +0530
From: opensource india <opensource206@...il.com>
To: Daniel Almeida <daniel.almeida@...labora.com>
Cc: mchehab@...nel.org, hverkuil@...nel.org, ribalda@...omium.org, 
	laurent.pinchart@...asonboard.com, yunkec@...gle.com, 
	sakari.ailus@...ux.intel.com, james.cowgill@...ize.com, hansg@...nel.org, 
	linux-kernel@...r.kernel.org, linux-media@...r.kernel.org
Subject: Re: [PATCH v3] media: v4l2-ctrls: add full AV1 profile validation in validate_av1_sequence()

On Sat, Sep 27, 2025 at 2:27 PM Daniel Almeida
<daniel.almeida@...labora.com> wrote:
>
> Hi, I’ll review this in the coming weeks.

Hi Daneil, did you get a chance to review this?

> > On 27 Sep 2025, at 06:51, opensource india <opensource206@...il.com> wrote:
> >
> > On Sat, Sep 13, 2025 at 4:23 PM Pavan Bobba <opensource206@...il.com> 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.
>
> Mauro,
>
> A reminder that I have been warning about this for quite a while [0], which
> includes mentioning that patches like this, although welcome, do not solve the
> root issue completely.
>
> I keep working on what I believe to be the solution [1][2]. I would appreciate if
> we could restart this discussion.
>
> [0]: https://lwn.net/Articles/970565/
> [1]: https://lore.kernel.org/linux-media/20250818-v4l2-v1-0-6887e772aac2@collabora.com/
> [2]: https://lwn.net/Articles/963966/
>