Re: [PATCH v2 04/17] media: v4l2-subdev: Allow releasing frame descriptors on return

[Sakari Ailus <sakari.ailus@linux.intel.com>]

Hi Frank,

Thanks for the review.

On Tue, May 19, 2026 at 05:34:37PM -0400, Frank Li wrote:
> On Mon, May 18, 2026 at 07:43:04PM +0300, Sakari Ailus wrote:
> > Use DEFINE_FREE() to allow using __free() to release frame descriptors
> > using v4l2_subdev_free_frame_desc().
> >
> > Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
> > ---
> >  include/media/v4l2-subdev.h | 9 +++++++++
> >  1 file changed, 9 insertions(+)
> >
> > diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
> > index e7127953ac22..c10ca3f5d979 100644
> > --- a/include/media/v4l2-subdev.h
> > +++ b/include/media/v4l2-subdev.h
> > @@ -1798,6 +1798,11 @@ int v4l2_subdev_get_frame_desc_passthrough(struct v4l2_subdev *sd,
> >   * for each frame descriptor obtained by calling this function using
> >   * v4l2_subdev_free_frame_desc().
> >   *
> > + * Use __free() to release the frame descriptor automatically::
> > + *
> > + *    struct v4l2_mbus_frame_desc *desc __free(v4l2_subdev_free_frame_desc) =
> > + *            v4l2_subdev_get_frame_desc(sd, pad, desc);
> > + *
> 
> Generally, _get*()/_put*() is well known resource manage pair function
>            _alloc()/_free() is pair.
>            _request/_free()
> 
> Is it a little better v4l2_subdev_request_frame_desc() since get()/put() means
> have ref number?

We have similar v4l2_subdev_get_* calls that obtain various things like the
mbus format or selections, and that naming isn't aligned with get/put
either. I'm not entirely happy with the existing naming but changing it
would be a major amount of work for little gain. Either way, it still
aligns well with v4l2_subdev_get_frame_desc().

In fact I called the function v4l2_subdev_alloc_frame_desc() earlier but
changed the name as its main function is to obtain the frame descriptor by
using various means, not so much the allocation.

There will about ten users of the function albeit it'll grow slowly over
time.

-- 
Kind regards,

Sakari Ailus