Hi Hans,
On Thu, Apr 04, 2024 at 10:27:49AM +0200, Hans Verkuil wrote:
> Hi Laurent,
>
> On 04/04/2024 00:42, Laurent Pinchart wrote:
> > When support for streams was added to the V4L2 subdev API, the
> > v4l2_subdev_crop structure was extended with a stream field, but the
> > field was not handled in the core code that translates the
> > VIDIOC_SUBDEV_[GS]_CROP ioctls to the selection API. This could be
> > fixed, but the crop API is deprecated and shouldn't be used by new
> > userspace code. It's therefore best to avoid extending it with new
> > features. Drop the stream field from the v4l2_subdev_crop structure, and
> > update the documentation and kernel code accordingly.
> >
> > Fixes: 2f91e10ee6fd ("media: subdev: add stream based configuration")
> > Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> > ---
> > This supersedes the "[PATCH] media: v4l2-subdev: Fix stream handling for
> > crop API" patch ([1]). I'll submit matching patches for v4l2-compliance.
> >
> > [1] https://patchwork.linuxtv.org/project/linux-media/patch/20240401233725.2401-1-laurent.pinchart@xxxxxxxxxxxxxxxx/
> > ---
> > .../userspace-api/media/v4l/vidioc-subdev-g-crop.rst | 5 +----
> > drivers/media/v4l2-core/v4l2-subdev.c | 6 ------
> > include/uapi/linux/v4l2-subdev.h | 4 +---
> > 3 files changed, 2 insertions(+), 13 deletions(-)
> >
> > diff --git a/Documentation/userspace-api/media/v4l/vidioc-subdev-g-crop.rst b/Documentation/userspace-api/media/v4l/vidioc-subdev-g-crop.rst
> > index 92d933631fda..7eeb7b553abf 100644
> > --- a/Documentation/userspace-api/media/v4l/vidioc-subdev-g-crop.rst
> > +++ b/Documentation/userspace-api/media/v4l/vidioc-subdev-g-crop.rst
> > @@ -96,10 +96,7 @@ modified format should be as close as possible to the original request.
> > - ``rect``
> > - Crop rectangle boundaries, in pixels.
> > * - __u32
> > - - ``stream``
> > - - Stream identifier.
> > - * - __u32
> > - - ``reserved``\ [7]
> > + - ``reserved``\ [8]
> > - Reserved for future extensions. Applications and drivers must set
> > the array to zero.
> >
> > diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
> > index 4c6198c48dd6..02c2a2b472df 100644
> > --- a/drivers/media/v4l2-core/v4l2-subdev.c
> > +++ b/drivers/media/v4l2-core/v4l2-subdev.c
> > @@ -725,9 +725,6 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg,
> > struct v4l2_subdev_crop *crop = arg;
> > struct v4l2_subdev_selection sel;
> >
> > - if (!client_supports_streams)
> > - crop->stream = 0;
> > -
> > memset(crop->reserved, 0, sizeof(crop->reserved));
> > memset(&sel, 0, sizeof(sel));
> > sel.which = crop->which;
> > @@ -749,9 +746,6 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg,
> > if (crop->which != V4L2_SUBDEV_FORMAT_TRY && ro_subdev)
> > return -EPERM;
> >
> > - if (!client_supports_streams)
> > - crop->stream = 0;
> > -
> > memset(crop->reserved, 0, sizeof(crop->reserved));
> > memset(&sel, 0, sizeof(sel));
> > sel.which = crop->which;
> > diff --git a/include/uapi/linux/v4l2-subdev.h b/include/uapi/linux/v4l2-subdev.h
> > index 7048c51581c6..f7eea12d8a2c 100644
> > --- a/include/uapi/linux/v4l2-subdev.h
> > +++ b/include/uapi/linux/v4l2-subdev.h
> > @@ -48,15 +48,13 @@ struct v4l2_subdev_format {
> > * @which: format type (from enum v4l2_subdev_format_whence)
> > * @pad: pad number, as reported by the media API
> > * @rect: pad crop rectangle boundaries
> > - * @stream: stream number, defined in subdev routing
> > * @reserved: drivers and applications must zero this array
> > */
> > struct v4l2_subdev_crop {
> > __u32 which;
> > __u32 pad;
> > struct v4l2_rect rect;
> > - __u32 stream;
> > - __u32 reserved[7];
> > + __u32 reserved[8];
> > };
>
> Sorry, but you can't remove this field. This field has been in the uAPI since
> v6.3, and applications might be using it, even if only to set it to 0. Removing
> this field will break compilation of such applications.
>
> Just fix the stream support instead, rather than removing it, as you did in
> your original patch:
>
> https://lore.kernel.org/linux-media/20240401233725.2401-1-laurent.pinchart@xxxxxxxxxxxxxxxx/
Referring to the discussion that has already taken place, we'd rather offer
a single API to control cropping and that is the selection API. But I agree
that there is a theoretical possibility someone might have set this to zero
and thus compilation could fail.
I'm sure this could be handled on the application still as there was never
anything to configure here. Breaking binary compatibility would be a real
issue but that's not what we have here.
--
Kind regards,
Sakari Ailus
