Re: [PATCH v4 20/29] media: uapi: Bump the STREAMS bit a little

Laurent Pinchart
2026-04-21T11:19:01Z

On Tue, Apr 21, 2026 at 01:27:36PM +0300, Sakari Ailus wrote:
> On Thu, Apr 16, 2026 at 05:31:12PM +0300, Laurent Pinchart wrote:
> > On Fri, Apr 10, 2026 at 11:31:06AM +0200, Jacopo Mondi wrote:
> > > On Wed, Apr 08, 2026 at 06:39:29PM +0300, Sakari Ailus wrote:
> > > > Bump the V4L2_SUBDEV_CAP_STREAMS by one bit up, order to avoid confusing
> > > > libcamera with streams that has moved forward from the original libcamera
> > > > implementation. The bit can presumably be taken into use but only after
> > > > the other free bits.
> > > >
> > > > Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
> > >
> > > Thanks!
> > > Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
> > >
> > > > ---
> > > > include/uapi/linux/v4l2-subdev.h | 5 ++++-
> > > > 1 file changed, 4 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/include/uapi/linux/v4l2-subdev.h b/include/uapi/linux/v4l2-subdev.h
> > > > index 2347e266cf75..6160c3e21436 100644
> > > > --- a/include/uapi/linux/v4l2-subdev.h
> > > > +++ b/include/uapi/linux/v4l2-subdev.h
> > > > @@ -196,8 +196,11 @@ struct v4l2_subdev_capability {
> > > > /* The v4l2 sub-device video device node is registered in read-only mode. */
> > > > #define V4L2_SUBDEV_CAP_RO_SUBDEV 0x00000001
> > > >
> > > > +/* Reserved, old STREAMS bit libcamera used before API stabilisation. */
> > > > +/* #define V4L2_SUBDEV_CAP_STREAMS_PRELIMINARY 0x00000002 */
> > >
> > > This should make sure libcamera versions which support the new flag
> > > won't match agains older kernel which use the old value!
> >
> > Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
> >
> > Could we delay merging this patch until we work on implementing the new
> > behaviour in libcamera ?
>
> I guess we're not in hurry to merge this although I don't see the direct
> connection to libcamera. Are you worried someone could start using this bit
> instead before wget things entirely stabilised? :-)

That's exactly my concern, yes.

> > > > +
> > > > /* The v4l2 sub-device supports routing and multiplexed streams. */
> > > > -#define V4L2_SUBDEV_CAP_STREAMS 0x00000002
> > > > +#define V4L2_SUBDEV_CAP_STREAMS 0x00000004
> > > >
> > > > /*
> > > > * Is the route active? An active route will start when streaming is enabled

--
Regards,

Laurent Pinchart