Hi Laurent,
On Thu, Mar 21, 2024 at 07:03:08PM +0200, Laurent Pinchart wrote:
> Hello,
>
> On Wed, Mar 13, 2024 at 07:39:17AM +0000, Sakari Ailus wrote:
> > On Wed, Mar 13, 2024 at 09:34:13AM +0200, Tomi Valkeinen wrote:
> > > On 13/03/2024 09:25, Sakari Ailus wrote:
> > > > Add a flag to denote immutable routes, V4L2_SUBDEV_ROUTE_FL_IMMUTABLE.
> > > > Such routes cannot be changed and they're always active.
> > > >
> > > > Signed-off-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
> > > > ---
> > > > Documentation/userspace-api/media/v4l/dev-subdev.rst | 3 ++-
> > > > .../userspace-api/media/v4l/vidioc-subdev-g-routing.rst | 5 +++++
> > > > include/uapi/linux/v4l2-subdev.h | 5 +++++
> > > > 3 files changed, 12 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/Documentation/userspace-api/media/v4l/dev-subdev.rst b/Documentation/userspace-api/media/v4l/dev-subdev.rst
> > > > index 08495cc6f4a6..2f2423f676cf 100644
> > > > --- a/Documentation/userspace-api/media/v4l/dev-subdev.rst
> > > > +++ b/Documentation/userspace-api/media/v4l/dev-subdev.rst
> > > > @@ -572,7 +572,8 @@ internal pad always has a single stream only (0).
> > > > Routes from an internal source pad to an external source pad are typically not
> > > > modifiable but they can be activated and deactivated using the
> > > > :ref:`V4L2_SUBDEV_ROUTE_FL_ACTIVE <v4l2-subdev-routing-flags>` flag, depending
> > > > -on driver capabilities.
> > > > +on driver capabilities. This capatibility is indicated by the
> > > > +:ref:`V4L2_SUBDEV_ROUTE_FL_IMMUTABLE <v4l2-subdev-routing-flags>` flag.
>
> That's not very clear, it sounds like V4L2_SUBDEV_ROUTE_FL_IMMUTABLE
> indicates that the route can be enabled/disabled. I'd rewrite this.
I'll use instead:
The :ref:`V4L2_SUBDEV_ROUTE_FL_IMMUTABLE <v4l2-subdev-routing-flags>` flag
indicates that the ``V4L2_SUBDEV_ROUTE_FLAG_ACTIVE`` of the route may not
be unset.
>
> > > > Interaction between routes, streams, formats and selections
> > > > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > > > diff --git a/Documentation/userspace-api/media/v4l/vidioc-subdev-g-routing.rst b/Documentation/userspace-api/media/v4l/vidioc-subdev-g-routing.rst
> > > > index 08b8d17cef3f..cd7735f9104e 100644
> > > > --- a/Documentation/userspace-api/media/v4l/vidioc-subdev-g-routing.rst
> > > > +++ b/Documentation/userspace-api/media/v4l/vidioc-subdev-g-routing.rst
> > > > @@ -139,6 +139,11 @@ Also ``VIDIOC_SUBDEV_S_ROUTING`` may return more route than the user provided in
> > > > * - V4L2_SUBDEV_ROUTE_FL_ACTIVE
> > > > - 0x0001
> > > > - The route is enabled. Set by applications.
> > > > + * - V4L2_SUBDEV_ROUTE_FL_IMMUTABLE
> > > > + - 0x0002
> > > > + - The route is immutable. Set by the driver. The
> > > > + ``V4L2_SUBDEV_ROUTE_FL_ACTIVE`` flag of an immutable route may not be
> > > > + changed.
>
> May not be changed and will always be set ?
How about "may not be unset"?
>
> > > > Return Value
> > > > ============
> > > > diff --git a/include/uapi/linux/v4l2-subdev.h b/include/uapi/linux/v4l2-subdev.h
> > > > index ca543982460c..7e501cb45e4e 100644
> > > > --- a/include/uapi/linux/v4l2-subdev.h
> > > > +++ b/include/uapi/linux/v4l2-subdev.h
> > > > @@ -200,6 +200,11 @@ struct v4l2_subdev_capability {
> > > > * on a video node.
> > > > */
> > > > #define V4L2_SUBDEV_ROUTE_FL_ACTIVE (1U << 0)
> > > > +/*
> > > > + * Is the route immutable. The ACTIVE flag of an immutable route may not be
> > > > + * changed.
> > > > + */
> > > > +#define V4L2_SUBDEV_ROUTE_FL_IMMUTABLE (1U << 1)
> > > > /**
> > > > * struct v4l2_subdev_route - A route inside a subdev
> > >
> > > Is the route fully immutable? The sink/source stream ID cannot be changed
> > > (or any new fields we might come up with in the future)?
> >
> > I think the new fields should be considered separately when they're added.
> > This also applies to the stream IDs, I'll add this to the documentation.
> >
> > The naming of the flag is aligned with MC link flag with a similar purpose.
> >
> > > Hmm, or would a route with different stream IDs be a, well, different
> > > route...
> > >
> > > The docs here only talk about the ACTIVE flag. Would
> > > V4L2_SUBDEV_ROUTE_FL_ALWAYS_ACTIVE be a better name, to be more explicit on
> > > the meaning?
> >
> > I prefer immutable. I wonder what Laurent and Hans think.
>
> I'm fine with either. IMMUTABLE is shorter, if that makes a difference.
>
--
Kind regards,
Sakari Ailus
