Hi Sakari, Thank you for the patch. On Wed, Mar 13, 2024 at 09:24:48AM +0200, Sakari Ailus wrote: > Document S_ROUTING behaviour for different devices. > > Generally in devices that produce streams the streams are static and some > can be enabled and disabled, whereas in devices that just transport them > or write them to memory, more configurability is allowed. Document this. > > Signed-off-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx> > --- > .../userspace-api/media/v4l/dev-subdev.rst | 24 +++++++++++++++++++ > 1 file changed, 24 insertions(+) > > diff --git a/Documentation/userspace-api/media/v4l/dev-subdev.rst b/Documentation/userspace-api/media/v4l/dev-subdev.rst > index 1808f40f63e3..08495cc6f4a6 100644 > --- a/Documentation/userspace-api/media/v4l/dev-subdev.rst > +++ b/Documentation/userspace-api/media/v4l/dev-subdev.rst > @@ -593,6 +593,30 @@ Any configurations of a stream within a pad, such as format or selections, > are independent of similar configurations on other streams. This is > subject to change in the future. > > +Device types and routing setup > +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > + > +Different kinds of sub-devices have differing behaviour for route activation, > +depending on the hardware. In all cases, however, only routes that have the > +``V4L2_SUBDEV_STREAM_FL_ACTIVE`` flag set are active. > + > +Devices generating the streams may allow enabling and disabling some of the > +routes or the configuration is fixed. If the routes can be disabled, not > +declaring the routes (or declaring them without > +``VIDIOC_SUBDEV_STREAM_FL_ACTIVE`` flag set) in ``VIDIOC_SUBDEV_S_ROUTING`` will > +disable the routes while the sub-device driver retains the streams and their No idea what you mean by "retains the streams and their configuration". > +configuration. The ``VIDIOC_SUBDEV_S_ROUTING`` will still return such routes > +back to the user in the routes array, with the ``V4L2_SUBDEV_STREAM_FL_ACTIVE`` > +flag unset. I find this quite confusing. There's no explanation as to why the API behaves this way. I think you should rewrite this documentation, trying to evaluate it from the point of view of someone who doesn't know about the routing API. > + > +Devices transporting the streams almost always have more configurability with > +respect to routing. Typically any route between the sub-device's sink and source > +pads is possible, and multiple routes (usually up to certain limited number) may > +be active simultaneously. For such devices, no routes are created by the driver > +and user-created routes are fully replaced when ``VIDIOC_SUBDEV_S_ROUTING`` is > +called on the sub-device. Such newly created routes have the device's default > +configuration for format and selection rectangles. > + > Configuring streams > ^^^^^^^^^^^^^^^^^^^ > -- Regards, Laurent Pinchart
