| Message ID | 20240313072516.241106-11-sakari.ailus@linux.intel.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [v8,01/38] media: mc: Add INTERNAL pad flag | expand |
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@linux.intel.com> > --- > .../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 > ^^^^^^^^^^^^^^^^^^^ >
Hi Laurent, On Wed, Mar 20, 2024 at 02:33:16AM +0200, Laurent Pinchart wrote: > 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@linux.intel.com> > > --- > > .../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". I'll add that this means format and selection 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. I wonder if this would be easier for the user if such routes had a flag that would tell they're always there. It could be called e.g. STATIC. Then the user would be able to expect certain behaviour before disabling a link. The purpose is really to avoid removing streams that the user would not know how to re-create in order to make the device function again. > > > + > > +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 > > ^^^^^^^^^^^^^^^^^^^ > > >
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 +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. + +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 ^^^^^^^^^^^^^^^^^^^
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@linux.intel.com> --- .../userspace-api/media/v4l/dev-subdev.rst | 24 +++++++++++++++++++ 1 file changed, 24 insertions(+)