Hi Sakari, thanks for the review On Thu, Mar 07, 2019 at 05:19:29PM +0200, Sakari Ailus wrote: > Hi Jacopo, > > Thanks for writing the documentation for this! > > The text is nice and informative; I have a few suggestions below. > > On Tue, Mar 05, 2019 at 07:51:38PM +0100, Jacopo Mondi wrote: > > Add documentation for VIDIOC_SUBDEV_G/S_ROUTING ioctl and add > > description of multiplexed media pads and internal routing to the > > V4L2-subdev documentation section. > > > > Signed-off-by: Jacopo Mondi > > --- > > Documentation/media/uapi/v4l/dev-subdev.rst | 90 +++++++++++ > > Documentation/media/uapi/v4l/user-func.rst | 1 + > > .../uapi/v4l/vidioc-subdev-g-routing.rst | 142 ++++++++++++++++++ > > 3 files changed, 233 insertions(+) > > create mode 100644 Documentation/media/uapi/v4l/vidioc-subdev-g-routing.rst > > > > diff --git a/Documentation/media/uapi/v4l/dev-subdev.rst b/Documentation/media/uapi/v4l/dev-subdev.rst > > index 2c2768c7343b..b9fbb5d2caec 100644 > > --- a/Documentation/media/uapi/v4l/dev-subdev.rst > > +++ b/Documentation/media/uapi/v4l/dev-subdev.rst > > @@ -36,6 +36,8 @@ will feature a character device node on which ioctls can be called to > > > > - negotiate image formats on individual pads > > > > +- inspect and modify internal data routing between pads of the same entity > > + > > Sub-device character device nodes, conventionally named > > ``/dev/v4l-subdev*``, use major number 81. > > > > @@ -461,3 +463,91 @@ source pads. > > :maxdepth: 1 > > > > subdev-formats > > + > > + > > +Multiplexed media pads and internal routing > > +------------------------------------------- > > + > > +Subdevice drivers might expose the internal connections between media pads of an > > s/might/may/ > > > +entity by providing a routing table that applications can inspect and manipulate > > s/providing/exposing/ > Ack on both the above suggestions > > +to change the internal routing between sink and source pads' data connection > > +endpoints. A routing table is described by a struct > > +:c:type:`v4l2_subdev_routing`, which contains ``num_routes`` route entries, each > > +one represented by a struct :c:type:`v4l2_subdev_route`. > > + > > +Data routes do not just connect one pad to another in an entity, but they refer > > +instead to the ``streams`` a media pad provides. Streams are data connection > > +endpoints in a media pad. Multiplexed media pads expose multiple ``streams`` > > +which represent, when the underlying hardware technology allows that, logical > > +data streams transported over a single physical media bus. > > How about s/streams/flows/ for this instance? > Agreed, there are too many "streams" already in that paragraph > > + > > +One of the most notable examples of logical stream multiplexing techniques is > > s/One of the most notable examples/A noteworthy example/ > > > +represented by the data interleaving mechanism implemented by mean of Virtual > > +Channels identifiers as defined by the MIPI CSI-2 media bus specifications. A > > s/identifiers // > Ack on both the above suggestions > > +subdevice that implements support for Virtual Channel data interleaving might > > +expose up to 4 data ``streams``, one for each available Virtual Channel, on the > > +source media pad that represents a CSI-2 connection endpoint. > > + > > +Routes are defined as potential data connections between a ``(sink_pad, > > +sink_stream)`` pair and a ``(source_pad, source_stream)`` one, where > > +``sink_pad`` and ``source_pad`` are the indexes of two media pads part of the > > +same media entity, and ``sink_stream`` and ``source_stream`` are the identifiers > > +of the data streams to be connected in the media pads. Media pads that do not > > +support data multiplexing expose a single stream, usually with identifier 0. > > + > > +Routes are reported to applications in a routing table which can be > > +inspected and manipulated using the :ref:`routing ` > > +ioctls. > > + > > +Routes can be activated and deactivated by setting or clearing the > > +V4L2_SUBDEV_ROUTE_FL_ACTIVE flag in the ``flags`` field of struct > > +:c:type:`v4l2_subdev_route`. > > + > > +Subdev driver might create routes that cannot be modified by applications. Such > > s/S/A s/ Or "Subdevice drivers" ? > > > +routes are identified by the presence of the V4L2_SUBDEV_ROUTE_FL_IMMUTABLE > > +flag in the ``flags`` field of struct :c:type:`v4l2_subdev_route`. > > + > > +As an example, the routing table of a source pad which supports two logical > > +video streams and can be connected to two sink pads is here below described. > > + > > +.. flat-table:: > > + :widths: 1 2 1 > > + > > + * - Pad Index > > + - Function > > + - Number of streams > > + * - 0 > > + - SINK > > + - 1 > > + * - 1 > > + - SINK > > + - 1 > > + * - 2 > > + - SOURCE > > + - 2 > > + > > +In such an example, the source media pad will report a routing table with 4 > > +entries, one entry for each possible ``(sink_pad, sink_stream) - (source_pad, > > +source_stream)`` combination. > > + > > +.. flat-table:: routing table > > + :widths: 2 1 2 > > + > > + * - Sink Pad/Sink Stream > > + - -> > > + - Source Pad/Source Stream > > + * - 0/0 > > + - -> > > + - 2/0 > > + * - 0/0 > > + - -> > > + - 2/1 > > + * - 1/0 > > + - -> > > + - 2/0 > > + * - 1/0 > > + - -> > > + - 2/1 > > + > > +Subdev drivers are free to decide how many routes an application can enable on > > +a media pad at the same time, and refuse to enable or disable specific routes. > > diff --git a/Documentation/media/uapi/v4l/user-func.rst b/Documentation/media/uapi/v4l/user-func.rst > > index ca0ef21d77fe..0166446f4ab4 100644 > > --- a/Documentation/media/uapi/v4l/user-func.rst > > +++ b/Documentation/media/uapi/v4l/user-func.rst > > @@ -77,6 +77,7 @@ Function Reference > > vidioc-subdev-g-crop > > vidioc-subdev-g-fmt > > vidioc-subdev-g-frame-interval > > + vidioc-subdev-g-routing > > vidioc-subdev-g-selection > > vidioc-subscribe-event > > func-mmap > > diff --git a/Documentation/media/uapi/v4l/vidioc-subdev-g-routing.rst b/Documentation/media/uapi/v4l/vidioc-subdev-g-routing.rst > > new file mode 100644 > > index 000000000000..8b592722c477 > > --- /dev/null > > +++ b/Documentation/media/uapi/v4l/vidioc-subdev-g-routing.rst > > @@ -0,0 +1,142 @@ > > +.. Permission is granted to copy, distribute and/or modify this > > +.. document under the terms of the GNU Free Documentation License, > > +.. Version 1.1 or any later version published by the Free Software > > +.. Foundation, with no Invariant Sections, no Front-Cover Texts > > +.. and no Back-Cover Texts. A copy of the license is included at > > +.. Documentation/media/uapi/fdl-appendix.rst. > > +.. > > +.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections > > + > > +.. _VIDIOC_SUBDEV_G_ROUTING: > > + > > +****************************************************** > > +ioctl VIDIOC_SUBDEV_G_ROUTING, VIDIOC_SUBDEV_S_ROUTING > > +****************************************************** > > + > > +Name > > +==== > > + > > +VIDIOC_SUBDEV_G_ROUTING - VIDIOC_SUBDEV_S_ROUTING - Get or set routing between streams of media pads in a media entity. > > + > > + > > +Synopsis > > +======== > > + > > +.. c:function:: int ioctl( int fd, VIDIOC_SUBDEV_G_ROUTING, struct v4l2_subdev_routing *argp ) > > + :name: VIDIOC_SUBDEV_G_ROUTING > > + > > +.. c:function:: int ioctl( int fd, VIDIOC_SUBDEV_S_ROUTING, struct v4l2_subdev_routing *argp ) > > + :name: VIDIOC_SUBDEV_S_ROUTING > > + > > + > > +Arguments > > +========= > > + > > +``fd`` > > + File descriptor returned by :ref:`open() `. > > + > > +``argp`` > > + Pointer to struct :c:type:`v4l2_subdev_routing`. > > + > > + > > +Description > > +=========== > > + > > +These ioctls are used to get and set the routing informations associated to > > +media pads in a media entity. Routing informations are used to enable or disable > > The routing is a property of an entity. How about > > s/the routing informations associated to media pads in/routing/ > > s/R[^\.]+(?=\.)/The routing configuration determines the flows of data > inside an entity/ Thanks, you made me discover regexr.com here > > > +data connections between stream endpoints of multiplexed media pads. > > + > > +Drivers report their routing tables using VIDIOC_SUBDEV_G_ROUTING and > > +application use the information there reported to enable or disable data > > +connections between streams in a pad, by setting or clearing the > > How about: > > s/applications\K.*a pad/may enable or disable routes with the > VIDIOC_SUBDEV_S_ROUTING IOCTL, > Yes, reads better > > +V4L2_SUBDEV_ROUTE_FL_ACTIVE flag of ``flags`` field of a struct > > +:c:type:`v4l2_subdev_route`. > > + > > +When inspecting routes through VIDIOC_SUBDEV_G_ROUTING and the application > > +provided ``num_routes`` is not big enough to contain all the available routes > > +the subdevice exposes, drivers return the ENOSPC error code and adjust the > > +``num_routes`` value. Application should then reserve enough memory for all the > > s/the\K$/value of the/ > s/value\K\./field/ > Will update > > +route entries and call VIDIOC_SUBDEV_G_ROUTING again. > > + > > +.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}| > > + > > +.. c:type:: v4l2_subdev_routing > > + > > +.. flat-table:: struct v4l2_subdev_routing > > + :header-rows: 0 > > + :stub-columns: 0 > > + :widths: 1 1 2 > > + > > + * - struct :c:type:`v4l2_subdev_route` > > + - ``routes[]`` > > + - Array of struct :c:type:`v4l2_subdev_route` entries > > + * - __u32 > > + - ``num_routes`` > > + - Number of entries of the routes array > > + * - __u32 > > + - ``reserved``\ [5] > > + - Reserved for future extensions. Applications and drivers must set > > + the array to zero. > > + > > +.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}| > > + > > +.. c:type:: v4l2_subdev_route > > + > > +.. flat-table:: struct v4l2_subdev_route > > + :header-rows: 0 > > + :stub-columns: 0 > > + :widths: 1 1 2 > > + > > + * - __u32 > > + - ``sink_pad`` > > + - Sink pad number > > + * - __u32 > > + - ``sink_stream`` > > + - Sink pad stream number > > + * - __u32 > > + - ``source_stream`` > > + - Source pad stream number > > + * - __u32 > > + - ``sink_stream`` > > + - Sink pad stream number > > + * - __u32 > > + - ``flags`` > > + - Route enable/disable flags > > + :ref:`v4l2_subdev_routing_flags `. > > + * - __u32 > > + - ``reserved``\ [5] > > + - Reserved for future extensions. Applications and drivers must set > > + the array to zero. > > + > > +.. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.7cm}| > > + > > +.. _v4l2-subdev-routing-flags: > > + > > +.. flat-table:: enum v4l2_subdev_routing_flags > > + :header-rows: 0 > > + :stub-columns: 0 > > + :widths: 3 1 4 > > + > > + * - V4L2_SUBDEV_ROUTE_FL_ACTIVE > > + - 0 > > + - The route is enabled. Set by applications. > > + * - V4L2_SUBDEV_ROUTE_FL_IMMUTABLE > > + - 1 > > + - The route is immutable. Set by the driver. > > + > > +Return Value > > +============ > > + > > +On success 0 is returned, on error -1 and the ``errno`` variable is set > > +appropriately. The generic error codes are described at the > > +:ref:`Generic Error Codes ` chapter. > > + > > +ENOSPC > > + The number of provided route entries is less than the available ones. > > + > > +EINVAL > > + The sink or source pad identifiers reference a non-existing pad, or refernce > > + pads of different types (ie. the sink_pad identifiers refers to a source pad) > > + The sink or source stream identifiers reference a non-existing stream > > s/The/or the/ > > > + in the sink or source pad. > > s/i/o/ Thanks, I will update all of these in v4. > > > + > > -- > Kind regards, > > Sakari Ailus > sakari.ailus@linux.intel.com