Hi Hans, Thank you for the review. On Tue, Aug 08, 2023 at 10:55:24AM +0200, Hans Verkuil wrote: > On 08/08/2023 09:55, Sakari Ailus wrote: > > Document how internal pads are used on source routes. > > > > Signed-off-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx> > > --- > > .../userspace-api/media/v4l/dev-subdev.rst | 179 ++++++++++++++++++ > > 1 file changed, 179 insertions(+) > > > > diff --git a/Documentation/userspace-api/media/v4l/dev-subdev.rst b/Documentation/userspace-api/media/v4l/dev-subdev.rst > > index b023918177b5..27b0fe2dc83a 100644 > > --- a/Documentation/userspace-api/media/v4l/dev-subdev.rst > > +++ b/Documentation/userspace-api/media/v4l/dev-subdev.rst > > @@ -551,6 +551,27 @@ A stream at a specific point in the media pipeline is identified by the > > sub-device and a (pad, stream) pair. For sub-devices that do not support > > multiplexed streams the 'stream' field is always 0. > > > > +.. _v4l2-subdev-source-routes: > > + > > +Internal pads and source routes > > +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > > + > > +Cases where a single sub-device source pad is traversed by multiple streams one > > +or more of which originate from within the sub-device itself are special as > > +there is no external sink pad for such routes. In those cases, the sources of > > +the internally generated streams are represented by internal sink pads, which > > +are sink pads that have the :ref:`MEDIA_PAD_FL_INTERNAL <MEDIA-PAD-FL-INTERNAL>` > > +pad flag set. > > + > > +Internal pads have all the properties of an external pad, including formats and > > +selections. The format in this case is the source format of the stream. An > > +internal pad always has a single stream only (0). > > + > > +/Source routes/ are routes from an internal sink pad to a(n external) source > > '/Source routes/' appears just like that in the generated documentation, that's > probably not what you intended. This was intended to be *Source routes*. I'll address it in v4. > > > +pad. Generally source routes are 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. > > + > > Interaction between routes, streams, formats and selections > > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > > > > @@ -666,3 +687,161 @@ A common way to accomplish this is to start from the sensors and propagate the > > configurations along the stream towards the receiver, > > using :ref:`VIDIOC_SUBDEV_S_FMT <VIDIOC_SUBDEV_G_FMT>` ioctls to configure each > > stream endpoint in each sub-device. > > + > > +Internal pads setup example > > +^^^^^^^^^^^^^^^^^^^^^^^^^^^ > > + > > +A simple example of a multiplexed stream setup might be as follows: > > + > > +- A CCS camera sensor source sub-device, with one sink pad (0), one source pad > > Explain what 'CCS' means: probably a link to MIPI CCS is sufficient, but for newbies > 'CCS' doesn't provide any information. > > > + (1), an internal sink pad (2) that represents the source of embedded > > So since the INTERNAL flag is associated with a sink pad, this is now called an > 'internal sink' instead of 'internal source' as it was before. I agree with that, > but note that the phrase 'internal source' is still used in several places, > including the cover letter. For the next version you post, please check for that > and change the terminology since mixing the two is very confusing :-) Are you referring to this patch? There don't seem to be any references to "intenal source pads" left. > > > + data. There are two routes, one from the sink pad to the source, and another > > + from the internal sink pad to the source pad. The embedded data stream needs > > + to be enabled by activating the related route. The configuration of the rest > > + of the CCS sub-devices is omitted from this example. > > + > > +- Multiplexer bridge (Bridge). The bridge has one sink pad, connected to the > > + sensor (pad 0), and one source pad (pad 1), which outputs two streams. > > + > > +- Receiver in the SoC (Receiver). The receiver has a single sink pad (pad 0), > > + connected to the bridge, and two source pads (pads 1-2), going to the DMA > > + engine. The receiver demultiplexes the incoming streams to the source pads. > > + > > +- DMA Engines in the SoC (DMA Engine), one for each stream. Each DMA engine is > > + connected to a single source pad in the receiver. > > + > > +The sensor, the bridge and the receiver are modeled as V4L2 sub-devices, > > +exposed to userspace via /dev/v4l-subdevX device nodes. The DMA engines are > > +modeled as V4L2 devices, exposed to userspace via /dev/videoX nodes. > > + > > +To configure this pipeline, the userspace must take the following steps: > > + > > +1) Set up media links between entities: connect the sensors to the bridge, > > + bridge to the receiver, and the receiver to the DMA engines. This step does > > + not differ from normal non-multiplexed media controller setup. > > + > > +2) Configure routing > > + > > +.. flat-table:: Camera sensor > > + :header-rows: 1 > > + > > + * - Sink Pad/Stream > > + - Source Pad/Stream > > + - Routing Flags > > + - Comments > > + * - 0/0 > > + - 1/0 > > + - V4L2_SUBDEV_ROUTE_FL_ACTIVE > > + - Pixel data stream from the sink pad > > Huh? It is a sensor subdev, so aren't both pixel data and metadata > coming from an internal sink? The CCS driver exposes three sub-devices, so in this case the sink pad isn't internal. Almost (?) all other sensor drivers have a single sub-device only, perhaps I'll change the example to align with one of those. > > I think you are actually describing the internal subdev of a CCS > sensor here, but that is not clear from the description at all. > > Since CCS sensors are relatively common (I think), it might be > good to give a fully fledged example. > > But suppose you have a non-CCS sensor that generates the pixel data > and metadata, then you would have two internal sink pads and one > source pad for two streams, right? > > And very simple sensors that currently just have a single source pad > could be describes as having an internal sink pad connected to the > source pad by a fixed route. But we don't do that, because it is > overkill. Correct? If so, then this might be useful information to add > to answer the question why some sensors have internal sinks and others > do not. > > > + * - 2/0 > > + - 1/1 > > + - **V4L2_SUBDEV_ROUTE_FL_ACTIVE** > > + - Metadata stream from the internal sink pad > > + > > +.. flat-table:: Bridge routing table > > + :header-rows: 1 > > + > > + * - Sink Pad/Stream > > + - Source Pad/Stream > > + - Routing Flags > > + - Comments > > + * - 0/0 > > + - 1/0 > > + - V4L2_SUBDEV_ROUTE_FL_ACTIVE > > + - Pixel data stream from camera sensor > > + * - 0/1 > > + - 1/1 > > + - V4L2_SUBDEV_ROUTE_FL_ACTIVE > > + - Metadata stream from camera sensor > > + > > +.. flat-table:: Receiver routing table > > + :header-rows: 1 > > + > > + * - Sink Pad/Stream > > + - Source Pad/Stream > > + - Routing Flags > > + - Comments > > + * - 0/0 > > + - 1/0 > > + - V4L2_SUBDEV_ROUTE_FL_ACTIVE > > + - Pixel data stream from camera sensor > > + * - 0/1 > > + - 2/0 > > + - V4L2_SUBDEV_ROUTE_FL_ACTIVE > > + - Metadata stream from camera sensor > > + > > +The options available in sensor's routing configuration are dictated by hardware > > +capabilities: typically camera sensors always produce image data stream while > > +the embedded data stream typically can be either enabled or disabled. > > + > > +3) Configure formats and selections > > + > > +This example assumes that the formats are propagated from sink pad to the source > > +pad as-is. The tables contain fields of both struct v4l2_subdev_format and > > +struct v4l2_mbus_framefmt. The full configuration of CCS camera sensor is out of > > +scope of this example. > > + > > +.. flat-table:: Formats set on the sub-devices. Bold values are set, others are > > + static or propagated. > > + :header-rows: 1 > > + :fill-cells: > > + > > + * - Sub-device > > + - Pad/Stream > > + - Width > > + - Height > > + - Code > > + * - :rspan:`3` Camera sensor sub-device (CCS source sub-device) > > + - 0/0 > > + - 640 > > + - 480 > > + - MEDIA_BUS_FMT_SGRBG10 > > + * - 1/0 > > + - 640 > > + - 480 > > + - **MEDIA_BUS_FMT_SGRBG10** > > + * - 2/0 > > + - 640 > > + - 2 > > + - MEDIA_BUS_FMT_CCS_EMBEDDED_10 > > + * - 1/1 > > + - 640 > > + - 2 > > + - MEDIA_BUS_FMT_META_10 > > + * - :rspan:`3` Bridge > > + - 0/0 > > + - **640** > > + - **480** > > + - **MEDIA_BUS_FMT_SGRBG10** > > + * - 1/0 > > + - 640 > > + - 480 > > + - MEDIA_BUS_FMT_SGRBG10 > > + * - 0/1 > > + - **640** > > + - **2** > > + - **MEDIA_BUS_FMT_META_10** > > + * - 1/1 > > + - 640 > > + - 2 > > + - MEDIA_BUS_FMT_META_10 > > + * - :rspan:`3` Receiver > > + - 0/0 > > + - **640** > > + - **480** > > + - **MEDIA_BUS_FMT_SGRBG10** > > + * - 1/0 > > + - 640 > > + - 480 > > + - MEDIA_BUS_FMT_SGRBG10 > > + * - 0/1 > > + - **640** > > + - **2** > > + - **MEDIA_BUS_FMT_META_10** > > + * - 2/0 > > + - 640 > > + - 2 > > + - MEDIA_BUS_FMT_META_10 > > + > > +The embedded data format does not need to be configured as the format is > > +dictated by the pixel data format in this case. -- Kind regards, Sakari Ailus
