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From: Jacopo Mondi <jacopo+renesas@jmondi.org>
To: sakari.ailus@linux.intel.com, laurent.pinchart@ideasonboard.com,
	niklas.soderlund+renesas@ragnatech.se
Cc: Jacopo Mondi <jacopo+renesas@jmondi.org>,
	linux-media@vger.kernel.org, linux-renesas-soc@vger.kernel.org
Subject: [PATCH v3 19/31] media: Documentation: Add GS_ROUTING documentation
Date: Tue,  5 Mar 2019 19:51:38 +0100	[thread overview]
Message-ID: <20190305185150.20776-20-jacopo+renesas@jmondi.org> (raw)
In-Reply-To: <20190305185150.20776-1-jacopo+renesas@jmondi.org>

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 <jacopo+renesas@jmondi.org>
---
 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
+entity by providing a routing table that applications can inspect and manipulate
+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.
+
+One of the most notable examples of logical stream multiplexing techniques is
+represented by the data interleaving mechanism implemented by mean of Virtual
+Channels identifiers as defined by the MIPI CSI-2 media bus specifications. A
+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 <VIDIOC_SUBDEV_G_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
+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() <func-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
+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
+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
+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 <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 <gen-errors>` 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
+   in the sink or source pad.
+
-- 
2.20.1


  parent reply	other threads:[~2019-03-05 18:51 UTC|newest]

Thread overview: 59+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-05 18:51 [PATCH v3 00/31] v4l: add support for multiplexed streams Jacopo Mondi
2019-03-05 18:51 ` [PATCH v3 01/31] media: entity: Use pad as a starting point for graph walk Jacopo Mondi
2019-03-05 18:51 ` [PATCH v3 02/31] media: entity: Use pads instead of entities in the media graph walk stack Jacopo Mondi
2019-03-05 18:51 ` [PATCH v3 03/31] media: entity: Walk the graph based on pads Jacopo Mondi
2019-03-05 18:51 ` [PATCH v3 04/31] v4l: mc: Start walk from a specific pad in use count calculation Jacopo Mondi
2019-03-05 18:51 ` [PATCH v3 05/31] media: entity: Add iterator helper for entity pads Jacopo Mondi
2019-03-05 18:51 ` [PATCH v3 06/31] media: entity: Move the pipeline from entity to pads Jacopo Mondi
2019-03-05 18:51 ` [PATCH v3 07/31] media: entity: Use pad as the starting point for a pipeline Jacopo Mondi
2019-03-05 18:51 ` [PATCH v3 08/31] media: entity: Add has_route entity operation Jacopo Mondi
2019-03-05 18:51 ` [PATCH v3 09/31] media: entity: Add media_has_route() function Jacopo Mondi
2019-03-14 14:45   ` Luca Ceresoli
2019-03-15  9:22     ` Jacopo Mondi
2019-03-05 18:51 ` [PATCH v3 10/31] media: entity: Use routing information during graph traversal Jacopo Mondi
2019-03-05 18:51 ` [PATCH v3 11/31] media: entity: Skip link validation for pads to which there is no route to Jacopo Mondi
2019-03-05 18:51 ` [PATCH v3 12/31] media: entity: Add an iterator helper for connected pads Jacopo Mondi
2019-03-07 10:09   ` Sakari Ailus
2019-03-07 10:27     ` Ian Arkver
2019-03-07 12:38       ` Sakari Ailus
2019-03-07 20:18       ` Jacopo Mondi
2019-03-05 18:51 ` [PATCH v3 13/31] media: entity: Add only connected pads to the pipeline Jacopo Mondi
2019-03-05 18:51 ` [PATCH v3 14/31] media: entity: Add debug information in graph walk route check Jacopo Mondi
2019-03-05 18:51 ` [PATCH v3 15/31] v4l: Add bus type to frame descriptors Jacopo Mondi
2019-03-05 18:51 ` [PATCH v3 16/31] v4l: Add CSI-2 bus configuration " Jacopo Mondi
2019-03-05 18:51 ` [PATCH v3 17/31] v4l: Add stream to frame descriptor Jacopo Mondi
2019-03-05 18:51 ` [PATCH v3 18/31] v4l: subdev: Add [GS]_ROUTING subdev ioctls and operations Jacopo Mondi
2019-03-05 18:51 ` Jacopo Mondi [this message]
2019-03-07 15:19   ` [PATCH v3 19/31] media: Documentation: Add GS_ROUTING documentation Sakari Ailus
2019-03-08 13:31     ` Jacopo Mondi
2019-03-08 14:14       ` Sakari Ailus
2019-03-14 14:44     ` Luca Ceresoli
2019-03-14 14:43   ` Luca Ceresoli
2020-02-13 13:36   ` Hans Verkuil
2019-03-05 18:51 ` [PATCH v3 20/31] v4l: subdev: Take routing information into account in link validation Jacopo Mondi
2019-03-05 18:51 ` [PATCH v3 21/31] v4l: subdev: Improve link format validation debug messages Jacopo Mondi
2019-03-05 18:51 ` [PATCH v3 22/31] v4l: mc: Add an S_ROUTING helper function for power state changes Jacopo Mondi
2019-03-05 18:51 ` [PATCH v3 23/31] adv748x: csi2: add translation from pixelcode to CSI-2 datatype Jacopo Mondi
2019-03-05 18:51 ` [PATCH v3 24/31] adv748x: csi2: only allow formats on sink pads Jacopo Mondi
2019-03-05 18:51 ` [PATCH v3 25/31] adv748x: csi2: describe the multiplexed stream Jacopo Mondi
2019-03-05 18:51 ` [PATCH v3 26/31] adv748x: csi2: add internal routing configuration Jacopo Mondi
2019-03-14 14:45   ` Luca Ceresoli
2019-03-15  9:45     ` Jacopo Mondi
2019-03-15 10:06       ` Sakari Ailus
2019-03-16 10:23         ` Luca Ceresoli
2019-03-20 17:14           ` Jacopo Mondi
2019-03-22 16:52             ` Luca Ceresoli
2019-03-28 15:08               ` Jacopo Mondi
2019-03-28 15:17                 ` Luca Ceresoli
2019-03-05 18:51 ` [PATCH v3 27/31] adv748x: afe: add routing support Jacopo Mondi
2019-03-05 18:51 ` [PATCH v3 28/31] adv748x: afe: Implement has_route() Jacopo Mondi
2019-03-07 12:49   ` Sakari Ailus
2019-03-14 14:45   ` Luca Ceresoli
2019-03-05 18:51 ` [PATCH v3 29/31] rcar-csi2: use frame description information to configure CSI-2 bus Jacopo Mondi
2019-03-05 18:51 ` [PATCH v3 30/31] rcar-csi2: expose the subdevice internal routing Jacopo Mondi
2019-03-05 18:51 ` [PATCH v3 31/31] media: rcar-csi2: Implement has_route() Jacopo Mondi
2019-03-07 12:56   ` Sakari Ailus
2019-03-07 22:28     ` Jacopo Mondi
2019-03-07  9:47 ` [PATCH v3 00/31] v4l: add support for multiplexed streams Sakari Ailus
2019-03-08 13:19   ` Jacopo Mondi
2019-03-08 14:12     ` Sakari Ailus

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