media: docs: move uAPI book to userspace-api/media

Since 2017, there is an space reserved for userspace API,
created by changeset 1d596dee3862 ("docs: Create a user-space API guide").

As the media subsystem was one of the first subsystems to use
Sphinx, until this patch, we were keeping things on a separate
place.

Let's just use the new location, as having all uAPI altogether
will likely make things easier for developers.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

1 files changed, 167 insertions, 0 deletions

diff --git a/Documentation/userspace-api/media/v4l/vidioc-dbg-g-chip-info.rst b/Documentation/userspace-api/media/v4l/vidioc-dbg-g-chip-info.rst
new file mode 100644
index 000000000000..16078a2d3e3d
--- /dev/null
+++ b/Documentation/userspace-api/media/v4l/vidioc-dbg-g-chip-info.rst
@@ -0,0 +1,167 @@
+.. 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/userspace-api/media/fdl-appendix.rst.
+..
+.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections
+
+.. _VIDIOC_DBG_G_CHIP_INFO:
+
+****************************
+ioctl VIDIOC_DBG_G_CHIP_INFO
+****************************
+
+Name
+====
+
+VIDIOC_DBG_G_CHIP_INFO - Identify the chips on a TV card
+
+
+Synopsis
+========
+
+.. c:function:: int ioctl( int fd, VIDIOC_DBG_G_CHIP_INFO, struct v4l2_dbg_chip_info *argp )
+    :name: VIDIOC_DBG_G_CHIP_INFO
+
+
+Arguments
+=========
+
+``fd``
+    File descriptor returned by :ref:`open() <func-open>`.
+
+``argp``
+    Pointer to struct :c:type:`v4l2_dbg_chip_info`.
+
+
+Description
+===========
+
+.. note::
+
+    This is an :ref:`experimental` interface and may
+    change in the future.
+
+For driver debugging purposes this ioctl allows test applications to
+query the driver about the chips present on the TV card. Regular
+applications must not use it. When you found a chip specific bug, please
+contact the linux-media mailing list
+(`https://linuxtv.org/lists.php <https://linuxtv.org/lists.php>`__)
+so it can be fixed.
+
+Additionally the Linux kernel must be compiled with the
+``CONFIG_VIDEO_ADV_DEBUG`` option to enable this ioctl.
+
+To query the driver applications must initialize the ``match.type`` and
+``match.addr`` or ``match.name`` fields of a struct
+:c:type:`v4l2_dbg_chip_info` and call
+:ref:`VIDIOC_DBG_G_CHIP_INFO` with a pointer to this structure. On success
+the driver stores information about the selected chip in the ``name``
+and ``flags`` fields.
+
+When ``match.type`` is ``V4L2_CHIP_MATCH_BRIDGE``, ``match.addr``
+selects the nth bridge 'chip' on the TV card. You can enumerate all
+chips by starting at zero and incrementing ``match.addr`` by one until
+:ref:`VIDIOC_DBG_G_CHIP_INFO` fails with an ``EINVAL`` error code. The number
+zero always selects the bridge chip itself, e. g. the chip connected to
+the PCI or USB bus. Non-zero numbers identify specific parts of the
+bridge chip such as an AC97 register block.
+
+When ``match.type`` is ``V4L2_CHIP_MATCH_SUBDEV``, ``match.addr``
+selects the nth sub-device. This allows you to enumerate over all
+sub-devices.
+
+On success, the ``name`` field will contain a chip name and the
+``flags`` field will contain ``V4L2_CHIP_FL_READABLE`` if the driver
+supports reading registers from the device or ``V4L2_CHIP_FL_WRITABLE``
+if the driver supports writing registers to the device.
+
+We recommended the v4l2-dbg utility over calling this ioctl directly. It
+is available from the LinuxTV v4l-dvb repository; see
+`https://linuxtv.org/repo/ <https://linuxtv.org/repo/>`__ for access
+instructions.
+
+
+.. tabularcolumns:: |p{3.5cm}|p{3.5cm}|p{3.5cm}|p{7.0cm}|
+
+.. _name-v4l2-dbg-match:
+
+.. flat-table:: struct v4l2_dbg_match
+    :header-rows:  0
+    :stub-columns: 0
+    :widths:       1 1 2
+
+    * - __u32
+      - ``type``
+      - See :ref:`name-chip-match-types` for a list of possible types.
+    * - union {
+      - (anonymous)
+    * - __u32
+      - ``addr``
+      - Match a chip by this number, interpreted according to the ``type``
+	field.
+    * - char
+      - ``name[32]``
+      - Match a chip by this name, interpreted according to the ``type``
+	field. Currently unused.
+    * - }
+      -
+
+
+
+.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
+
+.. c:type:: v4l2_dbg_chip_info
+
+.. flat-table:: struct v4l2_dbg_chip_info
+    :header-rows:  0
+    :stub-columns: 0
+    :widths:       1 1 2
+
+    * - struct v4l2_dbg_match
+      - ``match``
+      - How to match the chip, see :ref:`name-v4l2-dbg-match`.
+    * - char
+      - ``name[32]``
+      - The name of the chip.
+    * - __u32
+      - ``flags``
+      - Set by the driver. If ``V4L2_CHIP_FL_READABLE`` is set, then the
+	driver supports reading registers from the device. If
+	``V4L2_CHIP_FL_WRITABLE`` is set, then it supports writing
+	registers.
+    * - __u32
+      - ``reserved[8]``
+      - Reserved fields, both application and driver must set these to 0.
+
+
+
+.. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.7cm}|
+
+.. _name-chip-match-types:
+
+.. flat-table:: Chip Match Types
+    :header-rows:  0
+    :stub-columns: 0
+    :widths:       3 1 4
+
+    * - ``V4L2_CHIP_MATCH_BRIDGE``
+      - 0
+      - Match the nth chip on the card, zero for the bridge chip. Does not
+	match sub-devices.
+    * - ``V4L2_CHIP_MATCH_SUBDEV``
+      - 4
+      - Match the nth sub-device.
+
+
+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.
+
+EINVAL
+    The ``match_type`` is invalid or no device could be matched.