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, 134 insertions, 0 deletions

diff --git a/Documentation/userspace-api/media/v4l/vidioc-g-jpegcomp.rst b/Documentation/userspace-api/media/v4l/vidioc-g-jpegcomp.rst
new file mode 100644
index 000000000000..3b9981dcb8e0
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+++ b/Documentation/userspace-api/media/v4l/vidioc-g-jpegcomp.rst
@@ -0,0 +1,134 @@
+.. 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_G_JPEGCOMP:
+
+******************************************
+ioctl VIDIOC_G_JPEGCOMP, VIDIOC_S_JPEGCOMP
+******************************************
+
+Name
+====
+
+VIDIOC_G_JPEGCOMP - VIDIOC_S_JPEGCOMP
+
+
+Synopsis
+========
+
+.. c:function:: int ioctl( int fd, VIDIOC_G_JPEGCOMP, v4l2_jpegcompression *argp )
+    :name: VIDIOC_G_JPEGCOMP
+
+.. c:function:: int ioctl( int fd, VIDIOC_S_JPEGCOMP, const v4l2_jpegcompression *argp )
+    :name: VIDIOC_S_JPEGCOMP
+
+
+Arguments
+=========
+
+``fd``
+    File descriptor returned by :ref:`open() <func-open>`.
+
+``argp``
+    Pointer to struct :c:type:`v4l2_jpegcompression`.
+
+
+Description
+===========
+
+These ioctls are **deprecated**. New drivers and applications should use
+:ref:`JPEG class controls <jpeg-controls>` for image quality and JPEG
+markers control.
+
+[to do]
+
+Ronald Bultje elaborates:
+
+APP is some application-specific information. The application can set it
+itself, and it'll be stored in the JPEG-encoded fields (eg; interlacing
+information for in an AVI or so). COM is the same, but it's comments,
+like 'encoded by me' or so.
+
+jpeg_markers describes whether the huffman tables, quantization tables
+and the restart interval information (all JPEG-specific stuff) should be
+stored in the JPEG-encoded fields. These define how the JPEG field is
+encoded. If you omit them, applications assume you've used standard
+encoding. You usually do want to add them.
+
+
+.. tabularcolumns:: |p{1.2cm}|p{3.0cm}|p{13.3cm}|
+
+.. c:type:: v4l2_jpegcompression
+
+.. flat-table:: struct v4l2_jpegcompression
+    :header-rows:  0
+    :stub-columns: 0
+    :widths:       1 1 2
+
+    * - int
+      - ``quality``
+      - Deprecated. If
+	:ref:`V4L2_CID_JPEG_COMPRESSION_QUALITY <jpeg-quality-control>`
+	control is exposed by a driver applications should use it instead
+	and ignore this field.
+    * - int
+      - ``APPn``
+      -
+    * - int
+      - ``APP_len``
+      -
+    * - char
+      - ``APP_data``\ [60]
+      -
+    * - int
+      - ``COM_len``
+      -
+    * - char
+      - ``COM_data``\ [60]
+      -
+    * - __u32
+      - ``jpeg_markers``
+      - See :ref:`jpeg-markers`. Deprecated. If
+	:ref:`V4L2_CID_JPEG_ACTIVE_MARKER <jpeg-active-marker-control>`
+	control is exposed by a driver applications should use it instead
+	and ignore this field.
+
+
+.. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.7cm}|
+
+.. _jpeg-markers:
+
+.. flat-table:: JPEG Markers Flags
+    :header-rows:  0
+    :stub-columns: 0
+    :widths:       3 1 4
+
+    * - ``V4L2_JPEG_MARKER_DHT``
+      - (1<<3)
+      - Define Huffman Tables
+    * - ``V4L2_JPEG_MARKER_DQT``
+      - (1<<4)
+      - Define Quantization Tables
+    * - ``V4L2_JPEG_MARKER_DRI``
+      - (1<<5)
+      - Define Restart Interval
+    * - ``V4L2_JPEG_MARKER_COM``
+      - (1<<6)
+      - Comment segment
+    * - ``V4L2_JPEG_MARKER_APP``
+      - (1<<7)
+      - App segment, driver will always use APP0
+
+
+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.