[PATCH v5 7/7] media: docs: add documentation for the Extended API

Helen Koike
2020-08-04T19:32:45Z

Add documentation and update references in current documentation for the
Extended API.

Signed-off-by: Helen Koike <helen.koike@collabora.com>
---
Changes in v5:
- new patch

.../userspace-api/media/v4l/buffer.rst | 5 +
.../userspace-api/media/v4l/common.rst | 1 +
.../userspace-api/media/v4l/dev-capture.rst | 5 +
.../userspace-api/media/v4l/dev-output.rst | 5 +
.../userspace-api/media/v4l/ext-api.rst | 107 +++++++++
.../userspace-api/media/v4l/format.rst | 16 +-
.../userspace-api/media/v4l/user-func.rst | 5 +
.../media/v4l/vidioc-ext-create-bufs.rst | 95 ++++++++
.../media/v4l/vidioc-ext-prepare-buf.rst | 62 ++++++
.../media/v4l/vidioc-ext-qbuf.rst | 204 ++++++++++++++++++
.../media/v4l/vidioc-ext-querybuf.rst | 79 +++++++
.../media/v4l/vidioc-g-ext-pix-fmt.rst | 117 ++++++++++
12 files changed, 697 insertions(+), 4 deletions(-)
create mode 100644 Documentation/userspace-api/media/v4l/ext-api.rst
create mode 100644 Documentation/userspace-api/media/v4l/vidioc-ext-create-bufs.rst
create mode 100644 Documentation/userspace-api/media/v4l/vidioc-ext-prepare-buf.rst
create mode 100644 Documentation/userspace-api/media/v4l/vidioc-ext-qbuf.rst
create mode 100644 Documentation/userspace-api/media/v4l/vidioc-ext-querybuf.rst
create mode 100644 Documentation/userspace-api/media/v4l/vidioc-g-ext-pix-fmt.rst

diff --git a/Documentation/userspace-api/media/v4l/buffer.rst b/Documentation/userspace-api/media/v4l/buffer.rst
index 57e752aaf414a..c832bedd64e4c 100644
--- a/Documentation/userspace-api/media/v4l/buffer.rst
+++ b/Documentation/userspace-api/media/v4l/buffer.rst
@@ -27,6 +27,11 @@ such as pointers and sizes for each plane, are stored in
struct :c:type:`v4l2_plane` instead. In that case,
struct :c:type:`v4l2_buffer` contains an array of plane structures.

+.. note::
+
+ The :ref:`ext_api` version can also be used, and it is
+ preferable when applicable.
+
Dequeued video buffers come with timestamps. The driver decides at which
part of the frame and with which clock the timestamp is taken. Please
see flags in the masks ``V4L2_BUF_FLAG_TIMESTAMP_MASK`` and
diff --git a/Documentation/userspace-api/media/v4l/common.rst b/Documentation/userspace-api/media/v4l/common.rst
index 7d81c58a13cd7..3430e0bdad667 100644
--- a/Documentation/userspace-api/media/v4l/common.rst
+++ b/Documentation/userspace-api/media/v4l/common.rst
@@ -59,6 +59,7 @@ applicable to all devices.
ext-ctrls-detect
fourcc
format
+ ext-api
planar-apis
selection-api
crop
diff --git a/Documentation/userspace-api/media/v4l/dev-capture.rst b/Documentation/userspace-api/media/v4l/dev-capture.rst
index 44d3094093ab6..5077639787d92 100644
--- a/Documentation/userspace-api/media/v4l/dev-capture.rst
+++ b/Documentation/userspace-api/media/v4l/dev-capture.rst
@@ -102,6 +102,11 @@ and :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl, even if :ref:`VIDIOC_S_FMT <VIDIOC
requests and always returns default parameters as :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` does.
:ref:`VIDIOC_TRY_FMT <VIDIOC_G_FMT>` is optional.

+.. note::
+
+ The :ref:`ext_api` version can also be used, and it is
+ preferable when applicable.
+

Reading Images
==============
diff --git a/Documentation/userspace-api/media/v4l/dev-output.rst b/Documentation/userspace-api/media/v4l/dev-output.rst
index e4f2a1d8b0fc7..f8f40c708e49f 100644
--- a/Documentation/userspace-api/media/v4l/dev-output.rst
+++ b/Documentation/userspace-api/media/v4l/dev-output.rst
@@ -99,6 +99,11 @@ and :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl, even if :ref:`VIDIOC_S_FMT <VIDIOC
requests and always returns default parameters as :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` does.
:ref:`VIDIOC_TRY_FMT <VIDIOC_G_FMT>` is optional.

+.. note::
+
+ The :ref:`ext_api` version can also be used, and it is
+ preferable when applicable.
+

Writing Images
==============
diff --git a/Documentation/userspace-api/media/v4l/ext-api.rst b/Documentation/userspace-api/media/v4l/ext-api.rst
new file mode 100644
index 0000000000000..da2a82960d22f
--- /dev/null
+++ b/Documentation/userspace-api/media/v4l/ext-api.rst
@@ -0,0 +1,107 @@
+.. 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
+
+.. _ext_api:
+
+*************
+Extendend API
+*************
+
+Introduction
+============
+
+The Extended Format API was conceived to extend V4L2 capabilities and
+to simplify certain mechanisms.
+It unifies single- vs multi- planar handling,
+brings the concept of pixelformat + modifiers, allows planes to be placed
+in any offset inside a buffer and let userspace to change colorspace
+attributes if supported by the driver.
+
+Data format negotiation and buffer handling works very similar to the classical
+version, thus in this document we'll just mention the main differences.
+
+Data Format Negotiation
+=======================
+
+The API replaces the classical ioctls:
+
+:ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>`, :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>`,
+:ref:`VIDIOC_TRY_FMT <VIDIOC_G_FMT>`
+(with :c:type:`v4l2_format` as the main parameter).
+
+By the extended versions:
+
+:ref:`VIDIOC_G_EXT_PIX_FMT <VIDIOC_G_EXT_PIX_FMT>`,
+:ref:`VIDIOC_S_EXT_PIX_FMT <VIDIOC_G_EXT_PIX_FMT>`,
+:ref:`VIDIOC_TRY_EXT_PIX_FMT <VIDIOC_G_EXT_PIX_FMT>`
+(with :c:type:`v4l2_ext_pix_format` as the main parameter).
+
+For CAPTURE and OUTPUT queues only.
+
+The ``type`` field of struct :c:type:`v4l2_ext_pix_format` only accepts
+``V4L2_BUF_TYPE_VIDEO_CAPTURE`` or ``V4L2_BUF_TYPE_VIDEO_OUTPUT``, and it
+supports multiplanar format through a combination of ``pixelfomat`` and
+``modifier`` fields.
+
+Only the single-planar variants of the pixel formats are valid in the
+``pixelformat`` field.
+To support multi-planar, a modifier should be set in the ``modifier`` field to
+provide more information regarding the memory layout of pixels and number of
+planes.
+
+The ``plane_fmt`` field is an array which holds information by plane using
+the :c:type:`v4l2_plane_ext_pix_format`. When this struct is filled, its
+``sizeimage`` field should be non-zero for all valid planes for a given
+``pixelformat`` + ``modifier`` combination, and zeroed for the invalid ones.
+
+Colospace attributes are not read-only as in the classical version, i.e, they
+can be set by application and drivers will adjust accordingly depending on what
+is supported by the underlying hardware.
+
+Buffers
+=======
+
+The API replaces the classical ioctls:
+
+:ref:`VIDIOC_CREATE_BUFS <VIDIOC_CREATE_BUFS>`
+(with :c:type:`v4l2_create_buffers` as the main parameter),
+:ref:`VIDIOC_QUERYBUF <VIDIOC_QUERYBUF>`, :ref:`VIDIOC_QBUF <VIDIOC_QBUF>`,
+:ref:`VIDIOC_DQBUF <VIDIOC_QBUF>`, :ref:`VIDIOC_PREPARE_BUF <VIDIOC_PREPARE_BUF>`
+(with :c:type:`v4l2_buffer` as the main parameter)
+
+By the extended versions:
+
+:ref:`VIDIOC_EXT_CREATE_BUFS <VIDIOC_EXT_CREATE_BUFS>`
+(with :c:type:`v4l2_ext_create_buffers` as the main parameter),
+:ref:`VIDIOC_EXT_QUERYBUF <VIDIOC_EXT_QUERYBUF>`,
+:ref:`VIDIOC_EXT_QBUF <VIDIOC_EXT_QBUF>`,
+:ref:`VIDIOC_EXT_DQBUF <VIDIOC_EXT_QBUF>`,
+:ref:`VIDIOC_EXT_PREPARE_BUF <VIDIOC_EXT_PREPARE_BUF>`
+(with :c:type:`v4l2_ext_buffer` as the main parameter)
+
+The basic difference between :c:type:`v4l2_create_buffers` and
+:c:type:`v4l2_ext_create_buffers` is that the later have a
+:c:type:`v4l2_ext_pix_format` as the type of the ``format`` field.
+
+Comparing :c:type:`v4l2_ext_buffer` with :c:type:`v4l2_buffer`, in the
+extended version there is a unification of the single-/multi- planar handling
+through the ``planes`` field of type :c:type:`v4l2_ext_plane`.
+
+The :c:type:`v4l2_ext_plane also allows planes to be placed in a given offset
+inside a buffer.
+Planes can be placed in different locations inside the same buffer, or in
+different buffers.
+
+
+.. kernel-doc:: include/uapi/linux/videodev2.h
+ :functions: v4l2_ext_plane
+
+
+.. kernel-doc:: include/uapi/linux/videodev2.h
+ :functions: v4l2_ext_buffer
diff --git a/Documentation/userspace-api/media/v4l/format.rst b/Documentation/userspace-api/media/v4l/format.rst
index e47fc0505727c..b96d26f26793c 100644
--- a/Documentation/userspace-api/media/v4l/format.rst
+++ b/Documentation/userspace-api/media/v4l/format.rst
@@ -28,13 +28,19 @@ format and the driver selects and reports the best the hardware can do
to satisfy the request. Of course applications can also just query the
current selection.

-A single mechanism exists to negotiate all data formats using the
-aggregate struct :c:type:`v4l2_format` and the
+There are two mechanism to negociate data formats:
+
+The first one is using the aggregate struct :c:type:`v4l2_format` and the
:ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` and
:ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctls. Additionally the
:ref:`VIDIOC_TRY_FMT <VIDIOC_G_FMT>` ioctl can be used to examine
what the hardware *could* do, without actually selecting a new data
-format. The data formats supported by the V4L2 API are covered in the
+format.
+
+The second is through the :ref:`ext_api`, please refer to its documentation
+for more information.
+
+The data formats supported by the V4L2 API are covered in the
respective device section in :ref:`devices`. For a closer look at
image formats see :ref:`pixfmt`.

@@ -71,7 +77,9 @@ earlier versions of V4L2. Switching the logical stream or returning into
*may* support a switch using :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>`.

All drivers exchanging data with applications must support the
-:ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` and :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl. Implementation of the
+:ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` and :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl
+or the Extended respective versions (TODO: link).
+Implementation of the
:ref:`VIDIOC_TRY_FMT <VIDIOC_G_FMT>` is highly recommended but optional.

diff --git a/Documentation/userspace-api/media/v4l/user-func.rst b/Documentation/userspace-api/media/v4l/user-func.rst
index bf77c842718e5..67b254812791c 100644
--- a/Documentation/userspace-api/media/v4l/user-func.rst
+++ b/Documentation/userspace-api/media/v4l/user-func.rst
@@ -20,6 +20,7 @@ Function Reference
func-close
func-ioctl
vidioc-create-bufs
+ vidioc-ext-create-bufs
vidioc-cropcap
vidioc-dbg-g-chip-info
vidioc-dbg-g-register
@@ -48,6 +49,7 @@ Function Reference
vidioc-g-ext-ctrls
vidioc-g-fbuf
vidioc-g-fmt
+ vidioc-g-ext-pix-fmt
vidioc-g-frequency
vidioc-g-input
vidioc-g-jpegcomp
@@ -62,8 +64,11 @@ Function Reference
vidioc-log-status
vidioc-overlay
vidioc-prepare-buf
+ vidioc-ext-prepare-buf
vidioc-qbuf
+ vidioc-ext-qbuf
vidioc-querybuf
+ vidioc-ext-querybuf
vidioc-querycap
vidioc-queryctrl
vidioc-query-dv-timings
diff --git a/Documentation/userspace-api/media/v4l/vidioc-ext-create-bufs.rst b/Documentation/userspace-api/media/v4l/vidioc-ext-create-bufs.rst
new file mode 100644
index 0000000000000..67f2c541e4d79
--- /dev/null
+++ b/Documentation/userspace-api/media/v4l/vidioc-ext-create-bufs.rst
@@ -0,0 +1,95 @@
+.. 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_EXT_CREATE_BUFS:
+
+****************************
+ioctl VIDIOC_EXT_CREATE_BUFS
+****************************
+
+Name
+====
+
+VIDIOC_EXT_CREATE_BUFS - Create buffers for Memory Mapped or User Pointer or DMA Buffer I/O
+
+
+Synopsis
+========
+
+.. c:function:: int ioctl( int fd, VIDIOC_EXT_CREATE_BUFS, struct v4l2_ext_create_buffers *argp )
+ :name: VIDIOC_EXT_CREATE_BUFS
+
+
+Arguments
+=========
+
+``fd``
+ File descriptor returned by :ref:`open() <func-open>`.
+
+``argp``
+ Pointer to struct :c:type:`v4l2_ext_create_buffers`.
+
+
+Description
+===========
+
+This ioctl is used to create buffers for :ref:`memory mapped <mmap>`
+or :ref:`user pointer <userp>` or :ref:`DMA buffer <dmabuf>` I/O.
+This ioctl can be called multiple times to
+create buffers of different sizes.
+
+To allocate the device buffers applications must initialize the relevant
+fields of the struct :c:type:`v4l2_ext_create_buffers` structure. The
+``count`` field must be set to the number of requested buffers, the
+``memory`` field specifies the requested I/O method and the ``reserved``
+array must be zeroed.
+
+The ``format`` field specifies the image format that the buffers must be
+able to handle. The application has to fill in this struct
+:c:type:`v4l2_format`. Usually this will be done using the
+:ref:`VIDIOC_TRY_EXT_PIX_FMT <VIDIOC_G_EXT_PIX_FMT>` or
+:ref:`VIDIOC_G_EXT_PIX_FMT <VIDIOC_G_EXT_PIX_FMT>` ioctls to ensure that the
+requested format is supported by the driver.
+The driver may return an error if the size(s) are not supported by the
+hardware (usually because they are too small).
+
+The driver can create a memory buffer per plane, or a single memory buffer
+containing all the planes, with a minimum size according to the size
+defined by the ``format.plane_fmt[i].sizeimage`` field.
+Usually if the ``format.plane_fmt[i].sizeimage``
+field is less than the minimum required for the given format, then an
+error will be returned since drivers will typically not allow this. If
+it is larger, then the value will be used as-is. In other words, the
+driver may reject the requested size, but if it is accepted the driver
+will use it unchanged.
+
+When the ioctl is called with a pointer to this structure the driver
+will attempt to allocate up to the requested number of buffers and store
+the actual number allocated and the starting index in the ``count`` and
+the ``index`` fields respectively. On return ``count`` can be smaller
+than the number requested.
+
+
+.. kernel-doc:: include/uapi/linux/videodev2.h
+ :functions: v4l2_ext_create_buffers
+
+
+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.
+
+ENOMEM
+ No memory to allocate buffers for :ref:`memory mapped <mmap>` I/O.
+
+EINVAL
+ The buffer type (``format.type`` field), requested I/O method
+ (``memory``) or format (``format`` field) is not valid.
diff --git a/Documentation/userspace-api/media/v4l/vidioc-ext-prepare-buf.rst b/Documentation/userspace-api/media/v4l/vidioc-ext-prepare-buf.rst
new file mode 100644
index 0000000000000..88e4b57121254
--- /dev/null
+++ b/Documentation/userspace-api/media/v4l/vidioc-ext-prepare-buf.rst
@@ -0,0 +1,62 @@
+.. 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_EXT_PREPARE_BUF:
+
+****************************
+ioctl VIDIOC_EXT_PREPARE_BUF
+****************************
+
+Name
+====
+
+VIDIOC_EXT_PREPARE_BUF - Prepare a buffer for I/O
+
+
+Synopsis
+========
+
+.. c:function:: int ioctl( int fd, VIDIOC_EXT_PREPARE_BUF, struct v4l2_ext_buffer *argp )
+ :name: VIDIOC_EXT_PREPARE_BUF
+
+
+Arguments
+=========
+
+``fd``
+ File descriptor returned by :ref:`open() <func-open>`.
+
+``argp``
+ Pointer to struct :c:type:`v4l2_ext_buffer`.
+
+
+Description
+===========
+
+Applications can optionally call the :ref:`VIDIOC_EXT_PREPARE_BUF` ioctl to
+pass ownership of the buffer to the driver before actually enqueuing it,
+using the :ref:`VIDIOC_EXT_QBUF <VIDIOC_EXT_QBUF>` ioctl, and to prepare it for future I/O. Such
+preparations may include cache invalidation or cleaning. Performing them
+in advance saves time during the actual I/O.
+
+
+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.
+
+EBUSY
+ File I/O is in progress.
+
+EINVAL
+ The buffer ``type`` is not supported, or the ``index`` is out of
+ bounds, or no buffers have been allocated yet, or the ``userptr`` or
+ ``length`` are invalid.
diff --git a/Documentation/userspace-api/media/v4l/vidioc-ext-qbuf.rst b/Documentation/userspace-api/media/v4l/vidioc-ext-qbuf.rst
new file mode 100644
index 0000000000000..083e106cf6bad
--- /dev/null
+++ b/Documentation/userspace-api/media/v4l/vidioc-ext-qbuf.rst
@@ -0,0 +1,204 @@
+.. 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_EXT_QBUF:
+
+***************************************
+ioctl VIDIOC_EXT_QBUF, VIDIOC_EXT_DQBUF
+***************************************
+
+Name
+====
+
+VIDIOC_EXT_QBUF - VIDIOC_EXT_DQBUF - Exchange a buffer with the driver
+
+
+Synopsis
+========
+
+.. c:function:: int ioctl( int fd, VIDIOC_EXT_QBUF, struct v4l2_ext_buffer *argp )
+ :name: VIDIOC_EXT_QBUF
+
+.. c:function:: int ioctl( int fd, VIDIOC_EXT_DQBUF, struct v4l2_ext_buffer *argp )
+ :name: VIDIOC_EXT_DQBUF
+
+
+Arguments
+=========
+
+``fd``
+ File descriptor returned by :ref:`open() <func-open>`.
+
+``argp``
+ Pointer to struct :c:type:`v4l2_ext_buffer`.
+
+
+Description
+===========
+
+Applications call the ``VIDIOC_EXT_QBUF`` ioctl to enqueue an empty
+(capturing) or filled (output) buffer in the driver's incoming queue.
+The semantics depend on the selected I/O method.
+
+To enqueue a buffer applications set the ``type`` field of a struct
+:c:type:`v4l2_ext_buffer` to the same buffer type as was
+previously used with struct :c:type:`v4l2_ext_pix_format` ``type``.
+Applications must also set the ``index`` field. Valid index numbers
+range from zero to the number of buffers allocated with
+:ref:`VIDIOC_EXT_CREATE_BUFS` (struct
+:c:type:`v4l2_ext_create_buffers` ``count``) minus
+one. The contents of the struct :c:type:`v4l2_ext_buffer` returned
+by a :ref:`VIDIOC_EXT_QUERYBUF` ioctl will do as well.
+When the buffer is intended for output (``type`` is
+``V4L2_BUF_TYPE_VIDEO_OUTPUT``) applications must also initialize the
+``timestamp`` fields and the ``planes[i].plane_length`` for each valid plane,
+and invalid ones must be set as zero.
+see :ref:`buffer` for details. Applications must also set ``flags`` to 0. The
+``reserved`` field must be set to 0.
+
+To enqueue a :ref:`memory mapped <mmap>` buffer applications set the
+``planes[i].memory`` field to ``V4L2_MEMORY_MMAP`` in all the valid planes,
+and invalid ones must be set as zero.
+When ``VIDIOC_EXT_QBUF`` is called
+with a pointer to this structure the driver sets the
+``V4L2_BUF_FLAG_MAPPED`` and ``V4L2_BUF_FLAG_QUEUED`` flags and clears
+the ``V4L2_BUF_FLAG_DONE`` flag in the ``flags`` field, or it returns an
+``EINVAL`` error code.
+
+To enqueue a :ref:`user pointer <userp>` buffer applications set the
+``planes[i].memory`` field to ``V4L2_MEMORY_USERPTR`` in all the valid planes,
+and invalid ones must be set as zero, the ``planes[i].m.userptr`` field to the
+address of the buffer,``planes[i].buffer_length`` to the size of the memory
+buffer, ``planes[i].plane_length`` to the size that should be used by the plane,
+and ``planes[i].offset`` of the plane in the memory buffer.
+
+When ``VIDIOC_EXT_QBUF`` is called with a pointer to this structure
+the driver sets the ``V4L2_BUF_FLAG_QUEUED`` flag and clears the
+``V4L2_BUF_FLAG_MAPPED`` and ``V4L2_BUF_FLAG_DONE`` flags in the
+``flags`` field, or it returns an error code. This ioctl locks the
+memory pages of the buffer in physical memory, they cannot be swapped
+out to disk. Buffers remain locked until dequeued, until the
+:ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>` or
+:ref:`VIDIOC_EXT_CREATE_BUFS` ioctl is called, or until the
+device is closed.
+
+To enqueue a :ref:`DMABUF <dmabuf>` buffer applications set the
+``planes[i].memory`` field to ``V4L2_MEMORY_DMABUF`` in all the valid planes,
+and invalid ones must be set as zero, the ``planes[i].m.fd`` field to a
+file descriptor associated with a DMABUF buffer.,``planes[i].buffer_length`` to
+the size of the memory buffer, ``planes[i].plane_length`` to the size that
+should be used by the plane, and ``planes[i].offset`` of the plane in the memory buffer.
+When ``VIDIOC_EXT_QBUF`` is called with a pointer to this structure the driver
+sets the ``V4L2_BUF_FLAG_QUEUED`` flag and clears the
+``V4L2_BUF_FLAG_MAPPED`` and ``V4L2_BUF_FLAG_DONE`` flags in the
+``flags`` field, or it returns an error code. This ioctl locks the
+buffer. Locking a buffer means passing it to a driver for a hardware
+access (usually DMA). If an application accesses (reads/writes) a locked
+buffer then the result is undefined. Buffers remain locked until
+dequeued, until the :ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>` or
+:ref:`VIDIOC_EXT_CREATE_BUFS` ioctl is called, or until the
+device is closed.
+
+The ``request_fd`` field can be used with the ``VIDIOC_EXT_QBUF`` ioctl to specify
+the file descriptor of a :ref:`request <media-request-api>`, if requests are
+in use. Setting it means that the buffer will not be passed to the driver
+until the request itself is queued. Also, the driver will apply any
+settings associated with the request for this buffer. This field will
+be ignored unless the ``V4L2_BUF_FLAG_REQUEST_FD`` flag is set.
+If the device does not support requests, then ``EBADR`` will be returned.
+If requests are supported but an invalid request file descriptor is given,
+then ``EINVAL`` will be returned.
+
+.. caution::
+ It is not allowed to mix queuing requests with queuing buffers directly.
+ ``EBUSY`` will be returned if the first buffer was queued directly and
+ then the application tries to queue a request, or vice versa. After
+ closing the file descriptor, calling
+ :ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>` or calling :ref:`VIDIOC_EXT_CREATE_BUFS`
+ the check for this will be reset.
+
+ For :ref:`memory-to-memory devices <mem2mem>` you can specify the
+ ``request_fd`` only for output buffers, not for capture buffers. Attempting
+ to specify this for a capture buffer will result in an ``EBADR`` error.
+
+Applications call the ``VIDIOC_EXT_DQBUF`` ioctl to dequeue a filled
+(capturing) or displayed (output) buffer from the driver's outgoing
+queue. They just set the ``type``, ``planes[i].memory`` and ``reserved`` fields of
+a struct :c:type:`v4l2_ext_buffer` as above, when
+``VIDIOC_EXT_DQBUF`` is called with a pointer to this structure the driver
+fills the remaining fields or returns an error code. The driver may also
+set ``V4L2_BUF_FLAG_ERROR`` in the ``flags`` field. It indicates a
+non-critical (recoverable) streaming error. In such case the application
+may continue as normal, but should be aware that data in the dequeued
+buffer might be corrupted. When using the multi-planar API, the planes
+array must be passed in as well.
+
+If the application sets the ``memory`` field to ``V4L2_MEMORY_DMABUF`` to
+dequeue a :ref:`DMABUF <dmabuf>` buffer, the driver fills the ``m.fd`` field
+with a file descriptor numerically the same as the one given to ``VIDIOC_EXT_QBUF``
+when the buffer was enqueued. No new file descriptor is created at dequeue time
+and the value is only for the application convenience.
+
+By default ``VIDIOC_EXT_DQBUF`` blocks when no buffer is in the outgoing
+queue. When the ``O_NONBLOCK`` flag was given to the
+:ref:`open() <func-open>` function, ``VIDIOC_EXT_DQBUF`` returns
+immediately with an ``EAGAIN`` error code when no buffer is available.
+
+
+.. kernel-doc:: include/uapi/linux/videodev2.h
+ :functions: v4l2_ext_buffers
+
+
+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.
+
+EAGAIN
+ Non-blocking I/O has been selected using ``O_NONBLOCK`` and no
+ buffer was in the outgoing queue.
+
+EINVAL
+ The buffer ``type`` is not supported, or the ``index`` is out of
+ bounds, or no buffers have been allocated yet, or the ``userptr`` or
+ ``length`` are invalid, or the ``V4L2_BUF_FLAG_REQUEST_FD`` flag was
+ set but the the given ``request_fd`` was invalid, or ``m.fd`` was
+ an invalid DMABUF file descriptor.
+
+EIO
+ ``VIDIOC_EXT_DQBUF`` failed due to an internal error. Can also indicate
+ temporary problems like signal loss.
+
+ .. note::
+
+ The driver might dequeue an (empty) buffer despite returning
+ an error, or even stop capturing. Reusing such buffer may be unsafe
+ though and its details (e.g. ``index``) may not be returned either.
+ It is recommended that drivers indicate recoverable errors by setting
+ the ``V4L2_BUF_FLAG_ERROR`` and returning 0 instead. In that case the
+ application should be able to safely reuse the buffer and continue
+ streaming.
+
+EPIPE
+ ``VIDIOC_EXT_DQBUF`` returns this on an empty capture queue for mem2mem
+ codecs if a buffer with the ``V4L2_BUF_FLAG_LAST`` was already
+ dequeued and no new buffers are expected to become available.
+
+EBADR
+ The ``V4L2_BUF_FLAG_REQUEST_FD`` flag was set but the device does not
+ support requests for the given buffer type, or
+ the ``V4L2_BUF_FLAG_REQUEST_FD`` flag was not set but the device requires
+ that the buffer is part of a request.
+
+EBUSY
+ The first buffer was queued via a request, but the application now tries
+ to queue it directly, or vice versa (it is not permitted to mix the two
+ APIs).
diff --git a/Documentation/userspace-api/media/v4l/vidioc-ext-querybuf.rst b/Documentation/userspace-api/media/v4l/vidioc-ext-querybuf.rst
new file mode 100644
index 0000000000000..f2a12017253f6
--- /dev/null
+++ b/Documentation/userspace-api/media/v4l/vidioc-ext-querybuf.rst
@@ -0,0 +1,79 @@
+.. 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_EXT_QUERYBUF:
+
+*************************
+ioctl VIDIOC_EXT_QUERYBUF
+*************************
+
+Name
+====
+
+VIDIOC_EXT_QUERYBUF - Query the status of a buffer
+
+
+Synopsis
+========
+
+.. c:function:: int ioctl( int fd, VIDIOC_EXT_QUERYBUF, struct v4l2_ext_buffer *argp )
+ :name: VIDIOC_EXT_QUERYBUF
+
+
+Arguments
+=========
+
+``fd``
+ File descriptor returned by :ref:`open() <func-open>`.
+
+``argp``
+ Pointer to struct :c:type:`v4l2_ext_buffer`.
+
+
+Description
+===========
+
+This ioctl is part of the :ref:`streaming <mmap>` I/O method. It can
+be used to query the status of a buffer at any time after buffers have
+been allocated with the :ref:`VIDIOC_EXT_CREATE_BUFS` ioctl.
+
+Applications set the ``type`` field of a struct
+:c:type:`v4l2_ext_buffer` to the same buffer type as was
+previously used with struct :c:type:`v4l2_ext_pix_format` ``type``,
+and the ``index`` field. Valid index numbers range from zero to the
+number of buffers allocated with
+:ref:`VIDIOC_EXT_CREATE_BUFS` (struct
+:c:type:`v4l2_ext_create_buffers` ``count``) minus
+one. The ``reserved`` field must be set to 0.
+
+In the ``flags`` field the ``V4L2_BUF_FLAG_MAPPED``,
+``V4L2_BUF_FLAG_PREPARED``, ``V4L2_BUF_FLAG_QUEUED`` and
+``V4L2_BUF_FLAG_DONE`` flags will be valid. The ``planes.memory`` fields will be
+set to the current I/O method for each plane.
+
+For every valid plane, an entry in ``planes`` will be filled, and zeroed for
+invalid ones. ``planes[i].buffer_length`` is the size of the memory buffer
+which contains the plane, ``planes[i].plane_length`` is the length of the plane,
+and ``planes[i].offset` is where the plane is placed in the memory buffer.
+
+The size of the ``planes`` array can be calculated by the number of sequential
+planes with ``planes[i].buffer_length`` that differs from zero up to the max
+size of the array.
+
+
+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 buffer ``type`` is not supported, or the ``index`` is out of
+ bounds.
diff --git a/Documentation/userspace-api/media/v4l/vidioc-g-ext-pix-fmt.rst b/Documentation/userspace-api/media/v4l/vidioc-g-ext-pix-fmt.rst
new file mode 100644
index 0000000000000..008e6c98a88a5
--- /dev/null
+++ b/Documentation/userspace-api/media/v4l/vidioc-g-ext-pix-fmt.rst
@@ -0,0 +1,117 @@
+.. 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_EXT_PIX_FMT:
+
+************************************************************************
+ioctl VIDIOC_G_EXT_PIX_FMT, VIDIOC_S_EXT_PIX_FMT, VIDIOC_TRY_EXT_PIX_FMT
+************************************************************************
+
+Name
+====
+
+VIDIOC_G_EXT_PIX_FMT - VIDIOC_S_EXT_PIX_FMT - VIDIOC_TRY_EXT_PIX_FMT - Get or set the data format, try a format
+
+
+Synopsis
+========
+
+.. c:function:: int ioctl( int fd, VIDIOC_G_EXT_PIX_FMT, struct v4l2_ext_pix_format *argp )
+ :name: VIDIOC_G_EXT_PIX_FMT
+
+.. c:function:: int ioctl( int fd, VIDIOC_S_EXT_PIX_FMT, struct v4l2_ext_pix_format *argp )
+ :name: VIDIOC_S_EXT_PIX_FMT
+
+.. c:function:: int ioctl( int fd, VIDIOC_TRY_EXT_PIX_FMT, struct v4l2_ext_pix_format *argp )
+ :name: VIDIOC_TRY_EXT_PIX_FMT
+
+Arguments
+=========
+
+``fd``
+ File descriptor returned by :ref:`open() <func-open>`.
+
+``argp``
+ Pointer to struct :c:type:`v4l2_ext_pix_format`.
+
+
+Description
+===========
+
+These ioctls are used to negotiate the format of data (typically image
+format) exchanged between driver and application.
+
+To query the current parameters applications set the ``type`` field of a
+struct :c:type:`v4l2_ext_pix_format` to ``V4L2_BUF_TYPE_VIDEO_CAPTURE`` or
+``V4L2_BUF_TYPE_VIDEO_OUTPUT``, all the other types are invalid in this API,
+and multiplanar is supported through modifiers.
+
+When the application calls the
+:ref:`VIDIOC_G_EXT_PIX_FMT <VIDIOC_G_EXT_PIX_FMT>` ioctl with a pointer to this
+structure the driver fills the other members.
+When the requested buffer type is not supported drivers return
+an ``EINVAL`` error code.
+
+To change the current format parameters applications initialize all
+the fields in the struct.
+For details see the documentation of the various devices types in
+:ref:`devices`. Good practice is to query the current parameters
+first, and to modify only those parameters not suitable for the
+application. When the application calls the :ref:`VIDIOC_S_EXT_PIX_FMT <VIDIOC_G_EXT_PIX_FMT>` ioctl with
+a pointer to a struct :c:type:`v4l2_ext_pix_format` structure the driver
+checks and adjusts the parameters against hardware abilities. Drivers
+should not return an error code unless the ``type`` field is invalid,
+this is a mechanism to fathom device capabilities and to approach
+parameters acceptable for both the application and driver. On success
+the driver may program the hardware, allocate resources and generally
+prepare for data exchange. Finally the :ref:`VIDIOC_S_EXT_PIX_FMT <VIDIOC_G_EXT_PIX_FMT>` ioctl returns
+the current format parameters as :ref:`VIDIOC_G_EXT_PIX_FMT <VIDIOC_G_EXT_PIX_FMT>` does. Very simple,
+inflexible devices may even ignore all input and always return the
+default parameters. However all V4L2 devices exchanging data with the
+application must implement the :ref:`VIDIOC_G_EXT_PIX_FMT <VIDIOC_G_EXT_PIX_FMT>` and :ref:`VIDIOC_S_EXT_PIX_FMT <VIDIOC_G_EXT_PIX_FMT>`
+ioctl. When the requested buffer type is not supported drivers return an
+EINVAL error code on a :ref:`VIDIOC_S_EXT_PIX_FMT <VIDIOC_G_EXT_PIX_FMT>` attempt. When I/O is already in
+progress or the resource is not available for other reasons drivers
+return the ``EBUSY`` error code.
+
+The :ref:`VIDIOC_TRY_EXT_PIX_FMT <VIDIOC_G_EXT_PIX_FMT>` ioctl is equivalent to :ref:`VIDIOC_S_EXT_PIX_FMT <VIDIOC_G_EXT_PIX_FMT>` with one
+exception: it does not change driver state. It can also be called at any
+time, never returning ``EBUSY``. This function is provided to negotiate
+parameters, to learn about hardware limitations, without disabling I/O
+or possibly time consuming hardware preparations. Although strongly
+recommended drivers are not required to implement this ioctl.
+
+The format as returned by :ref:`VIDIOC_TRY_EXT_PIX_FMT <VIDIOC_G_EXT_PIX_FMT>` must be identical to what
+:ref:`VIDIOC_S_EXT_PIX_FMT <VIDIOC_G_EXT_PIX_FMT>` returns for the same input or output.
+
+
+.. kernel-doc:: include/uapi/linux/videodev2.h
+ :functions: v4l2_plane_ext_pix_format
+
+
+.. kernel-doc:: include/uapi/linux/videodev2.h
+ :functions: v4l2_ext_pix_format
+
+
+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 struct :c:type:`v4l2_ext_pix_format` ``type`` field is
+ invalid or the requested buffer type not supported.
+
+EBUSY
+ The device is busy and cannot change the format. This could be
+ because or the device is streaming or buffers are allocated or
+ queued to the driver. Relevant for :ref:`VIDIOC_S_EXT_PIX_FMT
+ <VIDIOC_G_EXT_PIX_FMT>` only.
--
2.28.0.rc2