Adding upstream version 4.19.249.upstream/4.19.249upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 122 insertions, 0 deletions

diff --git a/Documentation/media/uapi/v4l/vidioc-create-bufs.rst b/Documentation/media/uapi/v4l/vidioc-create-bufs.rst
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+.. -*- coding: utf-8; mode: rst -*-
+
+.. _VIDIOC_CREATE_BUFS:
+
+************************
+ioctl VIDIOC_CREATE_BUFS
+************************
+
+Name
+====
+
+VIDIOC_CREATE_BUFS - Create buffers for Memory Mapped or User Pointer or DMA Buffer I/O
+
+
+Synopsis
+========
+
+.. c:function:: int ioctl( int fd, VIDIOC_CREATE_BUFS, struct v4l2_create_buffers *argp )
+    :name: VIDIOC_CREATE_BUFS
+
+
+Arguments
+=========
+
+``fd``
+    File descriptor returned by :ref:`open() <func-open>`.
+
+``argp``
+    Pointer to struct :c:type:`v4l2_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. It
+can be used as an alternative or in addition to the
+:ref:`VIDIOC_REQBUFS` ioctl, when a tighter control
+over buffers is required. 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_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_FMT <VIDIOC_G_FMT>` or
+:ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` ioctls to ensure that the
+requested format is supported by the driver. Based on the format's
+``type`` field the requested buffer size (for single-planar) or plane
+sizes (for multi-planar formats) will be used for the allocated buffers.
+The driver may return an error if the size(s) are not supported by the
+hardware (usually because they are too small).
+
+The buffers created by this ioctl will have as minimum size the size
+defined by the ``format.pix.sizeimage`` field (or the corresponding
+fields for other format types). Usually if the ``format.pix.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.
+
+
+.. c:type:: v4l2_create_buffers
+
+.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
+
+.. flat-table:: struct v4l2_create_buffers
+    :header-rows:  0
+    :stub-columns: 0
+    :widths:       1 1 2
+
+    * - __u32
+      - ``index``
+      - The starting buffer index, returned by the driver.
+    * - __u32
+      - ``count``
+      - The number of buffers requested or granted. If count == 0, then
+	:ref:`VIDIOC_CREATE_BUFS` will set ``index`` to the current number of
+	created buffers, and it will check the validity of ``memory`` and
+	``format.type``. If those are invalid -1 is returned and errno is
+	set to ``EINVAL`` error code, otherwise :ref:`VIDIOC_CREATE_BUFS` returns
+	0. It will never set errno to ``EBUSY`` error code in this particular
+	case.
+    * - __u32
+      - ``memory``
+      - Applications set this field to ``V4L2_MEMORY_MMAP``,
+	``V4L2_MEMORY_DMABUF`` or ``V4L2_MEMORY_USERPTR``. See
+	:c:type:`v4l2_memory`
+    * - struct :c:type:`v4l2_format`
+      - ``format``
+      - Filled in by the application, preserved by the driver.
+    * - __u32
+      - ``reserved``\ [8]
+      - A place holder for future extensions. Drivers and applications
+	must set the array to zero.
+
+
+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.