Adding upstream version 6.1.76.upstream/6.1.76upstream

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

1 files changed, 181 insertions, 0 deletions

diff --git a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
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+.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
+.. c:namespace:: V4L
+
+.. _VIDIOC_REQBUFS:
+
+********************
+ioctl VIDIOC_REQBUFS
+********************
+
+Name
+====
+
+VIDIOC_REQBUFS - Initiate Memory Mapping, User Pointer I/O or DMA buffer I/O
+
+Synopsis
+========
+
+.. c:macro:: VIDIOC_REQBUFS
+
+``int ioctl(int fd, VIDIOC_REQBUFS, struct v4l2_requestbuffers *argp)``
+
+Arguments
+=========
+
+``fd``
+    File descriptor returned by :c:func:`open()`.
+
+``argp``
+    Pointer to struct :c:type:`v4l2_requestbuffers`.
+
+Description
+===========
+
+This ioctl is used to initiate :ref:`memory mapped <mmap>`,
+:ref:`user pointer <userp>` or :ref:`DMABUF <dmabuf>` based I/O.
+Memory mapped buffers are located in device memory and must be allocated
+with this ioctl before they can be mapped into the application's address
+space. User buffers are allocated by applications themselves, and this
+ioctl is merely used to switch the driver into user pointer I/O mode and
+to setup some internal structures. Similarly, DMABUF buffers are
+allocated by applications through a device driver, and this ioctl only
+configures the driver into DMABUF I/O mode without performing any direct
+allocation.
+
+To allocate device buffers applications initialize all fields of the
+struct :c:type:`v4l2_requestbuffers` structure. They set the ``type``
+field to the respective stream or buffer type, the ``count`` field to
+the desired number of buffers, ``memory`` must be set to the requested
+I/O method and the ``reserved`` array must be zeroed. When the ioctl is
+called with a pointer to this structure the driver will attempt to
+allocate the requested number of buffers and it stores the actual number
+allocated in the ``count`` field. It can be smaller than the number
+requested, even zero, when the driver runs out of free memory. A larger
+number is also possible when the driver requires more buffers to
+function correctly. For example video output requires at least two
+buffers, one displayed and one filled by the application.
+
+When the I/O method is not supported the ioctl returns an ``EINVAL`` error
+code.
+
+Applications can call :ref:`VIDIOC_REQBUFS` again to change the number of
+buffers. Note that if any buffers are still mapped or exported via DMABUF,
+then :ref:`VIDIOC_REQBUFS` can only succeed if the
+``V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS`` capability is set. Otherwise
+:ref:`VIDIOC_REQBUFS` will return the ``EBUSY`` error code.
+If ``V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS`` is set, then these buffers are
+orphaned and will be freed when they are unmapped or when the exported DMABUF
+fds are closed. A ``count`` value of zero frees or orphans all buffers, after
+aborting or finishing any DMA in progress, an implicit
+:ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>`.
+
+.. c:type:: v4l2_requestbuffers
+
+.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}|
+
+.. flat-table:: struct v4l2_requestbuffers
+    :header-rows:  0
+    :stub-columns: 0
+    :widths:       1 1 2
+
+    * - __u32
+      - ``count``
+      - The number of buffers requested or granted.
+    * - __u32
+      - ``type``
+      - Type of the stream or buffers, this is the same as the struct
+	:c:type:`v4l2_format` ``type`` field. See
+	:c:type:`v4l2_buf_type` for valid values.
+    * - __u32
+      - ``memory``
+      - Applications set this field to ``V4L2_MEMORY_MMAP``,
+	``V4L2_MEMORY_DMABUF`` or ``V4L2_MEMORY_USERPTR``. See
+	:c:type:`v4l2_memory`.
+    * - __u32
+      - ``capabilities``
+      - Set by the driver. If 0, then the driver doesn't support
+        capabilities. In that case all you know is that the driver is
+	guaranteed to support ``V4L2_MEMORY_MMAP`` and *might* support
+	other :c:type:`v4l2_memory` types. It will not support any other
+	capabilities.
+
+	If you want to query the capabilities with a minimum of side-effects,
+	then this can be called with ``count`` set to 0, ``memory`` set to
+	``V4L2_MEMORY_MMAP`` and ``type`` set to the buffer type. This will
+	free any previously allocated buffers, so this is typically something
+	that will be done at the start of the application.
+    * - __u8
+      - ``flags``
+      - Specifies additional buffer management attributes.
+	See :ref:`memory-flags`.
+    * - __u8
+      - ``reserved``\ [3]
+      - Reserved for future extensions.
+
+.. _v4l2-buf-capabilities:
+.. _V4L2-BUF-CAP-SUPPORTS-MMAP:
+.. _V4L2-BUF-CAP-SUPPORTS-USERPTR:
+.. _V4L2-BUF-CAP-SUPPORTS-DMABUF:
+.. _V4L2-BUF-CAP-SUPPORTS-REQUESTS:
+.. _V4L2-BUF-CAP-SUPPORTS-ORPHANED-BUFS:
+.. _V4L2-BUF-CAP-SUPPORTS-M2M-HOLD-CAPTURE-BUF:
+.. _V4L2-BUF-CAP-SUPPORTS-MMAP-CACHE-HINTS:
+
+.. raw:: latex
+
+   \footnotesize
+
+.. tabularcolumns:: |p{8.1cm}|p{2.2cm}|p{7.0cm}|
+
+.. cssclass:: longtable
+
+.. flat-table:: V4L2 Buffer Capabilities Flags
+    :header-rows:  0
+    :stub-columns: 0
+    :widths:       3 1 4
+
+    * - ``V4L2_BUF_CAP_SUPPORTS_MMAP``
+      - 0x00000001
+      - This buffer type supports the ``V4L2_MEMORY_MMAP`` streaming mode.
+    * - ``V4L2_BUF_CAP_SUPPORTS_USERPTR``
+      - 0x00000002
+      - This buffer type supports the ``V4L2_MEMORY_USERPTR`` streaming mode.
+    * - ``V4L2_BUF_CAP_SUPPORTS_DMABUF``
+      - 0x00000004
+      - This buffer type supports the ``V4L2_MEMORY_DMABUF`` streaming mode.
+    * - ``V4L2_BUF_CAP_SUPPORTS_REQUESTS``
+      - 0x00000008
+      - This buffer type supports :ref:`requests <media-request-api>`.
+    * - ``V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS``
+      - 0x00000010
+      - The kernel allows calling :ref:`VIDIOC_REQBUFS` while buffers are still
+        mapped or exported via DMABUF. These orphaned buffers will be freed
+        when they are unmapped or when the exported DMABUF fds are closed.
+    * - ``V4L2_BUF_CAP_SUPPORTS_M2M_HOLD_CAPTURE_BUF``
+      - 0x00000020
+      - Only valid for stateless decoders. If set, then userspace can set the
+        ``V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF`` flag to hold off on returning the
+	capture buffer until the OUTPUT timestamp changes.
+    * - ``V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS``
+      - 0x00000040
+      - This capability is set by the driver to indicate that the queue supports
+        cache and memory management hints. However, it's only valid when the
+        queue is used for :ref:`memory mapping <mmap>` streaming I/O. See
+        :ref:`V4L2_BUF_FLAG_NO_CACHE_INVALIDATE <V4L2-BUF-FLAG-NO-CACHE-INVALIDATE>`,
+        :ref:`V4L2_BUF_FLAG_NO_CACHE_CLEAN <V4L2-BUF-FLAG-NO-CACHE-CLEAN>` and
+        :ref:`V4L2_MEMORY_FLAG_NON_COHERENT <V4L2-MEMORY-FLAG-NON-COHERENT>`.
+
+.. raw:: latex
+
+   \normalsize
+
+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 (``type`` field) or the requested I/O method
+    (``memory``) is not supported.