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diff --git a/Documentation/media/uapi/v4l/vidioc-reqbufs.rst b/Documentation/media/uapi/v4l/vidioc-reqbufs.rst deleted file mode 100644 index d0c643db477a..000000000000 --- a/Documentation/media/uapi/v4l/vidioc-reqbufs.rst +++ /dev/null @@ -1,169 +0,0 @@ -.. 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/media/uapi/fdl-appendix.rst. -.. -.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections - -.. _VIDIOC_REQBUFS: - -******************** -ioctl VIDIOC_REQBUFS -******************** - -Name -==== - -VIDIOC_REQBUFS - Initiate Memory Mapping, User Pointer I/O or DMA buffer I/O - - -Synopsis -======== - -.. c:function:: int ioctl( int fd, VIDIOC_REQBUFS, struct v4l2_requestbuffers *argp ) - :name: VIDIOC_REQBUFS - - -Arguments -========= - -``fd`` - File descriptor returned by :ref:`open() <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{8.7cm}| - -.. 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 others - 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. - * - __u32 - - ``reserved``\ [1] - - A place holder for future extensions. Drivers and applications - must set the array to zero. - -.. tabularcolumns:: |p{6.1cm}|p{2.2cm}|p{8.7cm}| - -.. _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: - -.. 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. - -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. |