^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1) .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 2) .. c:namespace:: V4L
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 3)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 4) .. _VIDIOC_CREATE_BUFS:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 5)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 6) ************************
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 7) ioctl VIDIOC_CREATE_BUFS
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 8) ************************
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 9)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 10) Name
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 11) ====
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 12)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 13) VIDIOC_CREATE_BUFS - Create buffers for Memory Mapped or User Pointer or DMA Buffer I/O
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 14)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 15) Synopsis
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 16) ========
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 17)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 18) .. c:macro:: VIDIOC_CREATE_BUFS
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 19)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 20) ``int ioctl(int fd, VIDIOC_CREATE_BUFS, struct v4l2_create_buffers *argp)``
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 21)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 22) Arguments
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 23) =========
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 24)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 25) ``fd``
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 26) File descriptor returned by :c:func:`open()`.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 27)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 28) ``argp``
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 29) Pointer to struct :c:type:`v4l2_create_buffers`.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 30)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 31) Description
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 32) ===========
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 33)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 34) This ioctl is used to create buffers for :ref:`memory mapped <mmap>`
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 35) or :ref:`user pointer <userp>` or :ref:`DMA buffer <dmabuf>` I/O. It
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 36) can be used as an alternative or in addition to the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 37) :ref:`VIDIOC_REQBUFS` ioctl, when a tighter control
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 38) over buffers is required. This ioctl can be called multiple times to
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 39) create buffers of different sizes.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 40)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 41) To allocate the device buffers applications must initialize the relevant
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 42) fields of the struct :c:type:`v4l2_create_buffers` structure. The
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 43) ``count`` field must be set to the number of requested buffers, the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 44) ``memory`` field specifies the requested I/O method and the ``reserved``
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 45) array must be zeroed.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 46)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 47) The ``format`` field specifies the image format that the buffers must be
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 48) able to handle. The application has to fill in this struct
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 49) :c:type:`v4l2_format`. Usually this will be done using the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 50) :ref:`VIDIOC_TRY_FMT <VIDIOC_G_FMT>` or
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 51) :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` ioctls to ensure that the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 52) requested format is supported by the driver. Based on the format's
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 53) ``type`` field the requested buffer size (for single-planar) or plane
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 54) sizes (for multi-planar formats) will be used for the allocated buffers.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 55) The driver may return an error if the size(s) are not supported by the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 56) hardware (usually because they are too small).
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 57)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 58) The buffers created by this ioctl will have as minimum size the size
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 59) defined by the ``format.pix.sizeimage`` field (or the corresponding
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 60) fields for other format types). Usually if the ``format.pix.sizeimage``
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 61) field is less than the minimum required for the given format, then an
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 62) error will be returned since drivers will typically not allow this. If
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 63) it is larger, then the value will be used as-is. In other words, the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 64) driver may reject the requested size, but if it is accepted the driver
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 65) will use it unchanged.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 66)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 67) When the ioctl is called with a pointer to this structure the driver
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 68) will attempt to allocate up to the requested number of buffers and store
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 69) the actual number allocated and the starting index in the ``count`` and
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 70) the ``index`` fields respectively. On return ``count`` can be smaller
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 71) than the number requested.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 72)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 73) .. c:type:: v4l2_create_buffers
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 74)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 75) .. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 76)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 77) .. flat-table:: struct v4l2_create_buffers
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 78) :header-rows: 0
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 79) :stub-columns: 0
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 80) :widths: 1 1 2
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 81)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 82) * - __u32
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 83) - ``index``
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 84) - The starting buffer index, returned by the driver.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 85) * - __u32
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 86) - ``count``
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 87) - The number of buffers requested or granted. If count == 0, then
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 88) :ref:`VIDIOC_CREATE_BUFS` will set ``index`` to the current number of
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 89) created buffers, and it will check the validity of ``memory`` and
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 90) ``format.type``. If those are invalid -1 is returned and errno is
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 91) set to ``EINVAL`` error code, otherwise :ref:`VIDIOC_CREATE_BUFS` returns
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 92) 0. It will never set errno to ``EBUSY`` error code in this particular
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 93) case.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 94) * - __u32
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 95) - ``memory``
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 96) - Applications set this field to ``V4L2_MEMORY_MMAP``,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 97) ``V4L2_MEMORY_DMABUF`` or ``V4L2_MEMORY_USERPTR``. See
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 98) :c:type:`v4l2_memory`
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 99) * - struct :c:type:`v4l2_format`
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 100) - ``format``
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 101) - Filled in by the application, preserved by the driver.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 102) * - __u32
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 103) - ``capabilities``
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 104) - Set by the driver. If 0, then the driver doesn't support
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 105) capabilities. In that case all you know is that the driver is
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 106) guaranteed to support ``V4L2_MEMORY_MMAP`` and *might* support
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 107) other :c:type:`v4l2_memory` types. It will not support any other
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 108) capabilities. See :ref:`here <v4l2-buf-capabilities>` for a list of the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 109) capabilities.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 110)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 111) If you want to just query the capabilities without making any
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 112) other changes, then set ``count`` to 0, ``memory`` to
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 113) ``V4L2_MEMORY_MMAP`` and ``format.type`` to the buffer type.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 114)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 115) * - __u32
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 116) - ``reserved``\ [7]
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 117) - A place holder for future extensions. Drivers and applications
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 118) must set the array to zero.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 119)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 120) Return Value
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 121) ============
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 122)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 123) On success 0 is returned, on error -1 and the ``errno`` variable is set
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 124) appropriately. The generic error codes are described at the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 125) :ref:`Generic Error Codes <gen-errors>` chapter.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 126)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 127) ENOMEM
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 128) No memory to allocate buffers for :ref:`memory mapped <mmap>` I/O.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 129)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 130) EINVAL
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 131) The buffer type (``format.type`` field), requested I/O method
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 132) (``memory``) or format (``format`` field) is not valid.
Orange Pi5 kernel
Deprecated Linux kernel 5.10.110 for OrangePi 5/5B/5+ boards
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