media/v4l/vidioc-reqbufs.rst

1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
13 VIDIOC_REQBUFS - Initiate Memory Mapping, User Pointer I/O or DMA buffer I/O
78 .. flat-table:: struct v4l2_requestbuffers
79     :header-rows:  0
80     :stub-columns: 0
83     * - __u32
84       - ``count``
85       - The number of buffers requested or granted.
86     * - __u32
87       - ``type``
88       - Type of the stream or buffers, this is the same as the struct
91     * - __u32
92       - ``memory``
93       - Applications set this field to ``V4L2_MEMORY_MMAP``,
96     * - __u32
97       - ``capabilities``
98       - Set by the driver. If 0, then the driver doesn't support
104 	If you want to query the capabilities with a minimum of side-effects,
109     * - __u8
110       - ``flags``
111       - Specifies additional buffer management attributes.
112 	See :ref:`memory-flags`.
113     * - __u8
114       - ``reserved``\ [3]
115       - Reserved for future extensions.
117 .. _v4l2-buf-capabilities:
118 .. _V4L2-BUF-CAP-SUPPORTS-MMAP:
119 .. _V4L2-BUF-CAP-SUPPORTS-USERPTR:
120 .. _V4L2-BUF-CAP-SUPPORTS-DMABUF:
121 .. _V4L2-BUF-CAP-SUPPORTS-REQUESTS:
122 .. _V4L2-BUF-CAP-SUPPORTS-ORPHANED-BUFS:
123 .. _V4L2-BUF-CAP-SUPPORTS-M2M-HOLD-CAPTURE-BUF:
124 .. _V4L2-BUF-CAP-SUPPORTS-MMAP-CACHE-HINTS:
125 .. _V4L2-BUF-CAP-SUPPORTS-MAX-NUM-BUFFERS:
126 .. _V4L2-BUF-CAP-SUPPORTS-REMOVE-BUFS:
128 .. flat-table:: V4L2 Buffer Capabilities Flags
129     :header-rows:  0
130     :stub-columns: 0
133     * - ``V4L2_BUF_CAP_SUPPORTS_MMAP``
134       - 0x00000001
135       - This buffer type supports the ``V4L2_MEMORY_MMAP`` streaming mode.
136     * - ``V4L2_BUF_CAP_SUPPORTS_USERPTR``
137       - 0x00000002
138       - This buffer type supports the ``V4L2_MEMORY_USERPTR`` streaming mode.
139     * - ``V4L2_BUF_CAP_SUPPORTS_DMABUF``
140       - 0x00000004
141       - This buffer type supports the ``V4L2_MEMORY_DMABUF`` streaming mode.
142     * - ``V4L2_BUF_CAP_SUPPORTS_REQUESTS``
143       - 0x00000008
144       - This buffer type supports :ref:`requests <media-request-api>`.
145     * - ``V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS``
146       - 0x00000010
147       - The kernel allows calling :ref:`VIDIOC_REQBUFS` while buffers are still
150     * - ``V4L2_BUF_CAP_SUPPORTS_M2M_HOLD_CAPTURE_BUF``
151       - 0x00000020
152       - Only valid for stateless decoders. If set, then userspace can set the
155     * - ``V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS``
156       - 0x00000040
157       - This capability is set by the driver to indicate that the queue supports
160         :ref:`V4L2_BUF_FLAG_NO_CACHE_INVALIDATE <V4L2-BUF-FLAG-NO-CACHE-INVALIDATE>`,
161         :ref:`V4L2_BUF_FLAG_NO_CACHE_CLEAN <V4L2-BUF-FLAG-NO-CACHE-CLEAN>` and
162         :ref:`V4L2_MEMORY_FLAG_NON_COHERENT <V4L2-MEMORY-FLAG-NON-COHERENT>`.
163     * - ``V4L2_BUF_CAP_SUPPORTS_MAX_NUM_BUFFERS``
164       - 0x00000080
165       - If set, then the ``max_num_buffers`` field in ``struct v4l2_create_buffers``
167     * - ``V4L2_BUF_CAP_SUPPORTS_REMOVE_BUFS``
168       - 0x00000100
169       - If set, then ``VIDIOC_REMOVE_BUFS`` is supported.
171 .. _memory-flags:
172 .. _V4L2-MEMORY-FLAG-NON-COHERENT:
174 .. flat-table:: Memory Consistency Flags
175     :header-rows:  0
176     :stub-columns: 0
179     * - ``V4L2_MEMORY_FLAG_NON_COHERENT``
180       - 0x00000001
181       - A buffer is allocated either in coherent (it will be automatically
182 	coherent between the CPU and the bus) or non-coherent memory. The
186 	buffer. However, this requires extra care from the driver -- it must
189 	allocate the buffer in non-coherent memory. The flag takes effect
192 	<V4L2-BUF-CAP-SUPPORTS-MMAP-CACHE-HINTS>` capability.
201 On success 0 is returned, on error -1 and the ``errno`` variable is set
203 :ref:`Generic Error Codes <gen-errors>` chapter.