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1 | .. -*- coding: utf-8; mode: rst -*- |
2 | ||
af4a4d0d | 3 | .. _VIDIOC_EXPBUF: |
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4 | |
5 | ******************* | |
6 | ioctl VIDIOC_EXPBUF | |
7 | ******************* | |
8 | ||
9 | *man VIDIOC_EXPBUF(2)* | |
10 | ||
11 | Export a buffer as a DMABUF file descriptor. | |
12 | ||
13 | ||
14 | Synopsis | |
15 | ======== | |
16 | ||
b7e67f6c | 17 | .. cpp:function:: int ioctl( int fd, int request, struct v4l2_exportbuffer *argp ) |
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18 | |
19 | Arguments | |
20 | ========= | |
21 | ||
22 | ``fd`` | |
23 | File descriptor returned by :ref:`open() <func-open>`. | |
24 | ||
25 | ``request`` | |
26 | VIDIOC_EXPBUF | |
27 | ||
28 | ``argp`` | |
29 | ||
30 | ||
31 | Description | |
32 | =========== | |
33 | ||
34 | This ioctl is an extension to the :ref:`memory mapping <mmap>` I/O | |
35 | method, therefore it is available only for ``V4L2_MEMORY_MMAP`` buffers. | |
36 | It can be used to export a buffer as a DMABUF file at any time after | |
37 | buffers have been allocated with the | |
7347081e | 38 | :ref:`VIDIOC_REQBUFS` ioctl. |
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39 | |
40 | To export a buffer, applications fill struct | |
41 | :ref:`v4l2_exportbuffer <v4l2-exportbuffer>`. The ``type`` field is | |
42 | set to the same buffer type as was previously used with struct | |
43 | :ref:`v4l2_requestbuffers <v4l2-requestbuffers>` ``type``. | |
44 | Applications must also set the ``index`` field. Valid index numbers | |
45 | range from zero to the number of buffers allocated with | |
7347081e | 46 | :ref:`VIDIOC_REQBUFS` (struct |
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47 | :ref:`v4l2_requestbuffers <v4l2-requestbuffers>` ``count``) minus |
48 | one. For the multi-planar API, applications set the ``plane`` field to | |
49 | the index of the plane to be exported. Valid planes range from zero to | |
50 | the maximal number of valid planes for the currently active format. For | |
51 | the single-planar API, applications must set ``plane`` to zero. | |
52 | Additional flags may be posted in the ``flags`` field. Refer to a manual | |
53 | for open() for details. Currently only O_CLOEXEC, O_RDONLY, O_WRONLY, | |
54 | and O_RDWR are supported. All other fields must be set to zero. In the | |
55 | case of multi-planar API, every plane is exported separately using | |
2212ff25 | 56 | multiple :ref:`VIDIOC_EXPBUF` calls. |
5377d91f | 57 | |
2212ff25 | 58 | After calling :ref:`VIDIOC_EXPBUF` the ``fd`` field will be set by a |
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59 | driver. This is a DMABUF file descriptor. The application may pass it to |
60 | other DMABUF-aware devices. Refer to :ref:`DMABUF importing <dmabuf>` | |
61 | for details about importing DMABUF files into V4L2 nodes. It is | |
62 | recommended to close a DMABUF file when it is no longer used to allow | |
63 | the associated memory to be reclaimed. | |
64 | ||
65 | ||
66 | Examples | |
67 | ======== | |
68 | ||
69 | ||
70 | .. code-block:: c | |
71 | ||
72 | int buffer_export(int v4lfd, enum v4l2_buf_type bt, int index, int *dmafd) | |
73 | { | |
74 | struct v4l2_exportbuffer expbuf; | |
75 | ||
76 | memset(&expbuf, 0, sizeof(expbuf)); | |
77 | expbuf.type = bt; | |
78 | expbuf.index = index; | |
79 | if (ioctl(v4lfd, VIDIOC_EXPBUF, &expbuf) == -1) { | |
80 | perror("VIDIOC_EXPBUF"); | |
81 | return -1; | |
82 | } | |
83 | ||
84 | *dmafd = expbuf.fd; | |
85 | ||
86 | return 0; | |
87 | } | |
88 | ||
89 | ||
90 | .. code-block:: c | |
91 | ||
92 | int buffer_export_mp(int v4lfd, enum v4l2_buf_type bt, int index, | |
93 | int dmafd[], int n_planes) | |
94 | { | |
95 | int i; | |
96 | ||
97 | for (i = 0; i < n_planes; ++i) { | |
98 | struct v4l2_exportbuffer expbuf; | |
99 | ||
100 | memset(&expbuf, 0, sizeof(expbuf)); | |
101 | expbuf.type = bt; | |
102 | expbuf.index = index; | |
103 | expbuf.plane = i; | |
104 | if (ioctl(v4lfd, VIDIOC_EXPBUF, &expbuf) == -1) { | |
105 | perror("VIDIOC_EXPBUF"); | |
106 | while (i) | |
107 | close(dmafd[--i]); | |
108 | return -1; | |
109 | } | |
110 | dmafd[i] = expbuf.fd; | |
111 | } | |
112 | ||
113 | return 0; | |
114 | } | |
115 | ||
116 | ||
117 | .. _v4l2-exportbuffer: | |
118 | ||
119 | .. flat-table:: struct v4l2_exportbuffer | |
120 | :header-rows: 0 | |
121 | :stub-columns: 0 | |
122 | :widths: 1 1 2 | |
123 | ||
124 | ||
125 | - .. row 1 | |
126 | ||
127 | - __u32 | |
128 | ||
129 | - ``type`` | |
130 | ||
131 | - Type of the buffer, same as struct | |
132 | :ref:`v4l2_format <v4l2-format>` ``type`` or struct | |
133 | :ref:`v4l2_requestbuffers <v4l2-requestbuffers>` ``type``, set | |
134 | by the application. See :ref:`v4l2-buf-type` | |
135 | ||
136 | - .. row 2 | |
137 | ||
138 | - __u32 | |
139 | ||
140 | - ``index`` | |
141 | ||
142 | - Number of the buffer, set by the application. This field is only | |
143 | used for :ref:`memory mapping <mmap>` I/O and can range from | |
144 | zero to the number of buffers allocated with the | |
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145 | :ref:`VIDIOC_REQBUFS` and/or |
146 | :ref:`VIDIOC_CREATE_BUFS` ioctls. | |
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147 | |
148 | - .. row 3 | |
149 | ||
150 | - __u32 | |
151 | ||
152 | - ``plane`` | |
153 | ||
154 | - Index of the plane to be exported when using the multi-planar API. | |
155 | Otherwise this value must be set to zero. | |
156 | ||
157 | - .. row 4 | |
158 | ||
159 | - __u32 | |
160 | ||
161 | - ``flags`` | |
162 | ||
163 | - Flags for the newly created file, currently only ``O_CLOEXEC``, | |
164 | ``O_RDONLY``, ``O_WRONLY``, and ``O_RDWR`` are supported, refer to | |
165 | the manual of open() for more details. | |
166 | ||
167 | - .. row 5 | |
168 | ||
169 | - __s32 | |
170 | ||
171 | - ``fd`` | |
172 | ||
173 | - The DMABUF file descriptor associated with a buffer. Set by the | |
174 | driver. | |
175 | ||
176 | - .. row 6 | |
177 | ||
178 | - __u32 | |
179 | ||
180 | - ``reserved[11]`` | |
181 | ||
182 | - Reserved field for future use. Drivers and applications must set | |
183 | the array to zero. | |
184 | ||
185 | ||
186 | ||
187 | Return Value | |
188 | ============ | |
189 | ||
190 | On success 0 is returned, on error -1 and the ``errno`` variable is set | |
191 | appropriately. The generic error codes are described at the | |
192 | :ref:`Generic Error Codes <gen-errors>` chapter. | |
193 | ||
194 | EINVAL | |
195 | A queue is not in MMAP mode or DMABUF exporting is not supported or | |
196 | ``flags`` or ``type`` or ``index`` or ``plane`` fields are invalid. |