ioctl VIDIOC_EXPBUF &manvol; VIDIOC_EXPBUF Export a buffer as a DMABUF file descriptor. int ioctl int fd int request struct v4l2_exportbuffer *argp fd &fd; request VIDIOC_EXPBUF argp This is an experimental interface and may change in the future. This ioctl is an extension to the memory mapping I/O method, therefore it is available only for V4L2_MEMORY_MMAP buffers. It can be used to export a buffer as a DMABUF file at any time after buffers have been allocated with the &VIDIOC-REQBUFS; ioctl. To export a buffer, applications fill &v4l2-exportbuffer;. The type field is set to the same buffer type as was previously used with &v4l2-requestbuffers; type . Applications must also set the index field. Valid index numbers range from zero to the number of buffers allocated with &VIDIOC-REQBUFS; (&v4l2-requestbuffers; count ) minus one. For the multi-planar API, applications set the plane field to the index of the plane to be exported. Valid planes range from zero to the maximal number of valid planes for the currently active format. For the single-planar API, applications must set plane to zero. Additional flags may be posted in the flags field. Refer to a manual for open() for details. Currently only O_CLOEXEC, O_RDONLY, O_WRONLY, and O_RDWR are supported. All other fields must be set to zero. In the case of multi-planar API, every plane is exported separately using multiple VIDIOC_EXPBUF calls. After calling VIDIOC_EXPBUF the fd field will be set by a driver. This is a DMABUF file descriptor. The application may pass it to other DMABUF-aware devices. Refer to DMABUF importing for details about importing DMABUF files into V4L2 nodes. It is recommended to close a DMABUF file when it is no longer used to allow the associated memory to be reclaimed. int buffer_export(int v4lfd, &v4l2-buf-type; bt, int index, int *dmafd) { &v4l2-exportbuffer; expbuf; memset(&expbuf, 0, sizeof(expbuf)); expbuf.type = bt; expbuf.index = index; if (ioctl(v4lfd, &VIDIOC-EXPBUF;, &expbuf) == -1) { perror("VIDIOC_EXPBUF"); return -1; } *dmafd = expbuf.fd; return 0; } int buffer_export_mp(int v4lfd, &v4l2-buf-type; bt, int index, int dmafd[], int n_planes) { int i; for (i = 0; i < n_planes; ++i) { &v4l2-exportbuffer; expbuf; memset(&expbuf, 0, sizeof(expbuf)); expbuf.type = bt; expbuf.index = index; expbuf.plane = i; if (ioctl(v4lfd, &VIDIOC-EXPBUF;, &expbuf) == -1) { perror("VIDIOC_EXPBUF"); while (i) close(dmafd[--i]); return -1; } dmafd[i] = expbuf.fd; } return 0; } &cs-str; __u32 type Type of the buffer, same as &v4l2-format; type or &v4l2-requestbuffers; type, set by the application. See __u32 index Number of the buffer, set by the application. This field is only used for memory mapping I/O and can range from zero to the number of buffers allocated with the &VIDIOC-REQBUFS; and/or &VIDIOC-CREATE-BUFS; ioctls. __u32 plane Index of the plane to be exported when using the multi-planar API. Otherwise this value must be set to zero. __u32 flags Flags for the newly created file, currently only O_CLOEXEC , O_RDONLY, O_WRONLY , and O_RDWR are supported, refer to the manual of open() for more details. __s32 fd The DMABUF file descriptor associated with a buffer. Set by the driver. __u32 reserved[11] Reserved field for future use. Must be set to zero. &return-value; EINVAL A queue is not in MMAP mode or DMABUF exporting is not supported or flags or type or index or plane fields are invalid.