3.2.18. ioctl DMX_EXPBUF¶
3.2.18.1. Name¶
DMX_EXPBUF - Export a buffer as a DMABUF file descriptor.
Warning
this API is still experimental
3.2.18.2. Synopsis¶
- 
DMX_EXPBUF¶
int ioctl(int fd, DMX_EXPBUF, struct dmx_exportbuffer *argp)
3.2.18.3. Arguments¶
- fd
- File descriptor returned by - open().
- argp
- Pointer to struct - dmx_exportbuffer.
3.2.18.4. Description¶
This ioctl is an extension to the memory mapping I/O method. It can be used to export a buffer as a DMABUF file at any time after buffers have been allocated with the ioctl DMX_REQBUFS ioctl.
To export a buffer, applications fill struct dmx_exportbuffer.
Applications must set the index field. Valid index numbers
range from zero to the number of buffers allocated with ioctl DMX_REQBUFS
(struct dmx_requestbuffers count) minus one.
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 ioctl DMX_EXPBUF calls.
After calling ioctl DMX_EXPBUF the fd field will be set by a
driver, on success. This is a DMABUF file descriptor. The application may
pass it to other DMABUF-aware devices. It is recommended to close a DMABUF
file when it is no longer used to allow the associated memory to be reclaimed.
3.2.18.5. Examples¶
int buffer_export(int v4lfd, enum dmx_buf_type bt, int index, int *dmafd)
{
    struct dmx_exportbuffer expbuf;
    memset(&expbuf, 0, sizeof(expbuf));
    expbuf.type = bt;
    expbuf.index = index;
    if (ioctl(v4lfd, DMX_EXPBUF, &expbuf) == -1) {
        perror("DMX_EXPBUF");
        return -1;
    }
    *dmafd = expbuf.fd;
    return 0;
}
3.2.18.6. 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
Generic Error Codes chapter.
- EINVAL
- A queue is not in MMAP mode or DMABUF exporting is not supported or - flagsor- indexfields are invalid.