.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later .. c:namespace:: DTV.dmx

.. _DMX_EXPBUF:

ioctl DMX_EXPBUF

Name

DMX_EXPBUF - Export a buffer as a DMABUF file descriptor.

.. warning:: this API is still experimental

Synopsis

.. c:macro:: DMX_EXPBUF

int ioctl(int fd, DMX_EXPBUF, struct dmx_exportbuffer *argp)

Arguments

fd File descriptor returned by :c:func:open().

argp Pointer to struct :c:type:dmx_exportbuffer.

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 :ref:DMX_REQBUFS ioctl.

To export a buffer, applications fill struct :c:type:dmx_exportbuffer. Applications must set the index field. Valid index numbers range from zero to the number of buffers allocated with :ref:DMX_REQBUFS (struct :c:type: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 :ref:DMX_EXPBUF calls.

After calling :ref: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.

Examples

.. code-block:: c

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;
}

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 :ref:Generic Error Codes <gen-errors> chapter.

EINVAL A queue is not in MMAP mode or DMABUF exporting is not supported or flags or index fields are invalid.