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1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later2.. c:namespace:: DTV.dmx3 4.. _DMX_EXPBUF:5 6****************7ioctl DMX_EXPBUF8****************9 10Name11====12 13DMX_EXPBUF - Export a buffer as a DMABUF file descriptor.14 15.. warning:: this API is still experimental16 17Synopsis18========19 20.. c:macro:: DMX_EXPBUF21 22``int ioctl(int fd, DMX_EXPBUF, struct dmx_exportbuffer *argp)``23 24Arguments25=========26 27``fd``28 File descriptor returned by :c:func:`open()`.29 30``argp``31 Pointer to struct :c:type:`dmx_exportbuffer`.32 33Description34===========35 36This ioctl is an extension to the memory mapping I/O method.37It can be used to export a buffer as a DMABUF file at any time after38buffers have been allocated with the :ref:`DMX_REQBUFS` ioctl.39 40To export a buffer, applications fill struct :c:type:`dmx_exportbuffer`.41Applications must set the ``index`` field. Valid index numbers42range from zero to the number of buffers allocated with :ref:`DMX_REQBUFS`43(struct :c:type:`dmx_requestbuffers` ``count``) minus one.44Additional flags may be posted in the ``flags`` field. Refer to a manual45for open() for details. Currently only O_CLOEXEC, O_RDONLY, O_WRONLY,46and O_RDWR are supported.47All other fields must be set to zero. In the48case of multi-planar API, every plane is exported separately using49multiple :ref:`DMX_EXPBUF` calls.50 51After calling :ref:`DMX_EXPBUF` the ``fd`` field will be set by a52driver, on success. This is a DMABUF file descriptor. The application may53pass it to other DMABUF-aware devices. It is recommended to close a DMABUF54file when it is no longer used to allow the associated memory to be reclaimed.55 56Examples57========58 59.. code-block:: c60 61 int buffer_export(int v4lfd, enum dmx_buf_type bt, int index, int *dmafd)62 {63 struct dmx_exportbuffer expbuf;64 65 memset(&expbuf, 0, sizeof(expbuf));66 expbuf.type = bt;67 expbuf.index = index;68 if (ioctl(v4lfd, DMX_EXPBUF, &expbuf) == -1) {69 perror("DMX_EXPBUF");70 return -1;71 }72 73 *dmafd = expbuf.fd;74 75 return 0;76 }77 78Return Value79============80 81On success 0 is returned, on error -1 and the ``errno`` variable is set82appropriately. The generic error codes are described at the83:ref:`Generic Error Codes <gen-errors>` chapter.84 85EINVAL86 A queue is not in MMAP mode or DMABUF exporting is not supported or87 ``flags`` or ``index`` fields are invalid.88