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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 10:05:51 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 10:05:51 +0000 |
commit | 5d1646d90e1f2cceb9f0828f4b28318cd0ec7744 (patch) | |
tree | a94efe259b9009378be6d90eb30d2b019d95c194 /Documentation/userspace-api/media/dvb/dmx-expbuf.rst | |
parent | Initial commit. (diff) | |
download | linux-upstream/5.10.209.tar.xz linux-upstream/5.10.209.zip |
Adding upstream version 5.10.209.upstream/5.10.209upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | Documentation/userspace-api/media/dvb/dmx-expbuf.rst | 87 |
1 files changed, 87 insertions, 0 deletions
diff --git a/Documentation/userspace-api/media/dvb/dmx-expbuf.rst b/Documentation/userspace-api/media/dvb/dmx-expbuf.rst new file mode 100644 index 000000000..5cdc2035e --- /dev/null +++ b/Documentation/userspace-api/media/dvb/dmx-expbuf.rst @@ -0,0 +1,87 @@ +.. 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. |