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author | Jens Axboe <axboe@kernel.dk> | 2018-02-07 15:54:20 -0700 |
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committer | Jens Axboe <axboe@kernel.dk> | 2018-02-07 15:54:20 -0700 |
commit | 61a695184fcc8f225327206b88320279dd8684af (patch) | |
tree | 6cbda2b0e7de94ebad95072d17cc0aa82c9d8ab3 /Documentation/media/uapi/dvb/dmx-expbuf.rst | |
parent | 9e05c864993c5442227f83ae1694a737d7a102ed (diff) | |
parent | 581e400ff935d34d95811258586128bf11baef15 (diff) |
Merge branch 'master' into test
* master: (1190 commits)
ASoC: stm32: add of dependency for stm32 drivers
ASoC: mt8173-rt5650: fix child-node lookup
ASoC: dapm: fix debugfs read using path->connected
platform/x86: samsung-laptop: Re-use DEFINE_SHOW_ATTRIBUTE() macro
platform/x86: ideapad-laptop: Re-use DEFINE_SHOW_ATTRIBUTE() macro
platform/x86: dell-laptop: Re-use DEFINE_SHOW_ATTRIBUTE() macro
seq_file: Introduce DEFINE_SHOW_ATTRIBUTE() helper macro
Documentation/sysctl/user.txt: fix typo
MAINTAINERS: update ARM/QUALCOMM SUPPORT patterns
MAINTAINERS: update various PALM patterns
MAINTAINERS: update "ARM/OXNAS platform support" patterns
MAINTAINERS: update Cortina/Gemini patterns
MAINTAINERS: remove ARM/CLKDEV SUPPORT file pattern
MAINTAINERS: remove ANDROID ION pattern
mm: docs: add blank lines to silence sphinx "Unexpected indentation" errors
mm: docs: fix parameter names mismatch
mm: docs: fixup punctuation
pipe: read buffer limits atomically
pipe: simplify round_pipe_size()
pipe: reject F_SETPIPE_SZ with size over UINT_MAX
...
Diffstat (limited to 'Documentation/media/uapi/dvb/dmx-expbuf.rst')
-rw-r--r-- | Documentation/media/uapi/dvb/dmx-expbuf.rst | 88 |
1 files changed, 88 insertions, 0 deletions
diff --git a/Documentation/media/uapi/dvb/dmx-expbuf.rst b/Documentation/media/uapi/dvb/dmx-expbuf.rst new file mode 100644 index 000000000000..2d96cfe891df --- /dev/null +++ b/Documentation/media/uapi/dvb/dmx-expbuf.rst @@ -0,0 +1,88 @@ +.. _DMX_EXPBUF: + +**************** +ioctl DMX_EXPBUF +**************** + +Name +==== + +DMX_EXPBUF - Export a buffer as a DMABUF file descriptor. + +.. warning:: this API is still experimental + + +Synopsis +======== + +.. c:function:: int ioctl( int fd, DMX_EXPBUF, struct dmx_exportbuffer *argp ) + :name: DMX_EXPBUF + + +Arguments +========= + +``fd`` + File descriptor returned by :ref:`open() <dmx_fopen>`. + +``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. |