a114a585be
The "reserved" field was a way, used at V4L2 API, to add new data to existing structs without breaking userspace. However, there are now clever ways of doing that, without needing to add an uneeded overhead. So, get rid of them. Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
89 lines
2.2 KiB
ReStructuredText
89 lines
2.2 KiB
ReStructuredText
.. _DMX_EXPBUF:
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****************
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ioctl DMX_EXPBUF
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****************
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Name
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====
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DMX_EXPBUF - Export a buffer as a DMABUF file descriptor.
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.. warning:: this API is still experimental
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Synopsis
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========
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.. c:function:: int ioctl( int fd, DMX_EXPBUF, struct dmx_exportbuffer *argp )
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:name: DMX_EXPBUF
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Arguments
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=========
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``fd``
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File descriptor returned by :ref:`open() <dmx_fopen>`.
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``argp``
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Pointer to struct :c:type:`dmx_exportbuffer`.
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Description
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===========
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This ioctl is an extension to the memory mapping I/O method.
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It can be used to export a buffer as a DMABUF file at any time after
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buffers have been allocated with the :ref:`DMX_REQBUFS` ioctl.
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To export a buffer, applications fill struct :c:type:`dmx_exportbuffer`.
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Applications must set the ``index`` field. Valid index numbers
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range from zero to the number of buffers allocated with :ref:`DMX_REQBUFS`
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(struct :c:type:`dmx_requestbuffers` ``count``) minus one.
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Additional flags may be posted in the ``flags`` field. Refer to a manual
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for open() for details. Currently only O_CLOEXEC, O_RDONLY, O_WRONLY,
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and O_RDWR are supported.
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All other fields must be set to zero. In the
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case of multi-planar API, every plane is exported separately using
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multiple :ref:`DMX_EXPBUF` calls.
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After calling :ref:`DMX_EXPBUF` the ``fd`` field will be set by a
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driver, on success. This is a DMABUF file descriptor. The application may
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pass it to other DMABUF-aware devices. It is recommended to close a DMABUF
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file when it is no longer used to allow the associated memory to be reclaimed.
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Examples
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========
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.. code-block:: c
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int buffer_export(int v4lfd, enum dmx_buf_type bt, int index, int *dmafd)
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{
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struct dmx_exportbuffer expbuf;
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memset(&expbuf, 0, sizeof(expbuf));
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expbuf.type = bt;
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expbuf.index = index;
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if (ioctl(v4lfd, DMX_EXPBUF, &expbuf) == -1) {
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perror("DMX_EXPBUF");
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return -1;
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}
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*dmafd = expbuf.fd;
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return 0;
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}
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Return Value
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============
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On success 0 is returned, on error -1 and the ``errno`` variable is set
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appropriately. The generic error codes are described at the
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:ref:`Generic Error Codes <gen-errors>` chapter.
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EINVAL
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A queue is not in MMAP mode or DMABUF exporting is not supported or
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``flags`` or ``index`` fields are invalid.
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