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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>
64 lines
1.6 KiB
ReStructuredText
64 lines
1.6 KiB
ReStructuredText
.. _DMX_QUERYBUF:
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******************
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ioctl DMX_QUERYBUF
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******************
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Name
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====
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DMX_QUERYBUF - Query the status of a buffer
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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_QUERYBUF, struct dvb_buffer *argp )
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:name: DMX_QUERYBUF
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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:`dvb_buffer`.
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Description
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===========
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This ioctl is part of the mmap streaming I/O method. It can
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be used to query the status of a buffer at any time after buffers have
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been allocated with the :ref:`DMX_REQBUFS` ioctl.
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Applications set the ``index`` field. Valid index numbers range from zero
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to the number of buffers allocated with :ref:`DMX_REQBUFS`
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(struct :c:type:`dvb_requestbuffers` ``count``) minus one.
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After calling :ref:`DMX_QUERYBUF` with a pointer to this structure,
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drivers return an error code or fill the rest of the structure.
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On success, the ``offset`` will contain the offset of the buffer from the
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start of the device memory, the ``length`` field its size, and the
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``bytesused`` the number of bytes occupied by data in the buffer (payload).
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Return Value
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============
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On success 0 is returned, the ``offset`` will contain the offset of the
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buffer from the start of the device memory, the ``length`` field its size,
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and the ``bytesused`` the number of bytes occupied by data in the buffer
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(payload).
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On error it returns -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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The ``index`` is out of bounds.
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