64 lines
1.6 KiB
ReStructuredText
Executable file
64 lines
1.6 KiB
ReStructuredText
Executable file
.. _DMX_QUERYBUF:
|
|
|
|
******************
|
|
ioctl DMX_QUERYBUF
|
|
******************
|
|
|
|
Name
|
|
====
|
|
|
|
DMX_QUERYBUF - Query the status of a buffer
|
|
|
|
.. warning:: this API is still experimental
|
|
|
|
|
|
Synopsis
|
|
========
|
|
|
|
.. c:function:: int ioctl( int fd, DMX_QUERYBUF, struct dvb_buffer *argp )
|
|
:name: DMX_QUERYBUF
|
|
|
|
|
|
Arguments
|
|
=========
|
|
|
|
``fd``
|
|
File descriptor returned by :ref:`open() <dmx_fopen>`.
|
|
|
|
``argp``
|
|
Pointer to struct :c:type:`dvb_buffer`.
|
|
|
|
|
|
Description
|
|
===========
|
|
|
|
This ioctl is part of the mmap streaming I/O method. It can
|
|
be used to query the status of a buffer at any time after buffers have
|
|
been allocated with the :ref:`DMX_REQBUFS` ioctl.
|
|
|
|
Applications set the ``index`` field. Valid index numbers range from zero
|
|
to the number of buffers allocated with :ref:`DMX_REQBUFS`
|
|
(struct :c:type:`dvb_requestbuffers` ``count``) minus one.
|
|
|
|
After calling :ref:`DMX_QUERYBUF` with a pointer to this structure,
|
|
drivers return an error code or fill the rest of the structure.
|
|
|
|
On success, the ``offset`` will contain the offset of the buffer from the
|
|
start of the device memory, the ``length`` field its size, and the
|
|
``bytesused`` the number of bytes occupied by data in the buffer (payload).
|
|
|
|
Return Value
|
|
============
|
|
|
|
On success 0 is returned, the ``offset`` will contain the offset of the
|
|
buffer from the start of the device memory, the ``length`` field its size,
|
|
and the ``bytesused`` the number of bytes occupied by data in the buffer
|
|
(payload).
|
|
|
|
On error it returns -1 and the ``errno`` variable is set
|
|
appropriately. The generic error codes are described at the
|
|
:ref:`Generic Error Codes <gen-errors>` chapter.
|
|
|
|
EINVAL
|
|
The ``index`` is out of bounds.
|