65 lines
1.7 KiB
ReStructuredText
65 lines
1.7 KiB
ReStructuredText
|
.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
|
||
|
|
.. c:namespace:: DTV.dmx
|
||
|
|
|
||
|
|
.. _DMX_QUERYBUF:
|
||
|
|
|
||
|
|
******************
|
||
|
|
ioctl DMX_QUERYBUF
|
||
|
|
******************
|
||
|
|
|
||
|
|
Name
|
||
|
|
====
|
||
|
|
|
||
|
|
DMX_QUERYBUF - Query the status of a buffer
|
||
|
|
|
||
|
|
.. warning:: this API is still experimental
|
||
|
|
|
||
|
|
Synopsis
|
||
|
|
========
|
||
|
|
|
||
|
|
.. c:macro:: DMX_QUERYBUF
|
||
|
|
|
||
|
|
``int ioctl(int fd, DMX_QUERYBUF, struct dvb_buffer *argp)``
|
||
|
|
|
||
|
|
Arguments
|
||
|
|
=========
|
||
|
|
|
||
|
|
``fd``
|
||
|
|
File descriptor returned by :c:func:`open()`.
|
||
|
|
|
||
|
|
``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.
|