Based on kernel version 6.8. Page generated on 2024-03-11 21:26 EST.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 |
.. 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.
|
