1 .. SPDX-License-Identifier: GFDL-1.1-no-invari 1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2 .. c:namespace:: DTV.dmx 2 .. c:namespace:: DTV.dmx
3 3
4 .. _DMX_QUERYBUF: 4 .. _DMX_QUERYBUF:
5 5
6 ****************** 6 ******************
7 ioctl DMX_QUERYBUF 7 ioctl DMX_QUERYBUF
8 ****************** 8 ******************
9 9
10 Name 10 Name
11 ==== 11 ====
12 12
13 DMX_QUERYBUF - Query the status of a buffer 13 DMX_QUERYBUF - Query the status of a buffer
14 14
15 .. warning:: this API is still experimental 15 .. warning:: this API is still experimental
16 16
17 Synopsis 17 Synopsis
18 ======== 18 ========
19 19
20 .. c:macro:: DMX_QUERYBUF 20 .. c:macro:: DMX_QUERYBUF
21 21
22 ``int ioctl(int fd, DMX_QUERYBUF, struct dvb_b 22 ``int ioctl(int fd, DMX_QUERYBUF, struct dvb_buffer *argp)``
23 23
24 Arguments 24 Arguments
25 ========= 25 =========
26 26
27 ``fd`` 27 ``fd``
28 File descriptor returned by :c:func:`open( 28 File descriptor returned by :c:func:`open()`.
29 29
30 ``argp`` 30 ``argp``
31 Pointer to struct :c:type:`dvb_buffer`. 31 Pointer to struct :c:type:`dvb_buffer`.
32 32
33 Description 33 Description
34 =========== 34 ===========
35 35
36 This ioctl is part of the mmap streaming I/O m 36 This ioctl is part of the mmap streaming I/O method. It can
37 be used to query the status of a buffer at any 37 be used to query the status of a buffer at any time after buffers have
38 been allocated with the :ref:`DMX_REQBUFS` ioc 38 been allocated with the :ref:`DMX_REQBUFS` ioctl.
39 39
40 Applications set the ``index`` field. Valid in 40 Applications set the ``index`` field. Valid index numbers range from zero
41 to the number of buffers allocated with :ref:` 41 to the number of buffers allocated with :ref:`DMX_REQBUFS`
42 (struct :c:type:`dvb_requestbuffers` ``count`` 42 (struct :c:type:`dvb_requestbuffers` ``count``) minus one.
43 43
44 After calling :ref:`DMX_QUERYBUF` with a point 44 After calling :ref:`DMX_QUERYBUF` with a pointer to this structure,
45 drivers return an error code or fill the rest 45 drivers return an error code or fill the rest of the structure.
46 46
47 On success, the ``offset`` will contain the of 47 On success, the ``offset`` will contain the offset of the buffer from the
48 start of the device memory, the ``length`` fie 48 start of the device memory, the ``length`` field its size, and the
49 ``bytesused`` the number of bytes occupied by 49 ``bytesused`` the number of bytes occupied by data in the buffer (payload).
50 50
51 Return Value 51 Return Value
52 ============ 52 ============
53 53
54 On success 0 is returned, the ``offset`` will 54 On success 0 is returned, the ``offset`` will contain the offset of the
55 buffer from the start of the device memory, th 55 buffer from the start of the device memory, the ``length`` field its size,
56 and the ``bytesused`` the number of bytes occu 56 and the ``bytesused`` the number of bytes occupied by data in the buffer
57 (payload). 57 (payload).
58 58
59 On error it returns -1 and the ``errno`` varia 59 On error it returns -1 and the ``errno`` variable is set
60 appropriately. The generic error codes are des 60 appropriately. The generic error codes are described at the
61 :ref:`Generic Error Codes <gen-errors>` chapte 61 :ref:`Generic Error Codes <gen-errors>` chapter.
62 62
63 EINVAL 63 EINVAL
64 The ``index`` is out of bounds. 64 The ``index`` is out of bounds.
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