1 .. SPDX-License-Identifier: GFDL-1.1-no-invari
2 .. c:namespace:: DTV.dmx
3
4 .. _DMX_REQBUFS:
5
6 *****************
7 ioctl DMX_REQBUFS
8 *****************
9
10 Name
11 ====
12
13 DMX_REQBUFS - Initiate Memory Mapping and/or D
14
15 .. warning:: this API is still experimental
16
17 Synopsis
18 ========
19
20 .. c:macro:: DMX_REQBUFS
21
22 ``int ioctl(int fd, DMX_REQBUFS, struct dmx_re
23
24 Arguments
25 =========
26
27 ``fd``
28 File descriptor returned by :c:func:`open(
29
30 ``argp``
31 Pointer to struct :c:type:`dmx_requestbuff
32
33 Description
34 ===========
35
36 This ioctl is used to initiate a memory mapped
37
38 Memory mapped buffers are located in device me
39 with this ioctl before they can be mapped into
40 space. User buffers are allocated by applicati
41 ioctl is merely used to switch the driver into
42 to setup some internal structures. Similarly,
43 allocated by applications through a device dri
44 configures the driver into DMABUF I/O mode wit
45 allocation.
46
47 To allocate device buffers applications initia
48 struct :c:type:`dmx_requestbuffers` structure.
49 to the desired number of buffers, and ``size`
50 buffer.
51
52 When the ioctl is called with a pointer to thi
53 attempt to allocate the requested number of bu
54 number allocated in the ``count`` field. The `
55 number is also possible when the driver requir
56 function correctly. The actual allocated buffe
57 at ``size``, and can be smaller than what's re
58
59 When this I/O method is not supported, the ioc
60 error code.
61
62 Applications can call :ref:`DMX_REQBUFS` again
63 buffers, however this cannot succeed when any
64 A ``count`` value of zero frees all buffers, a
65 any DMA in progress.
66
67 Return Value
68 ============
69
70 On success 0 is returned, on error -1 and the
71 appropriately. The generic error codes are des
72 :ref:`Generic Error Codes <gen-errors>` chapte
73
74 EOPNOTSUPP
75 The the requested I/O method is not suppo
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.