1.. This file is dual-licensed: you can use it either under the terms
2.. of the GPL 2.0 or the GFDL 1.1+ license, at your option. Note that this
3.. dual licensing only applies to this file, and not this project as a
4.. whole.
5..
6.. a) This file is free software; you can redistribute it and/or
7..    modify it under the terms of the GNU General Public License as
8..    published by the Free Software Foundation version 2 of
9..    the License.
10..
11..    This file is distributed in the hope that it will be useful,
12..    but WITHOUT ANY WARRANTY; without even the implied warranty of
13..    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14..    GNU General Public License for more details.
15..
16.. Or, alternatively,
17..
18.. b) Permission is granted to copy, distribute and/or modify this
19..    document under the terms of the GNU Free Documentation License,
20..    Version 1.1 or any later version published by the Free Software
21..    Foundation, with no Invariant Sections, no Front-Cover Texts
22..    and no Back-Cover Texts. A copy of the license is included at
23..    Documentation/userspace-api/media/fdl-appendix.rst.
24..
25.. TODO: replace it to GPL-2.0 OR GFDL-1.1-or-later WITH no-invariant-sections
26
27.. _media_request_ioc_queue:
28
29*****************************
30ioctl MEDIA_REQUEST_IOC_QUEUE
31*****************************
32
33Name
34====
35
36MEDIA_REQUEST_IOC_QUEUE - Queue a request
37
38
39Synopsis
40========
41
42.. c:function:: int ioctl( int request_fd, MEDIA_REQUEST_IOC_QUEUE )
43    :name: MEDIA_REQUEST_IOC_QUEUE
44
45
46Arguments
47=========
48
49``request_fd``
50    File descriptor returned by :ref:`MEDIA_IOC_REQUEST_ALLOC`.
51
52
53Description
54===========
55
56If the media device supports :ref:`requests <media-request-api>`, then
57this request ioctl can be used to queue a previously allocated request.
58
59If the request was successfully queued, then the file descriptor can be
60:ref:`polled <request-func-poll>` to wait for the request to complete.
61
62If the request was already queued before, then ``EBUSY`` is returned.
63Other errors can be returned if the contents of the request contained
64invalid or inconsistent data, see the next section for a list of
65common error codes. On error both the request and driver state are unchanged.
66
67Once a request is queued, then the driver is required to gracefully handle
68errors that occur when the request is applied to the hardware. The
69exception is the ``EIO`` error which signals a fatal error that requires
70the application to stop streaming to reset the hardware state.
71
72It is not allowed to mix queuing requests with queuing buffers directly
73(without a request). ``EBUSY`` will be returned if the first buffer was
74queued directly and you next try to queue a request, or vice versa.
75
76A request must contain at least one buffer, otherwise this ioctl will
77return an ``ENOENT`` error.
78
79Return Value
80============
81
82On success 0 is returned, on error -1 and the ``errno`` variable is set
83appropriately. The generic error codes are described at the
84:ref:`Generic Error Codes <gen-errors>` chapter.
85
86EBUSY
87    The request was already queued or the application queued the first
88    buffer directly, but later attempted to use a request. It is not permitted
89    to mix the two APIs.
90ENOENT
91    The request did not contain any buffers. All requests are required
92    to have at least one buffer. This can also be returned if some required
93    configuration is missing in the request.
94ENOMEM
95    Out of memory when allocating internal data structures for this
96    request.
97EINVAL
98    The request has invalid data.
99EIO
100    The hardware is in a bad state. To recover, the application needs to
101    stop streaming to reset the hardware state and then try to restart
102    streaming.
103