1 .. SPDX-License-Identifier: GPL-2.0 OR GFDL-1.1-no-invariants-or-later
4 .. _media_request_ioc_queue:
6 *****************************
7 ioctl MEDIA_REQUEST_IOC_QUEUE
8 *****************************
13 MEDIA_REQUEST_IOC_QUEUE - Queue a request
18 .. c:macro:: MEDIA_REQUEST_IOC_QUEUE
20 ``int ioctl(int request_fd, MEDIA_REQUEST_IOC_QUEUE)``
26 File descriptor returned by :ref:`MEDIA_IOC_REQUEST_ALLOC`.
31 If the media device supports :ref:`requests <media-request-api>`, then
32 this request ioctl can be used to queue a previously allocated request.
34 If the request was successfully queued, then the file descriptor can be
35 :ref:`polled <request-func-poll>` to wait for the request to complete.
37 If the request was already queued before, then ``EBUSY`` is returned.
38 Other errors can be returned if the contents of the request contained
39 invalid or inconsistent data, see the next section for a list of
40 common error codes. On error both the request and driver state are unchanged.
42 Once a request is queued, then the driver is required to gracefully handle
43 errors that occur when the request is applied to the hardware. The
44 exception is the ``EIO`` error which signals a fatal error that requires
45 the application to stop streaming to reset the hardware state.
47 It is not allowed to mix queuing requests with queuing buffers directly
48 (without a request). ``EBUSY`` will be returned if the first buffer was
49 queued directly and you next try to queue a request, or vice versa.
51 A request must contain at least one buffer, otherwise this ioctl will
52 return an ``ENOENT`` error.
57 On success 0 is returned, on error -1 and the ``errno`` variable is set
58 appropriately. The generic error codes are described at the
59 :ref:`Generic Error Codes <gen-errors>` chapter.
62 The request was already queued or the application queued the first
63 buffer directly, but later attempted to use a request. It is not permitted
66 The request did not contain any buffers. All requests are required
67 to have at least one buffer. This can also be returned if some required
68 configuration is missing in the request.
70 Out of memory when allocating internal data structures for this
73 The request has invalid data.
75 The hardware is in a bad state. To recover, the application needs to
76 stop streaming to reset the hardware state and then try to restart