1.. SPDX-License-Identifier: GPL-2.0 OR GFDL-1.1-no-invariants-or-later 2.. c:namespace:: MC 3 4.. _media_request_ioc_queue: 5 6***************************** 7ioctl MEDIA_REQUEST_IOC_QUEUE 8***************************** 9 10Name 11==== 12 13MEDIA_REQUEST_IOC_QUEUE - Queue a request 14 15Synopsis 16======== 17 18.. c:macro:: MEDIA_REQUEST_IOC_QUEUE 19 20``int ioctl(int request_fd, MEDIA_REQUEST_IOC_QUEUE)`` 21 22Arguments 23========= 24 25``request_fd`` 26 File descriptor returned by :ref:`MEDIA_IOC_REQUEST_ALLOC`. 27 28Description 29=========== 30 31If the media device supports :ref:`requests <media-request-api>`, then 32this request ioctl can be used to queue a previously allocated request. 33 34If the request was successfully queued, then the file descriptor can be 35:ref:`polled <request-func-poll>` to wait for the request to complete. 36 37If the request was already queued before, then ``EBUSY`` is returned. 38Other errors can be returned if the contents of the request contained 39invalid or inconsistent data, see the next section for a list of 40common error codes. On error both the request and driver state are unchanged. 41 42Once a request is queued, then the driver is required to gracefully handle 43errors that occur when the request is applied to the hardware. The 44exception is the ``EIO`` error which signals a fatal error that requires 45the application to stop streaming to reset the hardware state. 46 47It is not allowed to mix queuing requests with queuing buffers directly 48(without a request). ``EBUSY`` will be returned if the first buffer was 49queued directly and you next try to queue a request, or vice versa. 50 51A request must contain at least one buffer, otherwise this ioctl will 52return an ``ENOENT`` error. 53 54Return Value 55============ 56 57On success 0 is returned, on error -1 and the ``errno`` variable is set 58appropriately. The generic error codes are described at the 59:ref:`Generic Error Codes <gen-errors>` chapter. 60 61EBUSY 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 64 to mix the two APIs. 65ENOENT 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. 69ENOMEM 70 Out of memory when allocating internal data structures for this 71 request. 72EINVAL 73 The request has invalid data. 74EIO 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 77 streaming. 78