78 lines
2.5 KiB
ReStructuredText
78 lines
2.5 KiB
ReStructuredText
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.. SPDX-License-Identifier: GPL-2.0 OR GFDL-1.1-no-invariants-or-later
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.. c:namespace:: MC
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.. _media_request_ioc_queue:
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*****************************
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ioctl MEDIA_REQUEST_IOC_QUEUE
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*****************************
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Name
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====
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MEDIA_REQUEST_IOC_QUEUE - Queue a request
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Synopsis
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========
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.. c:macro:: MEDIA_REQUEST_IOC_QUEUE
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``int ioctl(int request_fd, MEDIA_REQUEST_IOC_QUEUE)``
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Arguments
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=========
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``request_fd``
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File descriptor returned by :ref:`MEDIA_IOC_REQUEST_ALLOC`.
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Description
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===========
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If the media device supports :ref:`requests <media-request-api>`, then
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this request ioctl can be used to queue a previously allocated request.
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If the request was successfully queued, then the file descriptor can be
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:ref:`polled <request-func-poll>` to wait for the request to complete.
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If the request was already queued before, then ``EBUSY`` is returned.
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Other errors can be returned if the contents of the request contained
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invalid or inconsistent data, see the next section for a list of
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common error codes. On error both the request and driver state are unchanged.
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Once a request is queued, then the driver is required to gracefully handle
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errors that occur when the request is applied to the hardware. The
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exception is the ``EIO`` error which signals a fatal error that requires
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the application to stop streaming to reset the hardware state.
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It is not allowed to mix queuing requests with queuing buffers directly
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(without a request). ``EBUSY`` will be returned if the first buffer was
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queued directly and you next try to queue a request, or vice versa.
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A request must contain at least one buffer, otherwise this ioctl will
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return an ``ENOENT`` error.
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Return Value
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============
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On success 0 is returned, on error -1 and the ``errno`` variable is set
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appropriately. The generic error codes are described at the
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:ref:`Generic Error Codes <gen-errors>` chapter.
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EBUSY
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The request was already queued or the application queued the first
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buffer directly, but later attempted to use a request. It is not permitted
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to mix the two APIs.
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ENOENT
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The request did not contain any buffers. All requests are required
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to have at least one buffer. This can also be returned if some required
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configuration is missing in the request.
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ENOMEM
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Out of memory when allocating internal data structures for this
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request.
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EINVAL
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The request has invalid data.
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EIO
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The hardware is in a bad state. To recover, the application needs to
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stop streaming to reset the hardware state and then try to restart
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streaming.
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