Hi! > Document the request API for V4L2 devices, and amend the documentation > of system calls influenced by it. > > Signed-off-by: Alexandre Courbot <acourbot@xxxxxxxxxxxx> > Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx> Cc documentation people? > +Synopsis > +======== > + > +.. c:function:: int ioctl( int request_fd, MEDIA_REQUEST_IOC_QUEUE ) > + :name: MEDIA_REQUEST_IOC_QUEUE > + > + > +Arguments > +========= > + > +``request_fd`` > + File descriptor returned by :ref:`MEDIA_IOC_REQUEST_ALLOC`. > + > + > +Description > +=========== > + > +If the media device supports :ref:`requests <media-request-api>`, then > +this request ioctl can be used to queue a previously allocated request. > + > +If the request was successfully queued, then the file descriptor can be > +:ref:`polled <request-func-poll>` to wait for the request to complete. > + > +If the request was already queued before, then ``EBUSY`` is returned. I'd expect -1 to be returned and errno set to EBUSY? > +============ > + > +On success 0 is returned, on error -1 and the ``errno`` variable is set > +appropriately. The generic error codes are described at the > +:ref:`Generic Error Codes <gen-errors>` chapter. > + > +EBUSY > + The request was already queued. > +EPERM > + The application queued the first buffer directly, but later attempted > + to use a request. It is not permitted to mix the two APIs. > +ENOENT > + The request did not contain any buffers. All requests are required > + to have at least one buffer. This can also be returned if required > + controls are missing. > +ENOMEM > + Out of memory when allocating internal data structures for this > + request. > +EINVAL > + The request has invalid data. > +EIO > + The hardware is in a bad state. To recover, the application needs to > + stop streaming to reset the hardware state and then try to restart > + streaming. Pavel
