diff --git a/Documentation/DocBook/media/v4l/func-poll.xml b/Documentation/DocBook/media/v4l/func-poll.xml index 85cad8bff5ba..bd07104a35e9 100644 --- a/Documentation/DocBook/media/v4l/func-poll.xml +++ b/Documentation/DocBook/media/v4l/func-poll.xml @@ -44,10 +44,18 @@ Capture devices set the POLLIN and flags. When the function timed out it returns a value of zero, on failure it returns -1 and the errno variable is set appropriately. When the -application did not call &VIDIOC-QBUF; or &VIDIOC-STREAMON; yet the +application did not call &VIDIOC-STREAMON; the poll() function succeeds, but sets the POLLERR flag in the -revents field. +revents field. When the +application has called &VIDIOC-STREAMON; for a capture device but hasn't +yet called &VIDIOC-QBUF;, the poll() function +succeeds and sets the POLLERR flag in the +revents field. For output devices this +same situation will cause poll() to succeed +as well, but it sets the POLLOUT and +POLLWRNORM flags in the revents +field. When use of the read() function has been negotiated and the driver does not capture yet, the