diff options
Diffstat (limited to 'Documentation/DocBook')
| -rw-r--r-- | Documentation/DocBook/media/v4l/func-poll.xml | 12 |
1 files changed, 10 insertions, 2 deletions
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 <constant>POLLIN</constant> and flags. When the function timed out it returns a value of zero, on failure it returns <returnvalue>-1</returnvalue> and the <varname>errno</varname> variable is set appropriately. When the -application did not call &VIDIOC-QBUF; or &VIDIOC-STREAMON; yet the +application did not call &VIDIOC-STREAMON; the <function>poll()</function> function succeeds, but sets the <constant>POLLERR</constant> flag in the -<structfield>revents</structfield> field.</para> +<structfield>revents</structfield> field. When the +application has called &VIDIOC-STREAMON; for a capture device but hasn't +yet called &VIDIOC-QBUF;, the <function>poll()</function> function +succeeds and sets the <constant>POLLERR</constant> flag in the +<structfield>revents</structfield> field. For output devices this +same situation will cause <function>poll()</function> to succeed +as well, but it sets the <constant>POLLOUT</constant> and +<constant>POLLWRNORM</constant> flags in the <structfield>revents</structfield> +field.</para> <para>When use of the <function>read()</function> function has been negotiated and the driver does not capture yet, the |