diff options
-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 | |||
44 | flags. When the function timed out it returns a value of zero, on | 44 | flags. When the function timed out it returns a value of zero, on |
45 | failure it returns <returnvalue>-1</returnvalue> and the | 45 | failure it returns <returnvalue>-1</returnvalue> and the |
46 | <varname>errno</varname> variable is set appropriately. When the | 46 | <varname>errno</varname> variable is set appropriately. When the |
47 | application did not call &VIDIOC-QBUF; or &VIDIOC-STREAMON; yet the | 47 | application did not call &VIDIOC-STREAMON; the |
48 | <function>poll()</function> function succeeds, but sets the | 48 | <function>poll()</function> function succeeds, but sets the |
49 | <constant>POLLERR</constant> flag in the | 49 | <constant>POLLERR</constant> flag in the |
50 | <structfield>revents</structfield> field.</para> | 50 | <structfield>revents</structfield> field. When the |
51 | application has called &VIDIOC-STREAMON; for a capture device but hasn't | ||
52 | yet called &VIDIOC-QBUF;, the <function>poll()</function> function | ||
53 | succeeds and sets the <constant>POLLERR</constant> flag in the | ||
54 | <structfield>revents</structfield> field. For output devices this | ||
55 | same situation will cause <function>poll()</function> to succeed | ||
56 | as well, but it sets the <constant>POLLOUT</constant> and | ||
57 | <constant>POLLWRNORM</constant> flags in the <structfield>revents</structfield> | ||
58 | field.</para> | ||
51 | 59 | ||
52 | <para>When use of the <function>read()</function> function has | 60 | <para>When use of the <function>read()</function> function has |
53 | been negotiated and the driver does not capture yet, the | 61 | been negotiated and the driver does not capture yet, the |