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-rw-r--r--Documentation/DocBook/media/v4l/func-poll.xml12
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
44flags. When the function timed out it returns a value of zero, on 44flags. When the function timed out it returns a value of zero, on
45failure it returns <returnvalue>-1</returnvalue> and the 45failure 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
47application did not call &VIDIOC-QBUF; or &VIDIOC-STREAMON; yet the 47application 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
51application has called &VIDIOC-STREAMON; for a capture device but hasn't
52yet called &VIDIOC-QBUF;, the <function>poll()</function> function
53succeeds and sets the <constant>POLLERR</constant> flag in the
54<structfield>revents</structfield> field. For output devices this
55same situation will cause <function>poll()</function> to succeed
56as well, but it sets the <constant>POLLOUT</constant> and
57<constant>POLLWRNORM</constant> flags in the <structfield>revents</structfield>
58field.</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
53been negotiated and the driver does not capture yet, the 61been negotiated and the driver does not capture yet, the