From: Hans Verkuil <hans.verkuil@xxxxxxxxx>
Clarify what poll() returns if STREAMON was called but not QBUF.
Make explicit the different behavior for this scenario for
capture and output devices.
Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
---
Documentation/DocBook/media/v4l/func-poll.xml | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/Documentation/DocBook/media/v4l/func-poll.xml b/Documentation/DocBook/media/v4l/func-poll.xml
index 85cad8b..b7ed9e8 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 calls &VIDIOC-STREAMON; for a capture device without a
+preceeding &VIDIOC-QBUF; the <function>poll()</function> function
+succeeds, but 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
--
2.1.0
--
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