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Commit acf92046 authored by Hans Verkuil's avatar Hans Verkuil Committed by Mauro Carvalho Chehab
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[media] DocBook media: fix the poll() 'no QBUF' documentation 



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: default avatarHans Verkuil <hans.verkuil@cisco.com>
Acked-by: default avatarLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab@osg.samsung.com>
parent 58d75f4b

Documentation/DocBook/media/v4l/func-poll.xml

+10 −2
Original line number Diff line number Diff line
@@ -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