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Date: Mon, 17 Feb 2014 09:43:22 +0100
From: Hans Verkuil <hverkuil@xs4all.nl>
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To: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
CC: Sakari Ailus <sakari.ailus@iki.fi>, linux-media@vger.kernel.org,
	k.debski@samsung.com
Subject: Re: [PATCH v5 7/7] v4l: Document timestamp buffer flag behaviour
References: <1392497585-5084-1-git-send-email-sakari.ailus@iki.fi> <1392497585-5084-8-git-send-email-sakari.ailus@iki.fi> <52FFD60B.4080308@xs4all.nl> <1640658.PZi431b47s@avalon>
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On 02/17/2014 01:56 AM, Laurent Pinchart wrote:
> Hello,
> 
> On Saturday 15 February 2014 22:03:07 Hans Verkuil wrote:
>> On 02/15/2014 09:53 PM, Sakari Ailus wrote:
>>> Timestamp buffer flags are constant at the moment. Document them so that
>>> 1) they're always valid and 2) not changed by the drivers. This leaves
>>> room to extend the functionality later on if needed.
>>>
>>> Signed-off-by: Sakari Ailus <sakari.ailus@iki.fi>
>>> ---
>>>
>>>  Documentation/DocBook/media/v4l/io.xml |   10 ++++++++++
>>>  1 file changed, 10 insertions(+)
>>>
>>> diff --git a/Documentation/DocBook/media/v4l/io.xml
>>> b/Documentation/DocBook/media/v4l/io.xml index fbd0c6e..4f76565 100644
>>> --- a/Documentation/DocBook/media/v4l/io.xml
>>> +++ b/Documentation/DocBook/media/v4l/io.xml
>>> @@ -653,6 +653,16 @@ plane, are stored in struct
>>> <structname>v4l2_plane</structname> instead.> 
>>>  In that case, struct <structname>v4l2_buffer</structname> contains an
>>>  array of plane structures.</para>
>>>
>>> +    <para>Dequeued video buffers come with timestamps. These
>>> +    timestamps can be taken from different clocks and at different
>>> +    part of the frame, depending on the driver. Please see flags in
>>
>> s/part/parts/
>>
>> But I think I would write it somewhat differently:
>>
>> "The driver decides at which part of the frame and with which clock
>> the timestamp is taken."
>>
>>> +    the masks <constant>V4L2_BUF_FLAG_TIMESTAMP_MASK</constant> and
>>> +    <constant>V4L2_BUF_FLAG_TSTAMP_SRC_MASK</constant> in <xref
>>> +    linkend="buffer-flags">. These flags are guaranteed to be always
>>> +    valid and will not be changed by the driver autonomously.
> 
> This sentence sounds a bit confusing to me. What about
> 
> "These flags are always valid and are constant across all buffers during the 
> whole video stream."

I like this.

Regards,

	Hans