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	Tue, 26 Jul 2011 10:39:12 -0400
From: Hans Verkuil <hverkuil@xs4all.nl>
To: Hans de Goede <hdegoede@redhat.com>
Subject: Re: Some comments on the new autocluster patches
Date: Tue, 26 Jul 2011 16:39:00 +0200
Cc: Hans Verkuil <hansverk@cisco.com>,
	Linux Media Mailing List <linux-media@vger.kernel.org>
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On Tuesday, July 26, 2011 16:38:19 Hans de Goede wrote:
> Hi,
> 
> On 07/26/2011 04:19 PM, Hans Verkuil wrote:
> > On Tuesday, July 26, 2011 15:51:58 Hans de Goede wrote:
> >
> 
> <snip>
> 
> >>> An open question is whether writing to an inactive and volatile control should return
> >>> an error or not.
> >>
> >> I would prefer an error return.
> >
> > I am worried about backwards compatibility, though. Right now inactive controls
> > can be written safely. Suddenly you add the volatile flag and doing the same thing
> > causes an error.
> >
> > Also, a program that saves control values will have to skip any control that:
> >
> > 1) Is read or write only
> > 2) Is inactive and volatile
> >
> > The first is obvious, but the second not so much.
> >
> > Another reason for not returning an error is that it makes v4l2-ctrls.c more complex: if
> > autogain is on and I call VIDIOC_S_EXT_CTRLS to set autogain to off and gain to a new
> > manual value, then it is quite difficult to detect that in this case setting gain is OK
> > (since autogain is turned off at the same time).
> >
> > The more I think about it, the more I think this should just be allowed. The value
> > disappears into a black hole, but at least it won't break any apps.
> 
> Ok disappear into a black hole it is :)

Good. Then I'll try to work on this this week.

Regards,

	Hans