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<div>Dear Jim:</div>
<div><br></div>
<div>Thanks much.</div>
<div>To give some idea of why these controls could be important for
kids, see the attached.</div>
<div><br></div>
<div>Bob</div>
<div><br></div>
<div><br></div>
<div><br></div>
<div>At 10:41 AM -0400 10/3/06, jg@laptop.org wrote:</div>
<blockquote type="cite" cite><font face="Geneva" color="#000000">On
Tue, 2006-10-03 at 08:31 -0600, Jonathan Corbet wrote:<br>
> Jim Gettys <jg@laptop.org> wrote:<br>
><br>
> > To do so, they need to be<br>
> > able to use the device in as linear a fashion
(photometrically) as<br>
> > possible: disable gain control, black point processing,
color balancing,<br>
> > etc, which from looking at the sensor spec appears to be
possible from a<br>
> > quick perusal. Such sensors do a remarkable amount of
signal processing<br>
> > internally these days.<br>
> ><br>
> > I know V4L has facilities for controlling (most of) these
features, that<br>
> > you are hooking up in the sensor driver right now.
Does V4L also have<br>
> > facilities for completely disabling these features?
Are there any<br>
> > features of the chip that V4L does not support?<br>
><br>
> V4L2 has a fair number of predefined controls, there's a list
at:<br>
><br>
> </font><a
href="http://v4l2spec.bytesex.org/spec/x488.htm#CONTROL-ID"><font
face="Geneva"
color="#000000">http://v4l2spec.bytesex.org/spec/x488.htm#CONTROL-ID</font
></a><font face="Geneva" color="#000000"><br>
><br>
> Some of them do what they want - disabling white balance, auto
exposure<br>
> control, etc. There is also a way to add driver-specific
controls for<br>
> the ones that are missing. So all of this can be
handled.<br>
><br>
> If it seems that any of those settings should be turned into
standard<br>
> V4L2 controls, that's easy enough to make happen.<br>
><br>
> The big challenge is a story you've heard from me for a
while:<br>
> translating those controls into an appropriate set of OV7670
register<br>
> settings. I have come to the conclusion that those settings
really<br>
> constitute a form of opaque firmware, and, without cooperation
from<br>
> OmniVision, they can be hard to get right. There's a lot of
registers<br>
> simply marked "reserved" in the spec, and there are
undocumented<br>
> ordering issues as well. It can all be done,
eventually.<br>
<br>
OK, let's get you hooked up with OmniVision. I expect we can get
their<br>
attention.<br>
<span
></span
> <span
></span
> <span
></span> - Jim<br>
<br>
--<br>
Jim Gettys<br>
One Laptop Per Child</font></blockquote>
<div><br></div>
<div><br></div>
<x-sigsep><pre>--
</pre></x-sigsep>
<div>Dr. Robert Tinker, president<br>
<br>
The Concord Consortium<br>
25 Love Ln.<br>
Concord, MA 01742<br>
978 405 3200 (general number)<br>
978 405 2076 (general fax)<br>
<br>
Find out about all our free software at
http://www.concord.org/publications/newsletter/2005-spring/opensource<span
></span>.html<br>
Realizing the educational potential of technology.<br>
http://concord.org</div>
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