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 :)
Regards,
Hans
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