Re: Some comments on the new autocluster patches

[Hans de Goede <hdegoede@redhat.com>]

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