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SubjectRe: [PATCH v2 1/5] media/v4l2-ctrls: volatiles should not generate CH_VALUE
Hello Laurent

On Tue, Apr 21, 2015 at 7:44 PM, Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
> Hi Ricardo,
>
> Thank you for the patch, and sorry for the late review (so late that the patch
> has already been merged).

No worries.

>
> On Friday 20 March 2015 14:30:46 Ricardo Ribalda Delgado wrote:
>> Volatile controls should not generate CH_VALUE events.
>
> What's the rationale for that ? I would actually expect the value change
> events to be more useful for volatile controls than non-volatile controls.
> Volatile controls can have their value changed by the hardware without
> software intervention, and it makes sense to me to report that to userspace.

Imagine a temperature register on the sensor. It is changing
constantly, resolution 10 milidegrees:

Do you want to get an event for every change? Who will poll the
temperature? The driver? The hardware will irq the driver....?

So I guess the less wrong solution is not throwing the ch_value event.

This is just my two cents, probably Hans has a much better global view :)

Regards.


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