Messages in this thread | | | From | Ricardo Ribalda Delgado <> | Date | Tue, 21 Apr 2015 23:32:18 +0200 | Subject | Re: [PATCH v2 1/5] media/v4l2-ctrls: volatiles should not generate CH_VALUE |
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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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