On Wed, Mar 06, 2013 at 11:02:47AM +0100, Hans Verkuil wrote:
> On Wed 6 March 2013 10:48:13 volok...@gmail.com wrote:
> > Hi,
> > Hans
> >
> > I found in d8077d2df184f3ef63ed9ff4579d41ca64e12855 commit,
> > that V4L2_CTRL_FLAG_VOLATILE flag was disabled for some STD controls
> > and fully disabled g_ctrl iface. So How can userspace know about changing
> > some values?
>
> VOLATILE is used when register values can change automatically (e.g. if
> autogain is on and the device regulates the gain and updates that gain
> register itself).
>
Right that!!!
there one register for all 4 channell for each of AUTOGAIN,CHROMA,RED_B,BLUE_B
reg, so if one channel changes CHROMA value (it changes all 4 channels),
the another channel will have cached old value, instead new (case it value have
not volatile control)
> However, testing proved that the hardware doesn't update anything when
> in autogain mode, hence volatile support isn't needed.
>
> Note that the control framework always caches the last control value,
> so to get non-volatile controls the framework just returns that cached
> value.
>
> Regards,
>
> Hans
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