[UPSTREAM] Move backlight handling out of pcf50633 driver

[Balaji Rao]

On Tue, Oct 21, 2008 at 10:04:15AM +0100, Mark Brown wrote:
> On Tue, Oct 21, 2008 at 08:41:55AM +0530, Balaji Rao wrote:
> 
> > The voltage change effected by changing the brigtness value in /sys is
> > exponential, not linear.. So, the code that assumes that it's going to
> > reduce the brightness level by half by making it 30 or so, is actually
> > reducing it by 1/6 th.
> 
> The human eye doesn't detect brightness linearly so hardware intended
> for use in controlling brightness often implements controls with
> non-linear values like this - check what the actual effect is for the
> user.
> 

I changed to code to scale brigtness linearly between 0-255 and the
result was not good. Now I've come to understand that brigtness does not
vary linearly with the voltage. :)

Thank you,

	- Balaji