Re: [PATCH 2/2] video: imxfb: Add feature to setup PWM Contrast Control Register

[Alexander Shiyan]

> On Thu, Jul 25, 2013 at 09:20:53PM +0400, Alexander Shiyan wrote:
> > On Thu, 25 Jul 2013 15:38:56 +0200
> > Markus Pargmann <mpa at pengutronix.de> wrote:
> > 
> > > Hi,
> > > 
> > > On Sun, Jul 21, 2013 at 12:35:09PM +0400, Alexander Shiyan wrote:
> > > > This patch adds feature to setup PWM Contrast Control Register.
> > > > This register is used to control the signal output at the contrast pin,
> > > > which controls contrast of the LCD panel.
> > > 
> > > http://www.spinics.net/lists/linux-fbdev/msg10002.html
> > 
> > PWM? I can not understand how the PWM driver will be connected to the
> > framebuffer driver. It is not backlight, this is contrast.
> > Even if we imagine that the driver will be connected through phandle,
> > then we will need to have at least 4! additional parameters in the framebuffer
> > driver: freq source, frequency and active pulse period + phandle to PWM.
> > Is it worth it, given that these parameters should not be adjustable?
> > On my opinion, the only one additional parameter in framebuffer is enough.
> > Thanks.
> 
> Why should the contrast of a display not be adjustable?

I still can not understand the interface through which it can be changed.
Same as how the default settings can be passed to the framebuffer driver.

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