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

[Sascha Hauer <s.hauer@pengutronix.de>]

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@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?

Sascha

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