linux-kernel - Re: [Linux-fbdev-devel] [RFC] driving a LCD panel via I2C

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Message-Id: <1190674984.19359.114.camel@localhost.localdomain>
Date:	Tue, 25 Sep 2007 00:03:04 +0100
From:	Richard Purdie <rpurdie@...ys.net>
To:	Haavard Skinnemoen <hskinnemoen@...el.com>
Cc:	linux-fbdev-devel@...ts.sourceforge.net, giometti@...eenne.com,
	i2c@...sensors.org, linux-kernel@...r.kernel.org
Subject: Re: [Linux-fbdev-devel] [RFC] driving a LCD panel via I2C

On Mon, 2007-09-24 at 12:34 +0200, Haavard Skinnemoen wrote: 
> On Mon, 24 Sep 2007 10:58:08 +0200 (CEST)
> "Rodolfo Giometti" <giometti@...eenne.com> wrote:
> > I have an LCD panel on a custom PXA27x based board and it must be
> > turned on/off by some special commands via a GPIO throught a I2C chip.
> > 
> > I'd like some suggestion about I can easily manage this situation.
> 
> I have a similar panel in the sense that it needs a bunch of SPI
> commands to get started. I implemented a LCD driver
> (drivers/video/backlight) for it so that it is automatically turned
> on/off at bootup/shutdown, and can be manually turned on/off
> through /sys/class/lcd/ltv350qv/power. AFAIK the driver is currently
> sitting in the backlight tree scheduled for inclusion in 2.6.24.

It is, its queued as
http://git.o-hand.com/?p=linux-rpurdie-backlight;a=commitdiff;h=c962fe18c64ae9139028ee674ab3c380449ce052

Its also worth noting that corgi-bl.c has a variant (akita) that uses a
gpio over an I2C IO expander for the backlight control. The code paths
are a little convoluted since other gpios are used by other drivers. The
base driver is in arch/arm/mach-pxa/akita-ioexp.c, the set_intensity
function is in arch/arm/mach-pxa/corgi_lcd.c and the base backlight
device in arch/arm/mach-pxa/spitz.c. I will be moving the set_intensity
to spitz.c to make things a little clearer.

Also, I'm in the process of turning corgi-bl.c into a generic backlight
driver which might help you, see:

http://git.o-hand.com/?p=linux-rpurdie-backlight;a=commitdiff;h=c74f241bf53bf5251c7c10f65041c20979f6c694

Now, the GPIO framework could help too (it didn't exist when I wrote
akita-ioexp)...

Regards,

Richard

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