linux-kernel - Re: DDC on Thinkpad x220

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Date:   Tue, 1 Oct 2019 13:43:30 +0200
From:   Pavel Machek <pavel@....cz>
To:     Jani Nikula <jani.nikula@...ux.intel.com>
Cc:     kernel list <linux-kernel@...r.kernel.org>,
        intel-gfx@...ts.freedesktop.org, rodrigo.vivi@...el.com,
        joonas.lahtinen@...ux.intel.com
Subject: Re: DDC on Thinkpad x220

On Tue 2019-10-01 12:39:34, Jani Nikula wrote:
> On Mon, 30 Sep 2019, Pavel Machek <pavel@....cz> wrote:
> > Hi!
> >
> > Thinkpad X220 should be new enough machine to talk DDC to the
> > monitors, right? And my monitor has DDC enable/disable in the menu, so
> > it should support it, too...
> >
> > But I don't have /dev/i2c* and did not figure out how to talk to the
> > monitor. Is the support there in the kernel? What do I need to enable
> > it?
> 
> # modprobe i2c-dev

Thanks!

I enabled I2C_CHARDEV, and installed ddccontrol:

c   ddccontrol                      - program to control monitor

I can read parameters of Dell monitor on VGA:

sudo ddccontrol dev:/dev/i2c-1 -c -d
/usr/share/ddccontrol-db/monitor/DELA013.xml
Control 0x10: +/79/100   [???] -- brightness
Control 0x12: +/63/100   [???] -- contrast

Unfortunately the Fujitsu monitor does not seem to
communicate. Fujitsu is my main monitor :-(.

pavel@duo:~$ sudo ddccontrol dev:/dev/i2c-4 -c -d
ddccontrol version 0.4.2
Copyright 2004-2005 Oleg I. Vdovikin (oleg@...msu.su)
Copyright 2004-2006 Nicolas Boichat (nicolas@...chat.ch)
This program comes with ABSOLUTELY NO WARRANTY.
You may redistribute copies of this program under the terms of the GNU
General Public License.

Reading EDID and initializing DDC/CI at bus dev:/dev/i2c-4...
ioctl(): No such device or address
ioctl returned -1
ioctl(): No such device or address
ioctl returned -1
ioctl(): No such device or address
ioctl returned -1
I/O warning : failed to load external entity
"/usr/share/ddccontrol-db/monitor/FUS080A.xml"
Document not parsed successfully.
ioctl(): No such device or address
ioctl returned -1

DDC/CI at dev:/dev/i2c-4 is unusable (-1).
If your graphics card need it, please check all the required kernel
modules are loaded (i2c-dev, and your framebuffer driver).

Any further hints?

Thanks and best regards,
								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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