[Xorg] DDC/CI, need advice on implementation

Jon Smirl jonsmirl at yahoo.com
Mon Jul 5 14:54:33 PDT 2004

Does the fbdev driver for your card have a kernel level I2C driver? For
example matrox and radeon have this already. In that case you can load
the i2c-dev driver and control the bus from simple user space apps. 

If not, it might be simpler to implement a kernel I2C driver for your
card than to mess around with the one in xfree. It is not hard to make
one, just look at the kernel driver for Matrox (mga) and the xfree
source code. That will provide everything you need to build your own.

--- Nicolas Boichat <nicolas at boichat.ch> wrote:
> Hello
> I reverse-engineered a part of the DDC/CI protocol. This protocol is
> used to control a monitor by software, without using the OSD.
> I'll soon write some web pages explaining what I did to
> reverse-engineer
> it, and on the protocol itself.
> I modified the DDC driver
> (xc/programs/Xserver/hw/xfree86/ddc/xf86DDC.c), because it is the
> easiest place to get access to the graphics card I2C bus (DDC2 and
> DDC/CI are located on the same I2C bus), and I'm now able to read
> values
> from my Mitsubishi Diamond Pro 2060u (I mean read contrast,
> brightness,
> red, green and blue levels for example), but I still can't write
> values
> (I don't think I'm very far).
> Now I have a problem, I need to have access to the DDC/CI bus from an
> external application, because, of course, I don't want to change the
> monitor parameters only when the server loads.
> I don't know much about XFree/Xorg, so I need your help:
>  - Should I create a new shared library in xc/lib? (for example
> Xxf86ddcci)
>  - Or Should I add functions to an existing library ? (in this case,
> which one? Xxf86vm? Xxf86misc?)
>  - Or should I do something else??
> I would like to add in this library simple wrappers to functions that
> are in I2C and DDC modules, is it possible and well designed ?
> I hope I've been clear enough, if it is not the case please ask me.
> Best regards,
> Nicolas Boichat
> _______________________________________________
> xorg mailing list
> xorg at freedesktop.org
> http://freedesktop.org/mailman/listinfo/xorg

Jon Smirl
jonsmirl at yahoo.com

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