Dell laptop X ddcprobe redhat-config-xfree86 problem solved!

Dell laptop X ddcprobe redhat-config-xfree86 problem solved!

Post by Krell » Wed, 04 Jun 2003 13:54:30


I recently had to experience setting up a Dell laptop with Red Hat 9.
It couldn't start X properly.  So, I used text mode install.  This
worked OK.  It installed successfully and I got a working system in
text mode.  I then tried to configure X, and it would not work.  I was
able to get it to eventually work, though, and here's what I did.  I'm
posting this here so that anybody else having similar problems might
want to try the same thing.


The ddcprobe program fails to detect the DDC monitor timing
information coming from the monitor.  Since this laptop uses a flat
panel screen, this shouldn't matter.  The video card (ATI Rage 128
Mobility) was detected perfectly, though.

Unfortunately, this failure causes the redhat-config-xfree86 program
to fail.  It demands proper timing information in order to build the
modelines inside the XF86Config file.  It complains about "ddcprobe
returned bogus values".  It won't properly build a good XF86Config
file until it gets proper results from ddcprobe, so X won't run.


I modified the ddcprobe program so that instead of printing an error
message and giving up when monitor detection fails, it simply returns
hardcoded values.  I was able to figure out just enough Python to get
it to work (struggling with evil whitespace-dependent syntax).

Here's what I chose: horizontal sync rate 30-90, vertical sync rate
40-120, physical size 400x300, and for the string fields I simply put
"Unknown".  I just made these values up, and it seemed to work!

I ran the redhat-config-xfree86 program again, and after a fairly long
delay, the configuration screen came up and I was able to use X!  In
order to get the best picture quality, the values needed to be tweaked
to something more correct than my wild guesses, but at least this
worked well enough to get in, and I could use the GUI to make final
adjustments to the values.

I highly recommend that Red Hat please make this the default behaviour
for ddcprobe, so that people who don't have fully DDC-compliant
monitors can still be able to install and use X correctly.  However, I
would change my values to whatever the old IBM VGA monitor standards
were, to guarantee compatibility, instead of using my wild guesses.

If anyone wants my modified ddcprobe program, just ask me.  Please
email to krellan=at=krellan-dot-com (spam-filtered email address).



1. Dell Inspiron 2600 Laptop + RedHat 7.3 + XFree86 4.2 = bad refresh rate

I managed to get XFree up and running on my laptop, but I'm running into
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all blurred. I have to move the window off the screen and slowly move it
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