Red Hat Bugzilla – Bug 445110
kudzu ddc autoprobe monitor detection fails, affects xorg display
Last modified: 2009-01-09 02:48:23 EST
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Description of problem:
My monitor, a Dell M782 attached to an nvidia NV18, is no longer auto-detected by ddcprobe, the fedora version of which relies on kudzu for its auto-detection. This resulted in my xorg display being drawn at a low resolution and low refresh rate (which I am not fond of).
Version-Release number of selected component (if applicable):
Steps to Reproduce:
With a Dell M782 monitor connected:
1. In bash, run /usr/sbin/ddcprobe. Note the output:
Monitor autoprobe results
Monitor autoprobe failed.
2. service restart kudzu; less /etc/sysconfig/hwconf . Note the lack of any monitor detection.
3. Configure xorg.conf to use auto-probed monitor results, by removing or commenting out any "Monitor" section references. Restart gdm, and watch the login area take up your entire screen as it falls back to a low video resolution @ 60Hz.
I never had to intentionally reproduce this problem. It happened spontaneously, and I was able to trace the problem back to ddcprobe, which relies on kudzu. By placing a static Monitor definition for my monitor in my xorg.conf, I was able to work around the unexpected monitor hardware probe failure.
Kudzu and ddcprobe should have continued to properly auto-detect my monitor, as has been the case until recently, with xorg utilizing that information as it had been.
I suspect a recent update broke something. For the last several months, I've been running my desktop @ 1280x1024x24x75 without a monitor definition in my xorg.conf. When I logged out this morning, the gdm login came back up looking big and all flickery (yes, that's my word, and it is copylefted). As a workaround, I was able to gather some info for my monitor from an older Xorg.log file (where the auto-probe had succeeded), and then create the necessary monitor definition in xorg.conf. My desktop looks better now.
During the course of troubleshooting:
I have confirmed that this is not a hardware failure. I booted a ubuntu livecd, and ran ddcprobe from a shell prompt. The proper information for my video card and monitor were returned, the output of which I shall try to attach. My monitor is not auto-detected in fedora whether I am using the proprietary nvidia driver or the free software nv driver. The ubuntu ddcprobe data was obtained while the free nv driver was loaded there.
I have also checked that there is an entry for my Dell M782 monitor in the hwdata MonitorsDB, and that looks fine.
In the ddcprobe python script, an empty list is returned from the call to kudzu.probe() in line 65. I haven't had time to go any further into the source code than that, but the early indicators seem to be pointing in the direction of kudzu or the python wrapper module.
There appear to be two other bugs, most likely related to this: bug #230566 and bug #247271, but they're categorized (possibly erroneously) as xorg-related. However, they are relatively old, and the problem I'm having just started recently. Jeez... have I missed anything!?
Created attachment 304467 [details]
proper ddcprobe functional output
This information was gathered and is being reported as described in the initial
bug report post.
X doesn't use kudzu for its internal DDC code. Assigning to the X server.
That may be so, but that doesn't change the fact that kudzu ddc monitor probing
is broken, and, by extension /usr/sbin/ddcprobe, since it's a python wrapper for
that subsystem. This auto-detection should be occurring well before X starts.
Maybe we have two bugs here?
It may be broken, but:
- any X auto-monitor configuration is entirely separate
- kudzu is more or less removed from all codepaths in Fedora 9, so it's unlikely
that any changes will be backported there
We don't use the output of ddcprobe for anything. And in F9, it no longer even
The more interesting question is why X didn't figure out the DDC info on its
own. Can you attach your /var/log/Xorg.0.log please?
Created attachment 304586 [details]
Thanks for helping out with this, guys. I really do appreciate it.
Since I've recently added the static monitor definition to xorg.conf, I'm not
exactly certain as to which Xorg log file would be best to submit to you (and
I'm actually too tired to go look and figure that out right now). But, since all
the log files in the rotation are only ~180K, you can have all 5 of them.
Created attachment 304587 [details]
Created attachment 304588 [details]
Created attachment 304589 [details]
Created attachment 304590 [details]
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