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There is a problem with mainboard Asus M2A-VM. There is no HDMI monitor 
connected (monitor uses DVI) but the kernel still tries to read the EDID. Thus, 
dmesg is spammed every 10 seconds with this message:
[   21.383270] [drm:drm_edid_block_valid] *ERROR* Raw EDID:
[   21.383305] <3>00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  
................
[   21.383307] <3>00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  
................
[   21.383310] <3>00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  
................
[   21.383312] <3>00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  
................
[   21.383314] <3>00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  
................
[   21.383317] <3>00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  
................
[   21.383319] <3>00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  
................
[   21.383322] <3>00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  
................
[   21.383324] 
[   21.383328] radeon 0000:01:05.0: HDMI-A-1: EDID block 0 invalid.
[   21.383332] [drm:radeon_dvi_detect] *ERROR* HDMI-A-1: probed a monitor but 
no|invalid EDID

X behaves very jerky because of the load caused by the kernel demanding the 
EDID every 10 seconds.
For more info see https://bugzilla.redhat.com/show_bug.cgi?id=668196 and 
http://ubuntuforums.org/showthread.php?t=1607778

I found three possible solutions to solve my problem:
1) disable KMS by using the kernel parameter "radeon.modeset=0"
Unfortunately, the X server will then segfault after a short time
2) get the kernel source and patch the radeon driver, see 
http://ubuntuforums.org/showthread.php?t=1607778
(the patch is not from me!)
this works, but you have to patch the kernel after every update again
3) execute the command
"echo -n N > /sys/module/drm_kms_helper/parameters/poll"
This will effectively stop the pollution of the dmesg (and all the quirky X 
behavior). This option does not exist in kernel 2.6.35 that's why I had update 
to kernel 2.6.38

It would be fine if the kernel tries to read the EDID only once and then
stops trying if it fails (see patch from solution #2).

** Affects: linux
     Importance: Undecided
         Status: Fix Released

** Affects: linux (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: kj-triage
-- 
Asus M2A-VM: kernel demanding EDID for an unconnected monitor
https://bugs.launchpad.net/bugs/722806
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