I just stumbled over some strange behavior, and it definitely changed past Xserver 1.4.0 (don't know the exact version yet, bisecting this would be probably worth it). A snippet of the config I'm testing is Section "Monitor" Identifier "M1" EndSection Section "Monitor" Identifier "M2" Option "Right-Of" "M1" EndSection Section "Device" Identifier "D" Driver "radeonhd" Option "monitor-DVI-I_1/digital" "M1" Option "monitor-DVI-I_2/digital" "M2" EndSection Section "Screen" [...] Identifier "S" Device "D" Monitor "M1" EndSection [...] So basically a static multi-monitor setup for RandR 1.2, with one of the monitors additionally referenced in the Screen section. This monitor reference shouldn't be used at all, because the driver sets use_screen_monitor to FALSE for all outputs. This used to work - however, beginning with 1.4.90 the multi-monitor setup fails if and only if I use the two digital DVI outputs on this card, with DVI and VGA it works fine, with DVI/d and DVI/a it also works fine. If I remove the reference to the M1 monitor in the Screen section it works fine. If I add another monitor and reference it in the Screen section instead it works fine. It's probably difficult to reproduce this with another driver, but this shouldn't be a driver issue. Does anybody have a clue WTF is going on here, is this considered standard behavior or rather a bug? If it's standard, why is its behavior depending on the outputs (and not on the monitors)? - Mailed on xorg-devel: Date: Thu, 13 Mar 2008 18:55:44 +0100 From: Matthias Hopf <mhopf@suse.de> To: xorg@lists.freedesktop.org Subject: RandR: multi-referenced monitor sections & problems with them
This bug is tracked for openSUSE in https://bugzilla.novell.com/show_bug.cgi?id=370656
Stefan Dirsch: Nearly the same problem with nv driver on G80. As long as Monitor "M1" in Section Screen is not removed/commented out, the monitors cannot be positioned side by side with the error message similar to this: (EE) Monitor(1) cannot be positioned right of Monitor[0] without a mode specified. Specifying modes explicitetly for both monitor doesn't help at all. Only the workaround mentioned above does.
*** Bug 15142 has been marked as a duplicate of this bug. ***
Apparently, the Screen section monitor is assigned to the first output. In this case this happened to be TV_7PIN_DIN. So adding Option "monitor-TV_7PIN_DIN" "M1" instead had the same effect. This is actually a driver issue, fixed in radeonhd in the meantime. Fixing the base issue is probably not. Monitors are not to be used by multiple instances, because the mode pool between then would be shared. I.e. if one is disconnected, the other one won't see any modes, which is the base issue of this bug.
Mass closure: This bug has been untouched for more than six years, and is not obviously still valid. Please file a new report if you continue to experience issues with a current server.
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