Red Hat Bugzilla – Bug 585371
xf86DefaultModes and DMTModes should be merged
Last modified: 2010-11-15 09:52:16 EST
Description of problem:
RHEL5 included a patch, xorg-x11-server-Red-Hat-extramodes.patch, which adds ModeLines that are not included in the default Xorg server distribution. Some of these modelines enable resolutions for widescreen LCD displays which are now quite commonplace. RHEL6 Beta currently does not include these extramodes. The effect of this is such that in some cases the optimal resolution cannot be selected for a display without manually adding the ModeLine to the xorg.conf file. ModeLines are non-trivial to lookup, so it would be best to restore the ModeLines that were included in the RHEL5 distribution. One such case where the extramodes or ModeLine is required occurs when a display is attached to the system through an analog KVM which prevents the transfer of EDID data.
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1. Using 22" LCD panel, connect analog VGA connection through analog KVM switch. The KVM prevents the system from reading the EDID for the monitor, which I think normally would be used to set the correct mode. In the absence of EDID, a correctly configured ModeLine would be required (correct?)
2. Configure xorg.conf manually, attempting to select Mode "1680x1050" without specifying the associated ModeLine. The Monitor section must have a suitable HorizSync and VertRefresh for the monitor being used. Example:
HorizSync 30.0 - 81.0
VertRefresh 56.0 - 75.0
Viewport 0 0
3. Start X windows, then review /var/log/Xorg.0.log
Failure to start X windows with the requested resolution. Tested using both the provided nouveau driver and the proprietary nvidia driver. Without the required modeline, each driver auto-selects a display resolution lower than the required value. Nouveau selects 1600x1200, nvidia selects 1024x768.
Expect same results as in RHEL5. If the Monitor section is configured with an appropriate HorizSync and VertRefresh, then specifying Mode "1680x1050" should result in the use of that display resolution.
Workaround is to add the modelines to the Monitor section of /etc/X11/xorg.conf. I copied the ModeLines from the /usr/share/xorg/extramodes file on an RHEL5.4 build. Another option in my case would be to remove the KVM and attach the monitor directly, then steal the ModeLine reported by the nouveau driver in /var/log/Xorg.0.log when it loads. This may not apply in other situations (different drivers/hardware, or some other reason for missing EDID).
This problem also prevents the selection of the correct display resolution using any of the GUI display tools.
Also note that if EDID is working, then the display resolution can be set without specifying the modeline. Clearly, my requirement is a special case where almost every user in my organization has multiple PC's and an analog KVM.
This request was evaluated by Red Hat Product Management for inclusion in a Red
Hat Enterprise Linux major release. Product Management has requested further
review of this request by Red Hat Engineering, for potential inclusion in a Red
Hat Enterprise Linux Major release. This request is not yet committed for
Actually, we should just alias the DMT mode list and xf86DefaultModes together. The latter is almost entirely anachronism now.
Red Hat Enterprise Linux 6.0 is now available and should resolve
the problem described in this bug report. This report is therefore being closed
with a resolution of CURRENTRELEASE. You may reopen this bug report if the
solution does not work for you.