Messages in this thread | | | Date | Mon, 30 Apr 2007 13:58:56 +0100 | From | James Pearson <> | Subject | Re: X display shift with disabled console blanking |
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Antonino A. Daplas wrote: > On Fri, 2007-04-27 at 18:08 +0100, James Pearson wrote: > >>I have a problem whereby the X display 'shifts' to left when anything >>writes to /dev/console - where console screen blanking has been disabled >>i.e. doing something like: >> >>boot to run level 3 >> >>If not root, then make sure /dev/console is writeable >> >>login and type: >> >>setterm -blank 0 >> >>start X >> >>type into an xterm: >> >>echo "some random text" > /dev/console >>(may have to repeat the echo above a few times) >> >>... and the whole X display jumps (and wraps) to the left >> >>I'm using a RHEL4 based distro with a vanilla 2.6.21 x86_64 kernel >>(although I've seen the problem with various x86_64 and i686 2.6.X kernels). >> >>I've seen this problem on a number of different nVidia cards - using >>the vesa driver (same problem occurs with nVidia's binary driver). I >>haven't tried using other makes of graphics cards. >> >> >>OK, this may be a strange combination of disabling the text console >>blanking and running X, but something isn't right somewhere ... > > > Yep, it's strange because I can't reproduce this. And the console write > should not succeed if the current console is in KD_GRAPHICS mode, which > is done by X (unless your version is different).
I've just installed a vanilla CentOS 4.4 on an i686 SMP machine - with an nVidia Quadro4 980 XGL card.
By default, this sets up X using the 'nv' driver (using RedHat's xorg-x11-6.8.2-1.EL.13.37).
If I follow my 'recipe' above, then the screen shifts - note: it looks like you have to write several lines of text to /dev/console (at least 30) to trigger the problem (e.g. run the echo to /dev/console in a loop) - also, I've found that switching to the console and back to X (Ctrl-Alt-F1 then Ctrl-Alt-F7) while this echo loop is running can force the shift to start ...
This is with the RedHat based 2.6.9-42.ELsmp kernel - but I also get the problem with a vanilla 2.6.21 kernel.
>>Any ideas? > > > I don't. But, what is your current console? Is it VGA, or framebuffer? > Can you try doing this again in both VGA and vesafb?
I'm not sure what the current console is - whatever is the default with RHEL4/CentOS4 - how do I select a different type of console?
> And this does not happen if there is no previous setterm -blank 0 > command?
It doesn't happen if there is no previous 'setterm -blank 0' - so, arguably, this is the 'fix' ...
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