Re: Since chvt works, the problem must be the keymap

[cga2000 <cga2000@optonline.net>]

On Sun, Apr 29, 2007 at 02:51:13PM EDT, Florian Kulzer wrote:
> On Sun, Apr 29, 2007 at 14:10:14 -0400, cga2000 wrote:
> > On Sun, Apr 29, 2007 at 12:10:22PM EDT, Florian Kulzer wrote:
> 
> [...]
> 
> > > It would be interesting to see which keycodes and keysyms are reported
> > > if you run "xev", press (and hold) both CTRL and ALT, and then press F1,
> > > F2, etc. Does xev really display the keycodes for the Fn keys and the
> > > keysyms "XF86_Switch_VT_n"? Are the hexadecimal keysym values the same
> > > as the ones that you get with "grep VT /usr/share/X11/XKeysymDB"?
> > 
> > Another way of looking at it is that _unless I am totally misunderstand
> > how these things work_ .. the CTRL+Alt.. sequence invokes "X server"
> > code and the "disconnection" from the VT as Andrew nicely put it, is
> > eventually processed (in part at least) by your card's driver .. whereas
> > with "chvt" it is code that lives in the kernel that is invoked.
> > 
> > Hence a buggy video card driver could cause CTRL+Alt.. to fail on a
> > system where chvt works..  Regardless of keyboard mapping ..
> > 
> > The "logic" :-) behind this embarrassing guesswork of mine is that I
> > have experienced this kind of problem with embedded chips (together with
> > a slew of other issues) in cases where the driver was clearly described
> > as immature in the (then) xfree86 doc.
> > 
> > That's why I suggested .. possibly in another recent thread on a similar
> > subject
> 
> It probably was the same thread. One of the morons from debianhelp.org
> has gratuitously changed the subject line in the meantime, which does
> not really contribute to making things any clearer.
> 
> >         .. was it an nvidia card then? .. switching to the VESA driver
> > just to see if it makes any difference.
> > 
> > Naturally, checking whether you are running the latest version of the
> > driver and taking a peek at it's change log is matter or course.
> > 
> > Let me know if this makes sense.
> 
> I think we certainly cannot rule out anything at the moment. I seem to
> recall, though, that some people who reported the VT switching problem
> in the past did try the vesa driver and found that it did not help. 

Not even sure it did in my case .. unfortunately this was on machines I
no longer own so I can't just run a quick test myself.  My very vague
hunch is that this may turn out to be something more involved than a
problem with keyboard mapping.  And then again it might be. It's
difficult to tell without actually having the machine to fiddle with.

> My feeling is that a problem with the graphics driver would either
> lead to a lock-up of the system, a crash of X, or at least to error
> messages in the Xorg log. I don't remember if we ever suggested that
> people check the log.  

> It is certainly annoying that this is a persistent problem for a small
> percentage of users and that we cannot figure out what causes it.

Maybe someone closer to X development might shed some light on how this
works.  I don't remember going to a specialized list or newsgroup when I
ran into a similar problem myself. To make things more complicated, the
machines shared a kvm with a couple of others and since I mostly ssh'd
to them, I have a feeling I just decided this wasn't worth the trouble.

Thanks,
cga