Keyboard mapping

[Jon Smirl]

On 5/22/05, Adam Jackson <ajax at nwnk.net> wrote:
> On Sunday 22 May 2005 17:29, Jon Smirl wrote:
> > My EGL driver also ignores the kernel VC mechanism. There is only one
> > VC in Linux which makes it incompatible with multiuser. In the future
> > something can be implemented that looks just like VCs but follows the
> > rules to make it compatible with Xgl.
> 
> You do not necessarily need a VC to run an X server.  You just need a
> framebuffer.  Look at the ruby patches, or bug #2216 (which I am admittedly
> tardy on delivering).

I know that VCs are not required to run the X server. The problem
comes from people who run consoles in some sessions and the X server
in another. On VT swap nasty things happen. Number one, the current X
server disables all VGA devices in the system. Disabling all VGA
devices is bad for the other users since they are using them and they
haven't swapped VTs.

The other problem with VT swap is that historically you are allowed to
do anything you want to the video card in another VT session. That
includes changing the engine mode and wiping VRAM. This plays havoc
with things like monitor hotplug - the interrupt may be enabled and
the other VT session replaces the driver. Or it may disable the
interupt and you miss the event.

My personal preference is to see in-kernel VTs eliminated and replaced
with a user mode scheme that looks just like them. A single device
driver (merged fbdev/DRI) would be loaded and control the state of the
video card. The user space VT implementation would then use this
single driver. A primitive in-kernel console would be maintained but
it would only be used for system emergencies, normal login would use
the user space console.

Taking the multiuser concept further you can conceive of a system with
two independent users, one logged into each head of a multihead
display. In this case it is obvious that the free-for-all system on VT
swap is not going to work. You just can't let one user do anything
they want to the video card without impacting the other.

-- 
Jon Smirl
jonsmirl at gmail.com