Re: [Linuxconsole-dev] EvStack - 2.3.x?

[Dominik K. <dom...@un...>]

On Sat, Mar 04, 2000 at 11:48:05PM -0500, James Simmons wrote:
...
> Thats me and Geert writing that code :) What is needed to deal with in the
> console system is keeping track of what VTs are active. Right now only one
> can be active (fg_console) :( 

IMO console and vc's are different. So let's agree on consistent terminology
right away:

   console = /dev/console    System console device, might be serial terminal
                             or even a teletype/line printer.

   virtual tty's = /dev/tty[0-9]+

                             Virtual tty's with VT102 terminal emulation.
                             Should be called vt's IMHO and we should use
                             something like ptmx/pts to create the devices
                             on demand (what do you think? And PLEASE nobody
                             mention devfs in my presence!)

What i want to do is to separate the two. Keep the console small and clean.
If you are running linux on a PC104 embedded system with serial console,
then there is no need for VC's. Fortunately we can do this already, but the
code is still mixed right now.

Some thing we might want to look into is a network-base console (using UDP
unicast/multicast/broadcast or whatever one uses for these things).

> Vojtechs work :) Screw the /dev/mouse crap. We have /dev/event. It
> basically works like /dev/shmiq on IRIX. Its a event queue. A app opens it
> and reads the event packets that arrive. It works for ANY input device :)
> Raw access to the input hardware.

The problem i see here is that this becomes too opaque for the casual user.
Might be clean and nice from a design standpoint, but will certainly irritate
some folks.

> We have to deal with SMP multihead systems. You could have different
> processes running on different CPUs using different heads. As you can see
> we need locking to ensure data structures are altered by the wrong VT.
> Next problem I bet you didn't think about. Printk being called inside a
> bottom handler can also cause nasty race conditions. This was something
> Mares notices while working with Vojtech. 

Ouch!  Your pulling my leg, do you?  We don't even have support for partioning
linux systems and you want to build a console framework for this?  But with
the /390 port and thingies like E10k around this is something we have to
think about.  I'll ask a friend of mine about his input: he's the local expert
for the Convex/HP supercomputers... I think they use a seperate HP workstation
as console device.

> > PS: I have put my console-patch up for grabs at:
> > 
> >     http://www-klinik.uni-mainz.de/staff/kubla/Linux/

It's the same i posted to linux-kernel last week when this discussion
started.  Unfortunately i have (again!) no network when running >2.3.36
kernels and my laptop just forgot about some essential keys (i wonder
what the DELL support will say about this when i call in tomorrow!) so i
am somewhat hobbled at the moment.

Yours,
  Dominik
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