Re: [PATCH 5/5] VT binding: Add new doc file describing the feature

Jon Smirl wrote:

On 6/10/06, Antonino A. Daplas [off-list ref] wrote:

quoted

quoted

I see now that you can have tty0-7 assigned to a different console
driver than tty8-63.
Why do I want to do this?

Multi-head.  I can have vgacon on the primary card for tty0-7,
fbcon on the secondary card for tty8-16.

That's what I thought, I couldn't see any other reason. The kernel
doesn't support input from multiple users so multihead can only be
used by a single user.

Does anyone use single user multihead on current systems? The kernel
doesn't have code in it to initialize secondary VGA cards. What modern
non-VGA hardware does this work on?

matroxfb supports multihead and fbcon already has this feature for a
long time, ie you can bind /dev/fb0 to tty0-3 and /dev/fb1 to tty4-6.
And there are definite users because I happen to break this feature once
and I got rained with complaints :-)

If this feature doesn't work on current hardware, could it be dropped?
It would make binding to the vt system much simpler if only one driver
could be bound at a time. Anything we do to make that system simpler
would benefit everyone.

You can't drop something that's already in the kernel and has users, well,
the binding part at least. What we don't currently have is the fine-grained
control and because of the reason's you mentioned, I said that it's for the
future.

(Note1: fbcon already has support to selectively bind/unbind drivers
to specific tty's, using the con2fbmap utility.)

So what we have is control for wholescale binding and unbinding of
drivers, which essentially results in only 1 driver loaded at one time.

(Note2: fbcon already has an option to determine what range of vc's to
control, as a kernel boot parameter, so we can't just drop something 
that's already supported by one driver at least.  Though I know of no one,
including myself, who uses this feature.)

At some future point I would like to explore pushing the VT system out
to user space where it becomes much easier to make it multi-user and
multi-head. If you do that, something like a single user, in-kernel
system management console makes more sense.

Yes.

Tony