On Tuesday 29 April 2008 17:29:24 Jerome Glisse wrote:
> For console we had the idea of building a full userspace console things
> instead of having this whole things in the kernel. Which would mean to
> write some userspace program using the modesetting API and providing
> the console. I believe there is several advantages (i talk about drawbacks
> latter) for instance you can do a fency console, or have multiple
> console at the same time by dividing screen, or have efficient multi-seat
> console with nice screen & input association. Well many things worth
> having for the XXI century where car flies and robots wash the house and
> do the laundry.

I'm not sure I quite follow on the user-space console thing. Do you mean that 
tty0-5 get removed & replaced with ptys? In fact the only real ttys left are 
serial ports? A daemon process is created by init which opens the drm & input 
devices, creates 6 or so ptys for each vt. It then implements a framebuffer 
vt102 or something and lets init attach gettys or whatever to the slave ptys.
The daemon watches for Alt+Fx etc. and switches framebuffers & which pty
it sends keyboard input to. Have I understood correctly? It seems like vt's
become a completely user-space thing. This is great for console applications,
but what about graphics applications? Is that where this multi-master thing
comes in to play?

> Main drawback i see, is for rescue case, ie we likely need to keep a
> minimal console in kernel as in rescue we can't rely on userspace to
> be their or operational. Their is likely others drawback but none of
> importance come to my mind.

There's also the boot splash before the kernel brings up userspace (although
I think userspace is brought up pretty quickly with initramfs). There's also
all the fbdev drivers, although I guess the user-space console could also 
support the fbdev interface too.

> 
> Anyway i believe such things need to be discused on lkml but as the API
> and things like multi-master, DRM2, ... are not yet worked out i believe
> its a bit too early to bring this topic on lkml (given that this might
> proove to lead to some nice flamewar :() Still you might be interested
> in writing a proof of concept user space console. Adapting it to
> API change won't be that hard.

Yeah, you seem to be talking about some fairly major changes to Linux. 
Where is all this discussion going on? Is there a DRI2 mailing list 
somewhere? I'd quite like to follow what's being planned.

As for userspace console, it seems fairly strait forward. I guess the easiest
thing would be to grab an existing terminal emulator which renders to a
framebuffer & adapt it? Either fbcon or something like rxvt/similar.


Thanks for the info!


Cheers,

Tom

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