Improving VT switching with KMS

Michel Dänzer michel at
Thu Feb 25 00:49:09 PST 2010

On Wed, 2010-02-24 at 15:54 -0500, Ari Entlich wrote:
> When using KMS, is it safe for the {Enter,Leave}VT callbacks to not be
> called exactly prior to entering/leaving a VT? Obviously if the
> drivers didn't register these callbacks then it would be pretty easy
> to tell, but all three of the drivers listed above DO register these
> callbacks, whether in the KMS context or otherwise. So since I assume
> that these callbacks do have some purpose, I guess my question is
> really: what sort of effect would not executing them have? Would it
> cause text VTs to not work?


> Would it cause subsequent usage of X to not work?

At least in the case of the radeon driver, yes. The crucial parts are
the drmSet/DropMaster calls. This also means that when switching from
one X server VT to another, the LeaveVT hook of the former needs to be
called before the EnterVT hook of the latter, or things will break.

> Also, I'm curious if there's actually really any interest in this
> change. I don't know if it's just that I've been asking at the wrong
> times or what, but responses to my queries about this stuff on the irc
> channel seem to be a bit apathetic. Is this not something people
> want/care about?

It's IRC. :)

Earthling Michel Dänzer           |      
Libre software enthusiast         |          Debian, X and DRI developer

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