[PATCH 3/5] tty/vt: add con_bind and con_unbind functions

[Ville Syrjälä]

On Tue, Oct 08, 2013 at 06:12:15PM -0300, Paulo Zanoni wrote:
> 2013/10/1 Ville Syrjälä <ville.syrjala at linux.intel.com>:
> > On Thu, Sep 26, 2013 at 08:06:00PM -0300, Paulo Zanoni wrote:
> >> From: Paulo Zanoni <paulo.r.zanoni at intel.com>
> >>
> >> The consoles who need to do something when unbinding or binding can
> >> optionally implement these functions.
> >>
> >> The current problem I'm trying to solve is that when i915+fbcon is
> >> loaded on Haswell, if we disable the power well (to save power) the
> >> VGA interface gets completely disabled, so when we unbind fbcon we
> >> need to restore the VGA interface to allow vgacon to work.
> >
> > We don't need to make it work. No one else does, and in the general case
> > it's even impossible since on some hardware that would definitely
> > corrupt the state that the real driver is attempting to use. The only
> > case where it might be nice to restore vgacon is on i915 unload, but no
> > one else does that either AFAIK, so I would not waste any cycles on
> > attempting that.
> 
> I don't understand your point. Without patches 3-4-5, module_reload
> doesn't work at all if the power well is disabled: we need these
> patches to fix it. The plan is not to restore everything to make
> vgacon actually work, the plan is just to prevent it from breaking
> module_reload.

How does the power well vs. vgacon break module_reload?

BTW module_reload seems to be busted on ILK and IVB too currently.

-- 
Ville Syrjälä
Intel OTC