[ltp] Re: RFC: removal of video output switching from thinkpad-acpi

[Paul Fox]

alex wrote:
 > On Feb 20, 2008 10:40 AM, Paul Fox <pgf@foxharp.boston.ma.us> wrote:
 > > alex wrote:
 > >  > This is a hw/bios implementation limitation.  The same crtc can't
 > >  > drive both VGA and LVDS at the same time.
 > >
 > > and X doesn't suffer this limitation?  (forgive my ignorance, please)
 > 
 > No. the X driver knows how to fully program the hw.  The bios only has
 > limited space and it's just there to get an image on the screen when
 > you boot.  It's not really worth the time and expense to implement
 > support for multiple crtcs in the bios code just you you can toggle
 > outputs from the console especially considering most windows users
 > will never use text mode.

gotcha.  thanks.

 > >  >
 > >  > If you are using X, this is not a good idea.  stick to xrandr.
 > >
 > > but this doesn't work if you're not running X, right?  i suspect i
 > > have the same needs that elias does.  sometimes i work at the console,
 > > sometimes i work using X.  sometimes i work at an external monitor.
 ...
 > that's fine.  use randr in X and a script in the bios.  My point is
 > just that you don't want to use bios switching routines in X because
 > the bios will be touching the hardware behind X's back which will
 > result in a unknown state, which very well could hose your display or
 > hang your box.

gotcha, and thanks, again.

paul
=---------------------
 paul fox, pgf@foxharp.boston.ma.us (arlington, ma, where it's 25.5 degrees)