[ltp] x41 monitor selection

[Alex Deucher]

On 1/30/07, Paul Fox <pgf@foxharp.boston.ma.us> wrote:
> alex wrote:
>  > On 1/30/07, Paul Fox <pgf@foxharp.boston.ma.us> wrote:
>  > > as a reminder, my problem is that using the fn-key to switch
>  > > monitors on my X41 will give me either the external or the
>  > > built-in display, but not both.  this is even though both
>  > > displays work fine together when the X server first starts (or is
>  > > restarted).
>  ...
>  >
>  > Unfortunately, you are going to be out of luck.  The problem is you
>  > have two things writing to the video hardware without each other's
>  > knowledge.  When you press the fn-key video output toggle, the video
>  > bios arbitrarily writes whatever it wants to do to the video hardware.
>
> so am i to take it that this mode of video switching (with the fn-key)
> doesn't work for anyone on their thinkpad?  if that's the case, i'm
> surprised (and disappointed!) that no one else has spoken up.  :-)
>

Well, not exactly. It depends on two factors:

1.  the video hardware.  the intel hardware has certain limitations
2. how you want to toggle the outputs.  if you want to switch from
single head on the panel to single head on the crt port or to clone
mode (other chips can drive multiple outputs with a single crtc), then
there won't be a problem in many cases as the mode programmed by the
bios is similar enough to the mode programmed by the xorg driver, that
it doesn't cause any problems.

>  >  This writes all over the values the xorg driver has written.  After
>  > you've pressed  the fn-key combo a few times the hardware state is
>  > completely hosed up.  You may be able to get it back by switching to
>
> well, it's not completely hosed -- the two single-display modes continue
> working fine.  it's only the dual-display mode that doesn't work.
>

well, hosed is relative... :)

> i was sort of wondering if i'm not seeing a variant of this bug:
>     https://bugs.freedesktop.org/show_bug.cgi?id=5817
>

they may be related in that they are probably both related to a funcky
video bios.

Alex

> i think i understand the rest of what you said, and it makes sense...
>
> paul
> =---------------------
>  paul fox, pgf@foxharp.boston.ma.us (arlington, ma, where it's 24.3 degrees)