[Debian-eeepc-devel] Video out toggling

Paul Menzel paulepanter at users.sourceforge.net
Wed Sep 10 06:57:22 UTC 2008

Dear Phil,

two questions.

Am Dienstag, den 09.09.2008, 22:42 +0100 schrieb Phil Endecott:
> Hi Everyone,
> I have been playing with Fn+F5 video out toggling on my '901.  I would 
> guess that most of this applies equally to the smaller Eees.  Assorted 
> observations follow:
> 1. If the external monitor is attached when X starts, it chooses a size 
> based on the DDC from the external monitor and the LCD just displays 
> the top left corner (I don't think there's a way to pan this, is 
> there?).  This was surprising; I have no idea how to fix it.
> 2. Attempting to toggle when the XDM login screen is displayed doesn't 
> work.  My guess is that DISPLAY and/or XAUTHORITY is not being set 
> correctly in this case.  This could presumably be fixed in the 
> scripts.  (Where do errors from e.g. the xrandr command in the 
> vga-toggle.sh script go to?)
> 3. The default script (well, the version that I have) sets the mode for 
> the external monitor to 640x480, so only the top left portion of the 
> screen is shown.  Changing it to 1024x600 in 
> /etc/default/eeepc-acpi-scripts fails because 1024x600 is not a mode 
> that my external monitor advertises in its DDC.  (In fact, I guess that 
> very few if any monitors would advertise this mode; it's not one of the 
> standard modes that needs only one bit of DDC data, and there's limited 
> space in the DDC ROM for advertising non-standard modes.)  However, I 
> would be very surprised if there are any monitors made this millennium 
> that would fail to display this mode if given it; at most you would 
> need to press the "auto" button.  And X already knows the timings for 
> it because it's supplying it to the panel, so all that you need to do is
>    xrandr --addmode VGA 1024x600
> before the existing "xrandr --output VGA --mode" and it will just 
> work.  A minor snag is that the current split between 
> /etc/acpi/actions/vga-toggle.sh and /etc/default/eeepci-acpi-scripts 
> doesn't suit this configuration.
> 4. 1024x600 renders no worse than 640x480 on my 1600x1200 external 
> monitor; however, the scaling that the monitor does does not look 
> great.  1024x768 looks much better after scaling because it's the same 
> scale factor in X and Y.  But 1024x768 is better than the LCD.

Could you elaborate on this last sentence please? I did not understand
it. Do you mean the internal monitor cannot handle 1024x768?

>   The 
> solution is to use a 1024x600 "letter box" mode where there are 600 
> active lines and 168 blank lines, so that the monitor thinks it's 
> 1024x768.  I got this to work with the following:
>    xrandr --newmode 1024x600LB 78.8 1024 1040 1136 1312 600 601 604 800
>    xrandr --addmode VGA 1024x600LB
>    xrandr --output VGA --mode 1024x768LB
> That works, though it puts all the blank lines at the top of the 
> image.  For some reason my monitor didn't like it when I tried to put 
> half the lines above and half below, but I may have mis-typed 
> something.  I'll have to get my scope out and try again.
> Presumably with some clever scripting you could cycle through all these 
> various possibilities.
> Still to do:
> - I would be interested to hear from anyone with a widescreen monitor 
> (e.g. 1440x900) who can try this.
> - Is there any way to use the native resolution of the external monitor 
> and to show a scaled-down version on the Eee?
> - I am very keen to get external monitor switching working for the 
> console.  Also I'd like to get a 1024x600 console, which I think needs 
> either a BIOS fix or some serious surgery in the intelfb driver.  If 
> anyone knows anything at all about this, _please_ get in touch!

Where did you find all this information. Manpages or can you share a
great website?


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