Ho trovato la risposta: baco/caratteristica di X:
http://bugs.freedesktop.org/show_bug.cgi?id=14611
La patch applicata funziona, e fa avviare X anche senza display collegati fisicamente. E' indispensabile, oltre alla patch, l'opzione
codice:
Section "Monitor"
### Comment all HorizSync and VertSync values to use DDC:
Identifier "Monitor0"
VendorName "Panasonic"
ModelName "TH-50PH11"
HorizSync 15.63 - 85.94
VertRefresh 50.0 - 85.06
Option "Enable" "true"
Modeline "1280x1024_75.00" 138.54 1280 1368 1504 1728 1024 1025 1028 1069 -HSync +Vsync
.
.
.
.
.
Modeline "1024x768_50.00" 51.89 1024 1064 1168 1312 768 769 772 791 -HSync +Vsync
EndSection
Per completezza, riporto anche la patch
codice:
diff --git a/hw/xfree86/modes/xf86Crtc.c b/hw/xfree86/modes/xf86Crtc.c
index 8c2b247..771523e 100644
--- a/hw/xfree86/modes/xf86Crtc.c
+++ b/hw/xfree86/modes/xf86Crtc.c
@@ -1342,7 +1342,8 @@ xf86ProbeOutputModes (ScrnInfoPtr scrn, int maxX, int
maxY)
*/
output->status = (*output->funcs->detect)(output);
- if (output->status == XF86OutputStatusDisconnected)
+ if (output->status == XF86OutputStatusDisconnected &&
+ !xf86ReturnOptValBool(output->options, OPTION_ENABLE, FALSE))
{
xf86OutputSetEDID (output, NULL);
continue;