[PATCH] neofb: take existing display configuration as default

On a Dell Latitude CPi-A I noticed a strangeness wrt. the handling of an
external monitor by the neomagic framebuffer driver, namely when the laptop is
docked in a C/Dock II with the lid shut.

A cold boot would result in the BIOS configuring the video chip to use the
"external monitor only" mode, yet neofb would default to "internal LCD only".
An attempt for a quick fix by using the Fn-F8 keystroke to toggle the display
combination modes resulted in a reproductible hard lock, powering down being
the only solution.

The attached patch makes neofb probe the register for the current display
mode, using that value as a default if nothing was specified as kernel/module
parameter.

Signed-off-by: Antonino Daplas <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/video/neofb.c

···
 	/* If the user did not specify any display devices, then... */
 	if (par->PanelDispCntlReg1 == 0x00) {
 		/* Default to internal (i.e., LCD) only. */
-		par->PanelDispCntlReg1 |= 0x02;
+		par->PanelDispCntlReg1 = vga_rgfx(NULL, 0x20) & 0x03;
 	}
 
 	/* If we are using a fixed mode, then tell the chip we are. */