Why does fbdev_drv need a console?

Christoph Theis theis at gmx.at
Sat Apr 6 07:03:19 PDT 2013


I have a Raspberry Pi and want to use 2 monitors, each of them with its 
own X server. One monitor is attached to the HDMI output, the other is a 
USB monitor attached to a USB port. Starting only one X server 
everything is fine: I have X either on the HDMI or on the USB monitor. 
But when I start the second X server, regardless which one, the other 
monitor goes blank (black). It will gon on again when I stop the second 
X server.

After some debugging I found out that the function FBDevDriverFunc in 
fbdev.c (fbdev_drv) called with op == GET_REQUIRED_HW_INTERFACES sets 
*flags=0 and thus the function InitOutput in xf86Init.c will open a 
console which in turn will blank the screen. I changed the body of 
FBDevDriverFunc to set *flags=HW_SKIP_CONSOLE and everything seems to be 
fine now.

So my questions are: Why would we need a console at all?
And if a console may be required can it then be made optional?
Or is there any other way to open the console somewhere else? I tried to 
start the X server with vtXX arguments but with no success.

Best regards

Christoph Theis

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