Bug 8062

Summary:	Blank console if vga=<vesa mode> and CONFIG_FB not set
Product:	Drivers	Reporter:	Bruno Prémont (bonbons)
Component:	Console/Framebuffers	Assignee:	Antonino Daplas (adaplas)
Status:	RESOLVED CODE_FIX
Severity:	normal	CC:	bunk
Priority:	P2
Hardware:	i386
OS:	Linux
Kernel Version:	2.6.20	Subsystem:
Regression:	---	Bisected commit-id:

Description Bruno Prémont 2007-02-22 13:42:47 UTC

Kernel having the following console/framebuffer config settings:

# Character devices
#
CONFIG_VT=y
CONFIG_VT_CONSOLE=y
CONFIG_HW_CONSOLE=y
CONFIG_VT_HW_CONSOLE_BINDING=y

# Graphics support
#
CONFIG_FIRMWARE_EDID=y
# CONFIG_FB is not set

# Console display driver support
#
CONFIG_VGA_CONSOLE=y
# CONFIG_VGACON_SOFT_SCROLLBACK is not set
CONFIG_VIDEO_SELECT=y
CONFIG_DUMMY_CONSOLE=y
# CONFIG_BACKLIGHT_LCD_SUPPORT is not set


When booting such a kernel with vga=normal commandline option the console 
displays correctly, but when setting vga=<vesa mode> the screen remains blank 
(though active) and console output never shows up.

I would expect that when the framebuffer is not compiled the kernel should 
ignore vesa modes and keep console in text mode in order to be able to display 
console output.


I can reproduce this issue on i386 hardware (tried on one Fujitsu Siemens 
Centrino Laptop and a HP Proliant G5 Server). I have not tried x86_64 though I 
assume it may also be affected by this same issue.
If this is of any use I may check x86_64 using the Proliant server as it has 
x86_64 capable Xeon CPUs. Possibly any i386 or x86_64 hardware with vga/vesa 
graphics adapter is affected.


System environment:
SuSE 10.2, Gentoo (gcc-4.1.1)

Comment 1 Antonino Daplas 2007-02-22 15:47:52 UTC

Yes, that's known behavior.  I believe this can be easily fixed, but I'm still
not too sure of the repercussions.

But you're probably correct, it's probably worthwhile to change this behavior.

Comment 2 Antonino Daplas 2007-03-05 07:38:29 UTC

Patch in 2.6.21-rc2-mm1.  If framebuffer is not enabled, or compiled as a
module, booting with VESA graphics mode will stop the boot and user will be
prompted to enter a valid text mode.

Comment 3 Bruno Prémont 2007-04-19 10:20:39 UTC

Thanks, works fine.

Looking forward to see it in mainline!