Bug 8062

Summary: Blank console if vga=<vesa mode> and CONFIG_FB not set
Product: Drivers Reporter: Bruno Prémont (bonbons)
Component: Console/FramebuffersAssignee: 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!