I have stated "video=1920x1200-24@60" on my kernel command line. Instead it initializes a 80x25 text console with a low resolution of sth. like 640x480 or so. The video kernel command line is said to be the future replacement of vga= modes by the Xorg development team (vga= is said to be no more compatible with Xorg`s video mode initialization). Is it already implemented? If yes a fallback to a similar Vesa graphics mode with Vesa safe/restore mode on vt-switch may be an additional opportunity. occurs with and without kernel modesetting.
With radeon rv380 and a P275 Trinitron CRT, video=1024x768 on cmdline instead of vga=0xwhatever or vga=7whatever works for me with default modesetting state and Kulow/openSUSE kernel-desktop-2.6.37.2-3 and GA kernel-default-2.6.37.1-1.2 to produce same result on tty[1-6] as vga=791/vga=0x305/vga=0x317/vga=0x318 did before KMS implementation.
As far as I have tested it on my machine the radeon module needs to be loaded with KMS enabled (no radeon.modeset=0 parameter) to get the video kernel-cmdline option interpreted (/proc/cmdline). If you f.i. need to use uvesafb instead give the following option: uvesafb.mode_option=1600x1200-24@60 (1920x1200 is no Vesa mode). The same parameters can be given on modeprobe leaving the module name (radeon., uvesafb.) out (/usr/src/linux-ver/Documentation/fb).
This is not a bug, video= command line is only interpreted with kernel modesetting enabled. We don't support anymore non kernel modesetting case for radeon.