Your video card is probably too old.
vesafb works the following way : when the init code is still in real mode,
it uses the vesa bios functions to initialize the graphic mode and get
a framebuffer ; then it builds a data structure with all the needed
informations on this framebuffer and pass it to the protected-mode
kernel, where vesafb gets it and does it work.
All this happens in linux/arch/i386/boot/video.S
The ability to get a framebuffer with a bios call was introduced in
vesa 2.0. If your video card is too old, it will provide only vesa 1.2
(or earlier) that allows video mode switching but gives no framebuffer
(even if the card can provide such a thing). My S3 Trio 64 V+, bought in
1995, was vesa 1.2. In order to get a boot logo, I had to switch to a
S3 Virge brand new video card.
Note that, using a very reduced msdos (or freedos) installation, and
loadlin.exe, you can use vesafb with vesa 2.0 functions provided by
a msdos tsr program, thus giving this possibility with old hardware.
It might require some tweaking, for I do not know when the msdos memory
is erased by the linux kernel when using loadlin.
--Thomas Pornin
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