Re: sbusfb changes are wrong

From: Jakub Jelinek (
Date: Mon May 08 2000 - 10:05:07 EST

> Its not the framebuffer memory itself. Can I not write a userland app that
> opens /dev/fb and set the video mode to somthing else. Most low end pci
> cards have two apertures. One for big endian and another for little endian.
> In 8 bit mode the card will most like use the little endian aperture. So
> if you have the X server open /dev/fb and sets the mode via
> data to mmap the framebuffer. Then I use my own fbdev program. It calls
> FBIOPUT_VSCREENINFO to set it to a 16 bpp mode. This means the aperture
> has changed its address this fix->smem_start is invalid. Thus the X
> server will be writing to the wrong memory region.

Does not happen on any of the sbusfb driven cards, in fact PUT_VSCREENINFO
does not work there either.
You just have one chunk of physical memory for smart 32bit aperture, other
chunk of physical memory for dumb 32bit aperture, one for dumb 8bit red
aperture etc. and all these can be mmaped separately.


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