From: Sengan Baring-Gould <sengan@seqnet.net>
  To  : ggi-develop@eskimo.com
  Date: Tue, 25 Aug 1998 21:47:21 -0600

Re: UMA problem

Sengan Baring-Gould wrote:

> When running xf68_dev I noticed that it appeared
> to be writing into the compression buffer which is
> stored after the uncompressed frame buffer on the
> MediaGX... which of course screws things up nicely.
>
> In general games might want to store data in the space
> between the end of the used screen memory and
> fb_fix_screeninfo.smem_start+smem_len... which will
> cause badness on the MediaGX.
>
> So I need to be able to tell the fb device that the
> framebuffer just changed size... or at least prevent
> the memmapping to take over the whole memory
> space.
>
> In general this problem should occur with all devices
> using a unified memory architecture, so I'm not quite
> sure why fbcon does not allow it (the old amiga had UMA
> and screens of varying sizes for instance)

Ok it looks like I need the fb_mmap entry to be declared in
static struct fb_ops kgifb_ops. Is this a dynamic thing I can
override in my init? (might be a good idea if possible for fb.c
in the kernel)

Sengan