copy_from_user in drivers/video/fbmem.c

Geert Uytterhoeven geert at
Fri Jun 16 21:14:07 EST 2000

On Fri, 16 Jun 2000, Adrian Cox wrote:
> I've just ported the chips driver in 2.2 to the 69030 (now Asiliant, was
> Intel, was C&T). I've found that writing to the frame buffer device
> fails, because the underlying method in fbmem.c uses copy_from_user(),
> and on PowerPC copy_from_user() cannot copy into uncached space.
> Which do people think is wrong:
> Is copy_from_user() on PPC wrong, because it can't write to uncached
> space.
> Is fbmem.c wrong, because it tries to use copy_from_user() to memory
> mapped IO?

Congratulations! You found a bug in fbmem.c! Fbmem.c should not use direct
memory accesses to access the frame buffer, but must use fb_writel() and
friends instead.



Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds

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