> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED]]On Behalf Of Ian Romanick
> Sent: Friday, January 24, 2003 12:29 PM
> To: DRI developer's list
> Subject: [Dri-devel] 64-bit kernel, 32-bit user. Possible? Painful?
>
>
> So, I was thinking about some CPUs that are about to hit the market and
> how they will interact with DRI. The main issue that I came across was
> with x86-64. When x86-64 systems roll of the line, they'll
> (eventually?) have 64-bit kernel support and (for legacy apps) 32-bit
> user-mode support.
>
> My question is, what are the gottchas of having the DRM run in a 64-bit
> kernel and the rest of the driver run in either a 32-bit application or
> a 64-bit application? Will it even matter? If it will matter, is there
> anything we can start doing now to soften the blow?
>
We might have a problem here, basically we use the kernel address of
certain structures as a convient method of passing keys around. Well, when
a 64-bit kernel is running and we have 32-bit usermode we aren't going to be
able to shove 64-bit pointers into 32-bit ulongs. We probably need to fixup
all the kernel code so that it doesn't use the addresses as keys, but
something else. We could probably do it in such a way though that we don't
impact any of the userland code. This is probably something we should have
done a long time ago, when we saw this very same issue on the sparc. If we
want this to work we need to do the kernel development to make it right.
Otherwise it just won't work correctly.
Also I dunno how 32-bit usermode / 64-bit kernel will work when it comes to
ioctl's. I would imagine it is probably not transparent, especially since
most of the structures contain boatloads of unsigned longs instead of fixed
sized things. The ioctl code in general will probably need to be worked on
besides our internal usage of pointers as handles for userspace.
-Jeff
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