Question about 64-bit code safety

Dave Airlie airlied at
Tue Sep 6 23:49:29 PDT 2005

> If you're using a pointer as a nonce, don't you want to be sure that
> it's unique?  Do you ever need to convert the handle back into a
> pointer?

You know you could read the code and I think the mailing list history..

32-bits should be quite enough, its a handle, nothing else, the
pointer gets hashed and sent to userspace and when sent back it gets
unhashed and used.. in fact we don't have 32-bits, I think we actually
only have 28-bits as mmap knocks of the bottom few bits....

no matter its enough for the DRM, we create at the moment about 5
maps, so I'd hope we don't suddenly required 64-bits of map storage...

> In either case, you wouldn't want to drop the upper bits and lose
> precision.

Why wouldn't we? we designed it like that.. 3 people involved all
agreed this was a correct solution...


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