[Patch] Hashed map lookup.

[<th...@tu...>]

Hi, All.

I'd like to bring in the hashed map lookup from the drm-ttm-branch to 
CVS. It changes the drmmap() map lookup from a linked list search to a 
hash lookup.

This means that the user_token that identifies the map in user space 
becomes an arbitrary hash key in the range 0x10000000 to 0x90000000 with 
page-size increments.

Some 2D and 3D drivers (at least the SiS 3D driver) may still assume 
that the user_token is equivalent to the physical address of the area to 
be mapped. Something that will fail in a 64-bit environment, and that 
will fail catastrophically with the hashed lookup. The current DRM 
contains a workaround that maps 64-bit addresses to a certain 32-bit 
region to make those drivers work in 32bit mode, but sooner or later 
that workaround should go away, and the drivers be properly updated.

While this makes little performance impact now, when we add the TTM 
stuff, the number of maps may be very large so a hashed lookup is needed.

If anybody is very eager to keep the workaround, please speak up. For 
those drivers needing a fix, the DRM major needs to be bumped.

/Thomas