Hi Chris! > > I have a question about "what if physical memory is fragmented"? > > The AGIPIOC_ALLOC call returns a 'physical' address. > > This implies that the ALLOC is a single contiguous chunk of physical > > memory. Right? > > > > However, I cant imagine that it is easy to guarantee 64 megs of contiguous > > physical RAM allocation. So something seems wrong with my assumption. > > AGP memory is not allocated contiguously (check the calls to agp_bridge. > agp_alloc_page in agp_allocate_memory). > > However, it does look like AGPIOC_ALLOCATE is broken. It only returns > the ->physical field of the resulting agp_memory structure. It doesn't > even look like this field is set for any chipsets other than the i810 > and i830.
That's because it's not necessary. The user can only get the physical
pointer if he/she does an ALLOC with type > 0 which is a chip specific ALLOC
and it is up to the driver to implement these types or not.
> Is /dev/agpgart even supposed to work on Linux? I don't think any
> programs use it, and the rest of the kernel used the backend interfaces
> directly. It's possible that the frontend has fallen out of sync with
> the back. Can anyone here confirm or refute this?
Of course it's used. It essential for some X drivers such as i8xx series
chips. There is nothing wrong with the frontend either.
--
Regards
Abraham
Those who educate children well are more to be honored than parents, for
these only gave life, those the art of living well.
-- Aristotle
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Abraham vd Merwe - 2d3D, Inc.
Device Driver Development, Outsourcing, Embedded Systems
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