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List:       dri-devel
Subject:    Re: [Dri-devel] Re: Copying DMA buffers in Mach64
From:       Alan Cox <alan () lxorguk ! ukuu ! org ! uk>
Date:       2002-10-30 23:56:49
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On Wed, 2002-10-30 at 22:05, Jos=E9 Fonseca wrote:
> http://kernelnewbies.org/documents/copy_user/ . But although I do
> understand the assembly implementation and I actually plan to do an
> assembly optimized version myself, I would like to start with a plain C
> implementation that would be platform independent.

Thats always a good idea anyway. The Alpha and PPC people will be your
friends for that 8)

> But it doesn't seem I can get away of assembly due to the exception
> table. So the only way is to do it portably is to call __copy_user
> inside my routine for every read, or do you have any other suggestion
> you can give me?

You can do __get_user() and seperate verify_area at the start. or you
can grab the data in small chunks. The basic theory of processing data
while its in L1 cache isn't totally dependant on hand tuned asm loops
and grabbing in chunks will work fine too.



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