From: Ion Badulescu <ionut@badula.org>
Date: Wed, 19 Feb 2003 17:41:39 -0500 (EST)
> Nearly all cards today are 64-bit DMA address descriptors only.
> So if anything, this new ifdef will get less and less used over
> time.
Not true. Even if the only descriptors available are 64-bit, there is no
reason why I should have to care about the upper 32 bits when I know that
my dma_addr_t will always be 32-bit, at compile time. I can simply
memset(0) the entire descriptor and initialize only the bottom 32 bits.
Yes true, storing the two consequetive 32-bit values is better
for store buffer compression of the cpu. Using memset is much
more inefficient because you push the full set of data once
then you push non-compressible stores to the same data through
the cpu.
I'm not talking out of my ass, I've measured this.
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