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SubjectRe: how to get virtual address from dma address
   From: Paul Mackerras <>
Date: Sat, 6 Oct 2001 18:06:23 +1000 (EST)

The argument for supplying this functionality in the PCI DMA code
would be that if it was done there it could be done once, and in a
sophisticated and efficient (and SMP-safe :) fashion, rather than
ad-hoc in each driver.

The argument against it is that if you provide such an easy way out,
people will just blindly transform bus_to_virt/virt_to_bus without
considering more straightforward methods when they exist.

I can not even count on one hand how many people I've helped
converting, who wanted a bus_to_virt() and when I showed them
how to do it with information the device provided already they
said "oh wow, I never would have thought of that". That process
won't happen as often with the suggested feature.

I am adamently against generic infrastructure to do this. Yes, it's
social engineering, tough cookies... it's social engineering that I
know is working :-)

Franks a lot,
David S. Miller
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