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Date: Mon, 6 Dec 2004 08:12:58 +1100
From: Paul Mackerras <paulus@samba.org>
To: Linh Dang <dang.linh@gmail.com>
Cc: Linux Kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH][PPC32[NEWBIE] enhancement to virt_to_bus/bus_to_virt (try 2)
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Linh Dang writes:

> I wrote a DMA engine (to used by other drivers) that (would like to) accept
> all kind of buffers as input (vmalloced, dual-access shared RAM mapped
> by BATs, etc). The DMA engine has to decode the virtual address of the
> input buffer to (possibly multiple) physical  address(es). virt_to_phys()
> has the right name for the job except it only works for the kernel virtual
> addresses initially mapped at KERNELBASE

Have you read Documentation/DMA-API.txt?  It explains the official
kernel API for DMA, and drivers should use it in order to be portable
to more than just one architecture.

If you want to create a competing DMA API, you'll have to show us at
least one driver that really needs your new API.

Also, please don't change the existing virt_to_*/*_to_virt functions.
Instead define your own functions (with different names) in the same
source file as your other new code.

Paul.