Date: Thu, 10 Mar 2005 01:45:25 +0100
From: Francois Romieu <romieu@fr.zoreil.com>
To: Andi Kleen <ak@muc.de>
Cc: Stephen Hemminger <shemminger@osdl.org>, netdev@oss.sgi.com
Subject: Re: [PATCH 1/5] r8169: auto detect 32-bit slot
Message-ID: <20050310004525.GA12735@electric-eye.fr.zoreil.com>
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Andi Kleen <ak@muc.de> :
[...]
> The concept of "64bit systems" is useless here anyways. Even on a 32bit
> system with highmem like i386 you can get >32bit addresses to deal
> with. One usecase for that would be sendfile() out of user space.
> This is widely used these days.

The combination "32 bit system with weird addressing mode + r8169 adapter"
has accounted for 0 bug/success report so far and I do not know a single
tester for it anyway. Whence my narrow-minded view of the issue :o)

[...]
> Again are you sure it depends on 64bit slots? Normally 64bit slots
> only offer more bandwidth, but the address protocol is the same
> as 32bit and both support DAC in the same way.

I do not know. The 8169 includes a register which tells (various things +)
the bus width. Without further documentation, I do not see how the relevance
of this register can be established/discarded if the aforementioned
test-cases are not experienced.

[...]
> You really should forget about amd64 or not, all that counts is
> sizeof(dma_addr_t) 

(assuming the on-board 8169 is wired correctly, be it on-board or not, yes)

--
Ueimor