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Date: Thu, 23 Mar 2006 09:54:19 -0800
From: David Hawkins <dwh@ovro.caltech.edu>
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To: Mark Chambers <markc@mail.com>
Subject: Re: Memory mapping PCI memory region to user space
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> 
> PCI is actually endian-agnostic, so we're really 'fixing' the 
> Freescale PCI implementation with endian swapping.
> 

Hi Mark,

Its not agnostic, its little-endian.

The configuration space layout of parameters larger than a
byte are defined in little endian format.

The wiring on the PCI bus is little-endian, and 32-bit
quantities on the bus are represented by a logic analyzer
in little endian format.

But once you start talking about BAR regions, then yeah,
they're your bytes, do with them what you will. My hardware
uses a little-endian TI DSP, and an x86 host, so I
had been using compatible machines.

But the PLX PCI-9054 PCI chipset exposes BAR[0] and BAR[1]
as control registers that are little-endian format.

Conversely, we also use some Janz CAN cards, and their
messaging protocol over PCI uses big-endian format
structures in their protocol.

Dave