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Re: [PATCH] I/O helpers rework

To: Herbert Valerio Riedel <hvr@inso.tuwien.ac.at>
Subject: Re: [PATCH] I/O helpers rework
From: "Maciej W. Rozycki" <macro@mips.com>
Date: Mon, 10 Jan 2005 13:05:51 +0000 (GMT)
Cc: Ralf Baechle <ralf@linux-mips.org>, linux-mips@linux-mips.org, "Maciej W. Rozycki" <macro@linux-mips.org>
In-reply-to: <1105029224.4361.21.camel@xterm.intra>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <Pine.LNX.4.61.0412151936460.14855@perivale.mips.com> <1105029224.4361.21.camel@xterm.intra>
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On Thu, 6 Jan 2005, Herbert Valerio Riedel wrote:

> jfyi, this change broke mtd and au1xxx-usb on big endian au1xxx systems,
> as the _raw calls do suddenly byteswapping :-(
> 
> was this intended?

 It was.  Generic code elsewhere expects it and the MIPS implementation 
used to be broken because of that.  Note these functions are intended for 
PCI/EISA/ISA accesses only and these buses are little-endian by 
definition.  More specifically __raw_ calls are mainly for PIO copying 
to/from memory over these buses when you want to keep byte ordering the 
same as it would be for a DMA transfer.

 If you have a driver that handles a non-PCI/EISA/ISA device you may and 
probably should use bus_ calls to get a non-swapped access.

  Maciej

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