From: Christoph Hellwig <hch@infradead.org>
To: James Bottomley <James.Bottomley@SteelEye.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
"David S. Miller" <davem@davemloft.net>,
matthew@wil.cx, SCSI Mailing List <linux-scsi@vger.kernel.org>,
Linux Kernel list <linux-kernel@vger.kernel.org>
Subject: Re: iomapping a big endian area
Date: Mon, 4 Apr 2005 15:16:16 +0100 [thread overview]
Message-ID: <20050404141616.GA10384@infradead.org> (raw)
In-Reply-To: <1112623143.5813.5.camel@mulgrave>
On Mon, Apr 04, 2005 at 08:59:03AM -0500, James Bottomley wrote:
> Well ... it's like this. Native means "pass through without swapping"
> and has an easy implementation on both BE and LE platforms. Logically
> io{read,write}{16,32}be would have to do byte swaps on LE platforms.
> Being lazy, I'm opposed to doing the work if there's no actual use for
> it, so can you provide an example of a BE bus (or device) used on a LE
> platform that would actually benefit from this abstraction?
The IOC4 device that provides IDE, serial ports and external interrupts
on Altix systems has a big endian register layour, and the PCI-X bridge
in those Altix systems can do the swapping if a special bit is set.
In older kernels that bit was set from the driver through a special API,
but it seems the firmware does that automatically now.
next prev parent reply other threads:[~2005-04-04 14:16 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-04-02 20:52 [PATCH] finally fix 53c700 to use the generic iomem infrastructure James Bottomley
2005-04-03 1:37 ` iomapping a big endian area Matthew Wilcox
2005-04-03 2:38 ` David S. Miller
2005-04-03 3:10 ` Matthew Wilcox
2005-04-03 3:40 ` James Bottomley
2005-04-03 4:08 ` David S. Miller
2005-04-03 4:27 ` James Bottomley
2005-04-04 7:50 ` Benjamin Herrenschmidt
2005-04-04 13:59 ` James Bottomley
2005-04-04 14:16 ` Christoph Hellwig [this message]
2005-04-04 14:25 ` James Bottomley
2005-04-07 23:57 ` Jesse Barnes
2005-04-04 14:22 ` Randy.Dunlap
2005-04-04 23:41 ` Benjamin Herrenschmidt
2005-04-04 23:43 ` Benjamin Herrenschmidt
2005-04-04 7:49 ` Benjamin Herrenschmidt
2005-04-05 7:42 ` Russell King
2005-04-05 14:05 ` James Bottomley
2005-04-05 18:55 ` Russell King
2005-04-05 20:02 ` Maciej W. Rozycki
2005-04-04 21:17 ` James Bottomley
2005-04-05 7:21 ` Christoph Hellwig
2005-04-05 14:05 ` James Bottomley
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