linux-kernel - Re: [PATCH] drivers/block/xsysace - replace in(out)_8/in(out)_be16/in(out)

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Date:	Fri, 08 Feb 2013 08:06:09 +1100
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Alexey Brodkin <Alexey.Brodkin@...opsys.com>
Cc:	Grant Likely <grant.likely@...retlab.ca>,
	Michal Simek <monstr@...str.eu>, Arnd Bergmann <arnd@...db.de>,
	Vineet Gupta <Vineet.Gupta1@...opsys.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	dahinds@...rs.sourceforge.net
Subject: Re: [PATCH] drivers/block/xsysace - replace
 in(out)_8/in(out)_be16/in(out)_le16 with generic iowrite(read)8/16(be)

On Thu, 2013-02-07 at 19:12 +0400, Alexey Brodkin wrote:
> not sure about items for "ace_datain/out_be16" - what about _rep
> options here?

Well, you have a backward wiring of an LE device so you can't use the
_rep variants, unless you ping pong, so you either use a loop of
ioread/write16 (le) and bite the bullet on extra barriers, or use _rep &
bounce buffer for a separate swap pass.

Point is, the backward wiring will require byteswap on both BE and LE
hosts for data (which is why it's so stupid).

Cheers,
Ben.



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