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Date: Mon, 23 Jan 2012 15:04:27 -0800
From: "H. Peter Anvin" <hpa@linux.intel.com>
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To: Linus Torvalds <torvalds@linux-foundation.org>
CC: Hitoshi Mitake <h.mitake@gmail.com>, Ingo Molnar <mingo@elte.hu>,
        Matthew Wilcox <matthew.r.wilcox@intel.com>,
        Roland Dreier <roland@purestorage.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        James Bottomley <James.Bottomley@parallels.com>,
        linux-kernel@vger.kernel.org, linux-nvme@infradead.org
Subject: Re: [PATCH] NVMe: Fix compilation on architecturs without readq/writeq
References: <1327021265-22184-1-git-send-email-matthew.r.wilcox@intel.com> <CA+55aFwmDbDm5+12Nc0wnu7J8dsOKW0tCd_tVf-3pwQOq9MF3w@mail.gmail.com> <20120121082857.GC32134@elte.hu> <CAMO-S2hq0jGeUdAzMizDOhYJvPSQ=8+HVTUVqzsBOJotxOWrUg@mail.gmail.com> <20120121165830.GA9216@elte.hu> <CAMO-S2iegkRWGcnDt0SZqJT3Y3JHQZcHfMY=THKMN7n4Ae0Fyw@mail.gmail.com> <CA+55aFz=KcR5ji3TBHyfAYxFg8PCjXbdLOWf7aXULYHW4pp2kg@mail.gmail.com>
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On 01/23/2012 08:57 AM, Linus Torvalds wrote:
> On Mon, Jan 23, 2012 at 8:05 AM, Hitoshi Mitake<h.mitake@gmail.com>  wrote:
>>
>> I wrote the patch which adds the new file include/asm-generic/io-nonatomic.h.
>> io-nonatomic.h provides non-atomic version readq()/writeq().
>
> I do wonder if we should do "little-endian" and "big-endian" variations?
>
> Quoting Willy:
>
>    "For this particular hardware, it's defined to work if you read the
> low order bits first"
>
> so I think we need make that explicit, and make two include files:
>
>     include/asm-generic/io-64b-lo-hi.h
>     include/asm-generic/io-64b-hi-lo.h
>
> or something like that. And thus indirectly document these kinds of
> requirements.
>

I would concur with this (and I have suggested exactly this in the past.)

	-hpa