From: "H. Peter Anvin" <hpa@zytor.com>
To: linux-kernel@vger.kernel.org
Subject: Re: memcpy_toio on i386 using byte writes even when n%2==0
Date: Mon, 29 May 2006 00:38:05 -0700 (PDT) [thread overview]
Message-ID: <e5e8ct$bl6$1@terminus.zytor.com> (raw)
In-Reply-To: 44779358.9010703@shaw.ca
Followup to: <44779358.9010703@shaw.ca>
By author: Robert Hancock <hancockr@shaw.ca>
In newsgroup: linux.dev.kernel
>
> It does seem a little bit less efficient, but I don't know think it's
> necessarily a bug. There's no guarantee of what size writes will be used
> with the memcpy_to/fromio functions.
>
There are only a few semantics that make sense: fixed 8, 16, 32, or 64
bits, plus "optimal"; the latter to be used for anything that doesn't
require a specific transfer size. Logically, an unqualified
"memcpy_to/fromio" should be the optimal size (as few transfers as
possible) -- we have a qualified "memcpy_to/fromio32" already, and 8-
and 16-bit variants could/should be added.
However, having the unqualified version do byte transfers seems like a
really bad idea.
-hpa
next prev parent reply other threads:[~2006-05-29 7:38 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <6gMqr-8uW-23@gated-at.bofh.it>
2006-05-26 23:46 ` memcpy_toio on i386 using byte writes even when n%2==0 Robert Hancock
2006-05-29 7:38 ` H. Peter Anvin [this message]
2006-05-30 13:55 ` Chris Lesiak
2006-05-30 14:24 ` linux-os (Dick Johnson)
[not found] <6ined-4gY-17@gated-at.bofh.it>
[not found] ` <6ined-4gY-21@gated-at.bofh.it>
[not found] ` <6inee-4gY-23@gated-at.bofh.it>
[not found] ` <6ined-4gY-15@gated-at.bofh.it>
[not found] ` <6inxv-4U2-17@gated-at.bofh.it>
2006-06-03 23:52 ` Robert Hancock
2006-06-04 0:48 ` H. Peter Anvin
[not found] <6gUec-3mb-7@gated-at.bofh.it>
[not found] ` <6gUec-3mb-5@gated-at.bofh.it>
[not found] ` <6icVy-56r-9@gated-at.bofh.it>
[not found] ` <6idov-5Tc-7@gated-at.bofh.it>
2006-05-31 0:55 ` Robert Hancock
2006-05-31 1:13 ` H. Peter Anvin
2006-05-26 15:29 Chris Lesiak
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