linux-kernel - Re: IO space memcpy support for userspace.

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Message-ID: <119aab440812050932h9173a4bm79273b7ea8fe9a3a@mail.gmail.com>
Date:	Fri, 5 Dec 2008 12:32:04 -0500
From:	"Carlos O'Donell" <carlos@...temhalted.org>
To:	"Dave Airlie" <airlied@...il.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	libc-alpha@...rces.redhat.com
Subject: Re: IO space memcpy support for userspace.

On Thu, Dec 4, 2008 at 10:40 PM, Dave Airlie <airlied@...il.com> wrote:
> I'm sure this has come up before and I'm sure I'll either wish I never
> posted this or someone will show me the crisp corpse of the last guy
> who suggested it.

Do you plan to prevent the compiler from issuing the same sorts of
instructions that might appear in an optimized memcpy?

Isn't it dangerous to have memory that doesn't behave like normal
memory, and yet try to treat it like normal memory?

This mismatch of abstractions is a warning that must not be ignored.

IMHO you need a thin library with a new API (adding support for HAL
would be a clever way to check for PCI devices and perhaps even
mappings).

Cheers,
Carlos.
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