linux-kernel - Re: 2.6.18-rc5-mm1: drivers/infiniband/hw/amso1100/c2.c compile error

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Message-ID: <20060901204343.GA4979@flint.arm.linux.org.uk>
Date:	Fri, 1 Sep 2006 21:43:43 +0100
From:	Russell King <rmk+lkml@....linux.org.uk>
To:	Andrew Morton <akpm@...l.org>
Cc:	Roland Dreier <rdreier@...co.com>, Adrian Bunk <bunk@...sta.de>,
	Tom Tucker <tom@...ngridcomputing.com>,
	Steve Wise <swise@...ngridcomputing.com>,
	Roland Dreier <rolandd@...co.com>,
	linux-kernel@...r.kernel.org, openib-general@...nib.org,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: 2.6.18-rc5-mm1: drivers/infiniband/hw/amso1100/c2.c compile error

On Fri, Sep 01, 2006 at 01:04:44PM -0700, Andrew Morton wrote:
> On Fri, 01 Sep 2006 12:53:47 -0700
> Roland Dreier <rdreier@...co.com> wrote:
> > Yes, I agree that's a good plan, especially the documentation part.
> > However I would argue that what's in drivers/infiniband/hw/mthca/mthca_doorbell.h 
> > is legitimate: the driver uses __raw_writeq() when it exists and uses
> > two __raw_writel()s properly serialized with a device-specific lock to
> > get exactly the atomicity it needs on 32-bit archs.
> 
> No, driver-specific workarounds are not legitimate, sorry.
> 
> The driver should simply fail to compile on architectures which do not
> implement __raw_writeq().

So, what you're basically saying is that on architectures which can _NOT_
implement an atomic __raw_writeq(), certain drivers simply will not be
available?

> We can speed up the process by sending helpful emails to architecture
> maintainers, but they'll notice either way.

I think you're completely wrong in the context of the message you're
replying to - it's talking about an _atomic_ 64-bit write.

Sure, if you want a _non-atomic_ 64-bit write then that's possible,
but many 32-bit architectures can't do a 64-bit atomic IO write and
that isn't something they can "fix".

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:  2.6 Serial core

-- 
VGER BF report: H 5.55112e-17
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