linux-kernel - Re: Opinion on ordering of writel vs. stores to RAM

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Date:	Tue, 12 Sep 2006 10:49:07 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	David Miller <davem@...emloft.net>
Cc:	segher@...nel.crashing.org, jbarnes@...tuousgeek.org,
	jeff@...zik.org, paulus@...ba.org, torvalds@...l.org,
	linux-kernel@...r.kernel.org, akpm@...l.org
Subject: Re: Opinion on ordering of writel vs. stores to RAM


> It's silly because if you just use different interface
> names for the different semantics, the caller can
> ask for what he wants at the call site and no conditionals
> are needed in the implementation.

As Paulus also pointed out, having writel() behave differently based on
some magic done earlier at map time makes it harder to understand what
happens when reading the code, and thus harder to audit drivers for
missing barriers etc... since it's not obvious at first sight wether a
driver is using ordered or relaxed semantics. Thus I prefer keeping two
speparate interfaces.

We've come up with the __writel() name, but I'm open to proposals for
something nicer :)

Ben.

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