linux-kernel - Re: [PATCH 05/44 take 2] [UBI] internal common header

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Date:	Tue, 20 Feb 2007 15:15:55 +0000
From:	David Woodhouse <dwmw2@...radead.org>
To:	Theodore Tso <tytso@....edu>
Cc:	Artem Bityutskiy <dedekind@...radead.org>,
	Christoph Hellwig <hch@...radead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Frank Haverkamp <haver@...t.ibm.com>,
	Josh Boyer <jwboyer@...ux.vnet.ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 05/44 take 2] [UBI] internal common header

On Tue, 2007-02-20 at 09:55 -0500, Theodore Tso wrote:
> It appears that the reason why you are doing this is because you think
> you need the (packed) attribute.  Not needed; Linux assumes all over
> the place 16, 32, and 64 types are packed.  If Linux is ever compiled
> on an architecture where this isn't true, the compiler will probably
> need to be fixed so these assumptions are true, since all manner of
> things will break.

No, the packedness is irrelevant -- the reason is just to catch all the
places where you might otherwise forget to use byte-swapping accesses.

> It would be much better to use __be32 and __be64, so you get better
> type checking, and you will catch bugs caused by forgetting to use
> be32_to_cpu, et. al. 

The technique Artem uses is derived from what I do in JFFS2. It predates
the use of sparse to catch such errors, and works in gcc for _everyone_
without having to do anything special (like run sparse).

-- 
dwmw2

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