linux-kernel - Re: [PATCH] usb: file-storage.c use unaligned access helpers

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Message-ID: <Pine.LNX.4.44L0.0805161021450.25035-100000@netrider.rowland.org>
Date:	Fri, 16 May 2008 10:32:10 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Harvey Harrison <harvey.harrison@...il.com>
cc:	Bryan Wu <cooloney@...nel.org>, Jie Zhang <jie.zhang@...log.com>,
	Oliver Neukum <oliver@...kum.org>, <david-b@...bell.net>,
	<greg@...ah.com>, <linux-usb@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] usb: file-storage.c use unaligned access helpers

On Thu, 15 May 2008, Harvey Harrison wrote:

> Replace the put_be16/32 and get_be16/32 helpers with the
> common unaligned access routines.  Note that these put_ helpers
> had the pointer/value parameter in the opposite order from the
> common version.

This is fine and it's what I requested.  Still, it's not really the 
best solution.

In many of the places where these helpers are used, we _know_ that the
buffers are in fact aligned properly.  For example, in code like this:

> -			put_be16(&buf[4], 0xffff);
> +			put_unaligned_be16(0xffff, &buf[4]);

we know that buf is aligned.  It would be great if there were helpers 
which would allow us to do

			put_be16(&buf[4], 0xffff);

instead of

			* (__be16 *) &buf[4] = cpu_to_be16(0xffff);

They could also be used to clean up the disputed HCD code.  Is this a
reasonable thing to ask for?  A few simple, arch-independent macros
would be sufficient.

Alan Stern

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