Date: Tue, 21 Jun 2011 10:58:19 -0400 (EDT)
From: Alan Stern <stern@rowland.harvard.edu>
To: Nicolas Pitre <nico@fluxnic.net>
cc: Alexander Holler <holler@ahsoftware.de>, Arnd Bergmann <arnd@arndb.de>,
        <linux-arm-kernel@lists.infradead.org>, <linux-usb@vger.kernel.org>,
        <gregkh@suse.de>, lkml <linux-kernel@vger.kernel.org>,
        Rabin Vincent <rabin@rab.in>
Subject: Re: [PATCH] USB: ehci: use packed,aligned(4) instead of removing
 the packed attribute
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On Mon, 20 Jun 2011, Nicolas Pitre wrote:

> > We don't fall into any of these cases, and therefore as you say, we
> > don't need packed.  Arnd and I have both explained this.  So why do you 
> > keep arguing that we do need it?
> 
> Please show me where I keep arguing that you need it?

Not explicitly perhaps.  But you did write:

> Doesn't mean that because it used to work that it is strictly correct.  
> Wouldn't be the first time that a GCC upgrade broke the kernel because 
> the kernel wasn't describing things properly enough.

which strongly implies that "packed" is needed.  You also wrote:

> Yes, but that's a consequence of not being able to access those fields 
> in their naturally aligned position anymore.  Hence the addition of the 
> align attribute to tell the compiler that we know that the structure is 
> still aligned to a certain degree letting the compiler to avoid 
> byte-oriented instructions when possible.

which is predicated on the assumption that "packed" is needed.

Alan Stern

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