Date: Mon, 3 Feb 2014 11:58:55 +0300
From: Dan Carpenter <dan.carpenter@oracle.com>
To: Chen Gang <gang.chen.5i5j@gmail.com>
Cc: James Hogan <james.hogan@imgtec.com>, devel@driverdev.osuosl.org,
        andreas.dilger@intel.com, Antonio Quartulli <antonio@meshcoding.com>,
        Greg KH <gregkh@linuxfoundation.org>, bergwolf@gmail.com,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        David Miller <davem@davemloft.net>, oleg.drokin@intel.com,
        jacques-charles.lafoucriere@cea.fr, jinshan.xiong@intel.com,
        netdev <netdev@vger.kernel.org>, linux-metag@vger.kernel.org
Subject: Re: [PATCH] drivers: staging: lustre: lustre: include: add
 "__attribute__((packed))" for the related union
Message-ID: <20140203085855.GA26722@mwanda>
References: <20140118142404.GT7444@mwanda>
 <52DBA3D4.3090308@gmail.com>
 <52DD0EFF.2010305@imgtec.com>
 <20140120123045.GV7444@mwanda>
 <52DD18A5.1090308@imgtec.com>
 <20140120125603.GD4815@mwanda>
 <20140120211356.GG4815@mwanda>
 <52DE4DA3.7090301@imgtec.com>
 <52E3A642.7010307@gmail.com>
 <52ECFD53.7010401@gmail.com>
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Sender: linux-kernel-owner@vger.kernel.org

On Sat, Feb 01, 2014 at 09:57:39PM +0800, Chen Gang wrote:
> It seems, our kernel still stick to treate 'pack' region have effect
> with both 'align' and 'sizeof'.
> 

It's not about packed regions.  It's about unions.  It's saying the
sizeof() a union is a multiple of 4 unless it's packed.

union foo {
	short x;
	short y;
};

The author intended the sizeof(union foo) to be 2 but on metag arch then
it is 4.

regards,
dan carpenter

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