linux-kernel - Re: [PATCH 1/2] drivers/misc/eeprom/men_eeprod: Introduce MEN Board Information EEPROM driver

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Message-ID: <20141016093414.GA25214@kroah.com>
Date:	Thu, 16 Oct 2014 11:34:14 +0200
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Wolfram Sang <wsa@...-dreams.de>
Cc:	Andreas Werner <andreas.werner@....de>,
	linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org,
	johannes.thumshirn@....de
Subject: Re: [PATCH 1/2] drivers/misc/eeprom/men_eeprod: Introduce MEN Board
 Information EEPROM driver

On Thu, Oct 16, 2014 at 10:58:35AM +0200, Wolfram Sang wrote:
> > +struct eeprom_data {
> > +	uint8_t eeprod_id;
> > +
> > +	uint8_t revision[3];
> > +	uint32_t serialnr;
> > +	uint8_t board_model;
> > +	char hw_name[6];
> > +
> > +	uint8_t reserved;
> > +
> > +	__be16 prod_date;
> > +	__be16 rep_date;
> > +
> > +	uint8_t reserved2[4];
> > +};
> 
> And what if the compiler reorders?

It's not allowed to reorder, but it can add padding wherever it wants
to, which if this is a on-device structure, can cause problems.  Use
__packed to prevent that.

thanks,

greg k-h
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