linux-kernel - RE: [RFC PATCH 2/5] OMAP2+: add cpu id register to MAC address helper

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Message-ID: <B85A65D85D7EB246BE421B3FB0FBB593024C3B8670@dbde02.ent.ti.com>
Date:	Fri, 18 Mar 2011 20:07:55 +0530
From:	"Premi, Sanjeev" <premi@...com>
To:	Arnd Bergmann <arnd@...db.de>, Andy Green <andy@...mcat.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"patches@...aro.org" <patches@...aro.org>,
	Andy Green <andy.green@...aro.org>
Subject: RE: [RFC PATCH 2/5] OMAP2+: add cpu id register to MAC address
 helper

> -----Original Message-----
> From: linux-omap-owner@...r.kernel.org 
> [mailto:linux-omap-owner@...r.kernel.org] On Behalf Of Arnd Bergmann
> Sent: Friday, March 18, 2011 2:05 PM
> To: Andy Green
> Cc: linux-kernel@...r.kernel.org; linux-usb@...r.kernel.org; 
> linux-omap@...r.kernel.org; 
> linux-arm-kernel@...ts.infradead.org; patches@...aro.org; Andy Green
> Subject: Re: [RFC PATCH 2/5] OMAP2+: add cpu id register to 
> MAC address helper
> 
> On Saturday 12 March 2011, Andy Green wrote:
> > Introduce a generic helper function that can set a MAC address using
> > data from the OMAP unqiue CPU ID register.
> > 
> > Signed-off-by: Andy Green <andy.green@...aro.org>
> > ---
> > 
> >  arch/arm/mach-omap2/id.c              |   13 +++++++++++++
> >  arch/arm/mach-omap2/include/mach/id.h |    1 +
> >  2 files changed, 14 insertions(+), 0 deletions(-)
> > 
> > diff --git a/arch/arm/mach-omap2/id.c b/arch/arm/mach-omap2/id.c
> > index 5f9086c..fc69ec5 100644
> > --- a/arch/arm/mach-omap2/id.c
> > +++ b/arch/arm/mach-omap2/id.c
> > @@ -506,3 +506,16 @@ void __init 
> omap2_set_globals_tap(struct omap_globals *omap2_globals)
> >         else
> >                 tap_prod_id = 0x0208;
> >  }
> > +
> > +
> > +void omap2_die_id_to_mac(u8 *mac, int length)
> > +{
> > +       struct omap_die_id odi;
> > +
> > +       omap_get_die_id(&odi);
> > +       memcpy(mac, &odi.id_0, length);
> > +
> > +       /* mark it as not multicast and outside official 
> 80211 MAC namespace */
> > +
> > +       mac[0] = (mac[0] & ~1) | 2;
> > +}
> 
> This is a pretty clever trick, but it's not an official 
> globally unique MAC
> address, right?

[sp] This 'trick' has been tried earlier in u-boot. See:
     http://www.mail-archive.com/u-boot@lists.denx.de/msg19915.html

     I am also not sure whether DIE_ID would really be unique.

~sanjeev

> Maybe we can ask TI to officially request a 
> MAC address range
> for OMAP SoCs and document an official procedure to compute it.
> 
> 	Arnd
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