netdev - Re: [PATCH v2 net-next] sky2: use random address if EEPROM is bad

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Message-ID: <20150812093005.GV20890@e106497-lin.cambridge.arm.com>
Date:	Wed, 12 Aug 2015 10:30:05 +0100
From:	Liviu Dudau <Liviu.Dudau@....com>
To:	Stephen Hemminger <stephen@...workplumber.org>
Cc:	Florian Fainelli <f.fainelli@...il.com>,
	Mirko Lindner <mlindner@...vell.com>,
	"ryan.harkin@...aro.org" <ryan.harkin@...aro.org>,
	netdev <netdev@...r.kernel.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 net-next] sky2: use random address if EEPROM is bad

On Tue, Aug 11, 2015 at 06:01:32PM +0100, Stephen Hemminger wrote:
> On Tue, 11 Aug 2015 15:35:56 +0100
> Liviu Dudau <Liviu.Dudau@....com> wrote:
> 
> > On some embedded systems the EEPROM does not contain a valid MAC address.
> > In that case it is better to fallback to a generated mac address and
> > let init scripts fix the value later.
> > 
> > Reported-by: Liviu Dudau <Liviu.Dudau@....com>
> > Signed-off-by: Stephen Hemminger <stephen@...workplumber.org>
> > [Changed handcoded setup to use eth_hw_addr_random() instead]
> > Signed-off-by: Liviu Dudau <Liviu.Dudau@....com>
> > ---
> > I have tested this on my Juno platform and I can successfully do an nfsroot boot.
> > 
> > Best regards,
> > Liviu
> > 
> >  drivers/net/ethernet/marvell/sky2.c | 7 +++++++
> >  1 file changed, 7 insertions(+)
> > 
> > diff --git a/drivers/net/ethernet/marvell/sky2.c b/drivers/net/ethernet/marvell/sky2.c
> > index d9f4498..c309879 100644
> > --- a/drivers/net/ethernet/marvell/sky2.c
> > +++ b/drivers/net/ethernet/marvell/sky2.c
> > @@ -4819,6 +4819,13 @@ static struct net_device *sky2_init_netdev(struct sky2_hw *hw, unsigned port,
> >  		memcpy_fromio(dev->dev_addr, hw->regs + B2_MAC_1 + port * 8,
> >  			      ETH_ALEN);
> >  
> > +	/* if the address is invalid, use a random value */
> > +	if (!is_valid_ether_addr(dev->dev_addr)) {
> > +		netdev_warn(dev,
> > +			"Invalid MAC address, defaulting to random\n");
> > +		eth_hw_addr_random(dev);
> > +	}
> > +
> >  	return dev;
> >  }
> >  
> 
> This is not enough, you need to program the hardware with the new random MAC
> address. The easiest way is calling sky2_set_mac_address, but you need to convert
> the address from array back to sockaddr.
> 

OK, I am a bit confused as to why sky2_set_mac_address is needed here, as this was not
required by the existing function. Given that in my tests I get a random MAC address
assigned every time to the device and I can see the same MAC address with ifconfig, how
can I test the effect of sky2_set_mac_address if I add it?

Best regards,
Liviu

-- 
====================
| I would like to |
| fix the world,  |
| but they're not |
| giving me the   |
 \ source code!  /
  ---------------
    ¯\_(ツ)_/¯

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