netdev - Re: [PATCH v3 05/10] net/fec: add dual fec support for mx28

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Date:	Fri, 7 Jan 2011 10:44:49 +0100
From:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
To:	Shawn Guo <shawn.guo@...escale.com>
Cc:	davem@...emloft.net, gerg@...pgear.com, baruch@...s.co.il,
	eric@...rea.com, bryan.wu@...onical.com, r64343@...escale.com,
	B32542@...escale.com, lw@...o-electronics.de,
	w.sang@...gutronix.de, s.hauer@...gutronix.de,
	netdev@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 05/10] net/fec: add dual fec support for mx28

Hello,

On Fri, Jan 07, 2011 at 03:00:57PM +0800, Shawn Guo wrote:
> On Thu, Jan 06, 2011 at 08:10:47AM +0100, Uwe Kleine-König wrote:
> > Hello Shawn,
> > 
> [...]
> > > > > +     /*
> > > > > +      * enet-mac reset will reset mac address registers too,
> > > > > +      * so need to reconfigure it.
> > > > > +      */
> > > > > +     if (fec_is_enetmac) {
> > > > > +             memcpy(&temp_mac, dev->dev_addr, ETH_ALEN);
> > > 		  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > > > > +             writel(cpu_to_be32(temp_mac[0]), fep->hwp + FEC_ADDR_LOW);
> > > > > +             writel(cpu_to_be32(temp_mac[1]), fep->hwp + FEC_ADDR_HIGH);
> > > > where is the value saved to temp_mac[]?  For me it looks you write
> > > > uninitialized data into the mac registers.
> > > 
> > > memcpy above.
> > oops.  right.  I looked for something like
> > 
> > 	temp_mac[0] = dev->dev_addr[0] << $shiftfor0 | ...
> > 
> > which AFAIK is what you want here.  memcpy is sensible to (at least)
> > endian issues.  If you ask me factor out the setting of the mac address
> > in probe to a function and use that here, too.
> > 
> The memcpy of mac address is being widely used in fec and other
> network drivers, and I do not prefer to change something so common
> in this patch set.
Hmm, fec_get_mac uses memcpy as does fec_set_mac_address.
fec_enet_init uses mask and shift.  When writing my comment I only saw
the latter.  Having that uniform and only in two places (one for setting
and for reading) would be great.

Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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