netdev - RE: [PATCH v2] net: fec_mpc52xx: Read MAC address from device-tree

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Message-ID: <6A3DF150A5B70D4F9B66A25E3F7C888D065A1614@039-SN2MPN1-023.039d.mgd.msft.net>
Date:	Tue, 12 Feb 2013 11:23:24 +0000
From:	Bhushan Bharat-R65777 <R65777@...escale.com>
To:	Stefan Roese <sr@...x.de>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linuxppc-dev@...abs.org" <linuxppc-dev@...abs.org>,
	Anatolij Gustschin <agust@...x.de>,
	"David S. Miller" <davem@...emloft.net>
Subject: RE: [PATCH v2] net: fec_mpc52xx: Read MAC address from device-tree



> -----Original Message-----
> From: Stefan Roese [mailto:sr@...x.de]
> Sent: Tuesday, February 12, 2013 4:34 PM
> To: Bhushan Bharat-R65777
> Cc: netdev@...r.kernel.org; linuxppc-dev@...abs.org; Anatolij Gustschin; David
> S. Miller
> Subject: Re: [PATCH v2] net: fec_mpc52xx: Read MAC address from device-tree
> 
> On 12.02.2013 11:56, Bhushan Bharat-R65777 wrote:
> >> Until now, the MPC5200 FEC ethernet driver relied upon the bootloader
> >> (U-Boot) to write the MAC address into the ethernet controller
> >> registers. The Linux driver should not rely on such a thing. So lets
> >> read the MAC address from the DT as it should be done here.
> >>
> >> The following priority is now used to read the MAC address:
> >>
> >> 1) First, try OF node MAC address, if not present or invalid, then:
> >>
> >> 2) Read from MAC address registers, if invalid, then:
> >
> > Why we read from MAC registers if Linux should not rely on bootloader?
> 
> It was suggested by David. Backwards compatibility. Here Davids comment to my
> original patch which removed this register reading completely:
> 
> "
> I don't think this is a conservative enough change.
> 
> You have to keep the MAC register reading code around, as a backup code path in
> case the OF device node lacks a MAC address "

Ok,

But this is really a backward compatibility or hiding some bug? My thought is that if DT does not have a valid MAC address then it is a BUG and should be fixed. Is not it?

-Bharat

> 
> Thanks,
> Stefan


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