linux-kernel - Re: [PATCH v1 1/5] ARM: imx28: add basic dt support

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Message-ID: <20120316030521.GB5161@shlinux2.ap.freescale.net>
Date:	Fri, 16 Mar 2012 11:05:21 +0800
From:	Dong Aisheng <aisheng.dong@...escale.com>
To:	"s.hauer@...gutronix.de" <s.hauer@...gutronix.de>
CC:	Dong Aisheng-B29396 <B29396@...escale.com>,
	Lothar Waßmann <LW@...O-electronics.de>,
	Guo Shawn-R65073 <r65073@...escale.com>,
	"vinod.koul@...ux.intel.com" <vinod.koul@...ux.intel.com>,
	"devicetree-discuss@...ts.ozlabs.org" 
	<devicetree-discuss@...ts.ozlabs.org>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	Grant Likely <grant.likely@...retlab.ca>,
	"rdunlap@...otime.net" <rdunlap@...otime.net>,
	"kernel@...gutronix.de" <kernel@...gutronix.de>,
	"cjb@...top.org" <cjb@...top.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v1 1/5] ARM: imx28: add basic dt support

On Thu, Mar 15, 2012 at 07:24:19PM +0800, s.hauer@...gutronix.de wrote:
> On Thu, Mar 15, 2012 at 06:59:28PM +0800, Dong Aisheng wrote:
> > On Thu, Mar 15, 2012 at 02:53:29PM +0800, Lothar Waßmann wrote:
> > > Hi,
> > > 
> > > Dong Aisheng writes:
> > > > On Wed, Mar 14, 2012 at 10:16:43PM +0800, s.hauer@...gutronix.de wrote:
> > > > > On Wed, Mar 14, 2012 at 08:45:23PM +0800, Dong Aisheng wrote:
> > > > > > On Wed, Mar 14, 2012 at 01:23:51AM +0800, Grant Likely wrote:
> > > [...]
> > > > > > But it seems this needs pass mac address to fec driver via platforom data which is
> > > > > > not friendly to dt.
> > > > > > 
> > > > > > Another way may be changing fec driver to get the fixed part of mac address(first
> > > > > > two bytes) from device tree and read the left dynamical part from otp which i'm not
> > > > > > sure is better enough.
> > > > > > 
> > > > > > BTW, filling with zeros seems not work since it's invalid mac address.
> > > > > 
> > > > > Yes, that's the idea of using this value...
> > > > > 
> > > > But comparing to use an invalid value, why not just do not define that
> > > > local-mac-address property?
> > > > 
> > > Because a MAC address is by definition a GLOBALLY UNIQUE IDENTIFIER
> > > which is contrary to coding a "valid" default value for it somewhere!
> > > The owner of a certain MAC address range (OUI) is responsible for
> > > ensuring the uniqueness. Thus only they may assign a specific MAC
> > > address to a specific device.
> > > 
> > Yes, you're correct.
> > So i propose to read the MAC address from MX28 OTP in fec driver instead of
> > define it in device tree in my last mail.
> > http://www.spinics.net/lists/arm-kernel/msg165040.html
> > Do you have any comment on that way?
> 
> Yes, you could do that. Otherwise it's perfectly fine to pass the MAC
> address in the device tree, it's just not ok to put specific values
> into the kernel source. You could leave the values blank and let the
Yes, correct.

> bootloader fill them in. Or you could fill in valid values before you
> compile the devicetree, but be prepared for surprises once you have
> two boards in your network and use the devicetree for both.
> 

Thanks for the info.
I will submit that patch for discussion.

Regards
Dong Aisheng

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