netdev - RE: [PATCH 10/14] net: dsa/mv88e6352: Implement EEPROM accessfunctions

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Date:	Thu, 23 Oct 2014 18:41:59 +0000
From:	Chris Healy <chealy@...co-us.com>
To:	Guenter Roeck <linux@...ck-us.net>, Andrew Lunn <andrew@...n.ch>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Florian Fainelli <f.fainelli@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 10/14] net: dsa/mv88e6352: Implement EEPROM
 	accessfunctions

Hi Guenter,

I do not believe it is possible to know if an EEPROM is attached or not.

Chris
________________________________________
From: Guenter Roeck [linux@...ck-us.net]
Sent: Thursday, October 23, 2014 9:40 AM
To: Andrew Lunn
Cc: netdev@...r.kernel.org; David S. Miller; Florian Fainelli; linux-kernel@...r.kernel.org; Chris Healy
Subject: Re: [PATCH 10/14] net: dsa/mv88e6352: Implement EEPROM         accessfunctions

On Thu, Oct 23, 2014 at 03:54:12PM +0200, Andrew Lunn wrote:
> On Wed, Oct 22, 2014 at 09:03:18PM -0700, Guenter Roeck wrote:
> > MV88E6352 supports read and write access to its configuration eeprom.
>
> Hi Guenter
>
> I don't have the datasheet for the MV88E6352. Is the EEPROM built in,
> or external on an i2c bus?
>
External.

> > +static int mv88e6352_get_eeprom_len(struct dsa_switch *ds)
> > +{
> > +   return 0x200;
> > +}
>
> How do you handle the case of it being external and not populated.
> Would it not be better to try to detect it here, and return 0 if it
> does not exist?
>
Makes sense, if it is detectable that it the EEPROM not there. Browsing
through the datasheet, I don't see how I could detect it; there does not
seem to be a status bit indicating if the EEPROM is there or not. There
are sw_mode pins which determine if the eeprom should be loaded after
reset or not, but I don't see anything in the register set which would
tell me.

Chris, do you know if there is a means to detect if the EEPROM is present
on the MV88E6352 ?

Thanks,
Guenter

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