Subject: Re: [PATCH net-next 1/2] net: phy: sfp: make the i2c-bus property really optional

From: Antoine Tenart <[email-masked]>
Date: Thu, 17 May 2018 14:56:48 +0200

Hi Andrew,

On Thu, May 17, 2018 at 02:41:28PM +0200, Andrew Lunn wrote:
> On Thu, May 17, 2018 at 10:29:06AM +0200, Antoine Tenart wrote:
> > The SFF,SFP documentation is clear about making all the DT properties,
> > with the exception of the compatible, optional. In practice this is not
> > the case and without an i2c-bus property provided the SFP code will
> > throw NULL pointer exceptions.
> > 
> > This patch is an attempt to fix this.
> 
> How usable is an SFF/SFP module without access to the i2c EEPROM? I
> guess this comes down to link speed. Can it be manually configured?
>
> I'm just wondering if we want to make this mandatory? Fail the probe
> if it is not listed?

Yes, the other option would be to fail when probing a cage missing the
i2c description. I'd say a passive module can work without the i2c
EEPROM accessible as it does not need to be configured. I don't know
what would happen with active ones.

So the question is, do we want to enable partially working SFP cages
(ie. probably working with only a subset of SFP modules)?

Thanks!
Antoine

-- 
Antoine Ténart, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com