Subject: Re: [PATCH RFC 13/26] sfp: add phylink based SFP module support

From: Florian Fainelli <[email-masked]>
Date: Thu, 07 Jan 2016 12:23:53 -0800

On 07/12/15 09:38, Russell King wrote:
> Add support for SFP hotpluggable modules via phylink.  This supports
> both copper and optical SFP modules, which require different Serdes
> modes in order to properly negotiate the link.
> 
> Optical SFP modules typically require the Serdes link to be talking
> 1000base-X mode - this is the gigabit ethernet mode defined by the
> 802.3 standard.
> 
> Copper SFP modules typically integrate a PHY in the module to convert
> from Serdes to copper, and the PHY will be configured by the vendor
> to either present a 1000base-X Serdes link (for fixed 1000base-T) or
> a SGMII Serdes link.  However, this is vendor defined, so we instead
> detect the PHY, switch the link to SGMII mode, and use traditional
> PHY based negotiation.

This goes pretty deep into the SFP specs, which I don't have a fresh
memory of, few nits here and there:

include/linux/sfp.h contains things that could be useful for user-space
since these are standard definitions, should this be moved to uapi such
that ethtool could use that header too?
-- 
Florian