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