Question abount VSOL/CarlitoxxPro SFP Patch on Marvell Armada (MCBIN DS)

[Russell King (Oracle)]

On Sun, May 08, 2022 at 06:51:59PM +0200, Pali Rohár wrote:
> Russell, is there any option to ignore speed information stored in SFP
> EEPROM and try to choose speed at linux runtime?

If sfp_parse_support() fills in a support mask containing both
1000base-X and 2500base-X, then yes. By default, phylink will choose
2500base-X because that's the fastest speed. ethtool will report that
both 1000base-X and 2500base-X is supported, and 2500base-X is being
advertised.

If you change the advertisement to 1000base-X, then phylink will switch
to 1000base-X, and vice versa.

> And how to correctly handle behavior of SFP module which changes speed
> during usage time?

I know of no way that a SFP module can signal to the host that its host
interface has changed in some way. There is no provision for a module to
state what the host interface actually is of the module - most of what
the kernel does is heuristics based on modules that I've had available.

SFPs suck in this regard. GPON SFPs suck way harder because they claim
SFP MSA compliance but they always seem to be violating the SFP MSA in
some regard.

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