linux-kernel - Re: [PATCH v3] net: sfp: handle 100G/25G active optical cables in sfp_parse

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Message-ID: <ZN9X97YntVZkw3PG@shell.armlinux.org.uk>
Date:   Fri, 18 Aug 2023 12:37:27 +0100
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Josua Mayer <josua@...id-run.com>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH v3] net: sfp: handle 100G/25G active optical cables in
 sfp_parse_support

On Fri, Aug 18, 2023 at 01:05:56PM +0200, Josua Mayer wrote:
> Handle extended compliance code 0x1 (SFF8024_ECC_100G_25GAUI_C2M_AOC)
> for active optical cables supporting 25G and 100G speeds.
> 
> Since the specification makes no statement about transmitter range, and
> as the specific sfp module that had been tested features only 2m fiber -
> short-range (SR) modes are selected.
> 
> The 100G speed is irrelevant because it would require multiple fibers /
> multiple SFP28 modules combined under one netdev.
> sfp-bus.c only handles a single module per netdev, so only 25Gbps modes
> are selected.
> 
> sfp_parse_support already handles SFF8024_ECC_100GBASE_SR4_25GBASE_SR
> with compatible properties, however that entry is a contradiction in
> itself since with SFP(28) 100GBASE_SR4 is impossible - that would likely
> be a mode for qsfp modules only.
> 
> Add a case for SFF8024_ECC_100G_25GAUI_C2M_AOC selecting 25gbase-r
> interface mode and 25000baseSR link mode.
> Also enforce SFP28 bitrate limits on the values read from sfp eeprom as
> requested by Russell King.
> 
> Tested with fs.com S28-AO02 AOC SFP28 module.
> 
> Signed-off-by: Josua Mayer <josua@...id-run.com>

Reviewed-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>

Thanks!

-- 
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