netdev - Re: [PATCH] ethtool: Add QSFP-DD support

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Message-ID: <20191109153355.GK22978@lunn.ch>
Date:   Sat, 9 Nov 2019 16:33:55 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Adrian Pop <popadrian1996@...il.com>
Cc:     netdev@...r.kernel.org, linville@...driver.com
Subject: Re: [PATCH] ethtool: Add QSFP-DD support

On Sat, Nov 09, 2019 at 02:42:05PM +0200, Adrian Pop wrote:
> The Common Management Interface Specification (CMIS) for QSFP-DD shares
> some similarities with other form factors such as QSFP or SFP, but due to
> the fact that the module memory map is different, the current ethtool
> version is not able to provide relevant information about an interface.
> 
> This patch adds QSFP-DD support to ethtool. The changes are similar to
> the ones already existing in qsfp.c, but customized to use the memory
> addresses and logic as defined in the specifications document.
> 
> Page 0x00 (lower and higher memory) are always implemented, so the ethtool
> expects at least 256 bytes if the identifier matches the one for QSFP-DD.
> For optical connected cables, additional pages are usually available (the
> contain module defined  thresholds or lane diagnostic information). In
> this case, ethtool expects to receive 768 bytes in the following format:
> 
>     +----------+----------+----------+----------+----------+----------+
>     |   Page   |   Page   |   Page   |   Page   |   Page   |   Page   |
>     |   0x00   |   0x00   |   0x01   |   0x02   |   0x10   |   0x11   |
>     |  (lower) | (higher) | (higher) | (higher) | (higher) | (higher) |
>     |   128B   |   128B   |   128B   |   128B   |   128B   |   128B   |
>     +----------+----------+----------+----------+----------+----------

Hi Adrian

Which in kernel driver is using this format? As far as i can see, only
mlx5 makes use of ETH_MODULE_SFF_8436_MAX_LEN, which is 640
bytes. After a very quick look, i could not see any driver returning
768 bytes.

     Andrew