netdev - Re: [patch net-next RFC 00/10] introduce line card support for modular switch

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Message-ID: <20210120154158.206b8752@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Wed, 20 Jan 2021 15:41:58 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Jiri Pirko <jiri@...nulli.us>, netdev@...r.kernel.org,
        davem@...emloft.net, jacob.e.keller@...el.com, roopa@...dia.com,
        mlxsw@...dia.com
Subject: Re: [patch net-next RFC 00/10] introduce line card support for
 modular switch

On Wed, 20 Jan 2021 14:56:46 +0100 Andrew Lunn wrote:
> > No, the FW does not know. The ASIC is not physically able to get the
> > linecard type. Yes, it is odd, I agree. The linecard type is known to
> > the driver which operates on i2c. This driver takes care of power
> > management of the linecard, among other tasks.  
> 
> So what does activated actually mean for your hardware? It seems to
> mean something like: Some random card has been plugged in, we have no
> idea what, but it has power, and we have enabled the MACs as
> provisioned, which if you are lucky might match the hardware?
> 
> The foundations of this feature seems dubious.

But Jiri also says "The linecard type is known to the driver which
operates on i2c." which sounds like there is some i2c driver (in user
space?) which talks to the card and _does_ have the info? Maybe I'm
misreading it. What's the i2c driver?