linux-kernel - Re: [PATCH v6 2/2] mctp pcc: Implement MCTP over PCC Transport

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Message-ID: <693f39f9-9505-4135-91db-a7280570fbc3@amperemail.onmicrosoft.com>
Date: Tue, 5 Nov 2024 15:16:20 -0500
From: Adam Young <admiyo@...eremail.onmicrosoft.com>
To: Jeremy Kerr <jk@...econstruct.com.au>, admiyo@...amperecomputing.com,
 Matt Johnston <matt@...econstruct.com.au>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 Sudeep Holla <sudeep.holla@....com>,
 Jonathan Cameron <Jonathan.Cameron@...wei.com>,
 Huisong Li <lihuisong@...wei.com>
Subject: Re: [PATCH v6 2/2] mctp pcc: Implement MCTP over PCC Transport

On 11/1/24 04:55, Jeremy Kerr wrote:
> Just to clarify that: for physical (ie, null-EID) addressing, you don't
> need the hardware address, you need:
>
>   1) the outgoing interface's ifindex; and
>   2) the hardware address of the*remote*  endpoint, in whatever
>      format is appropriate for link type

So Here is what I was thinking:

Lets ignore the namespace for now, as that is a future-proofing thing 
and will be all 0.  If The OS listens on index 11 and the PLatform 
listens index 22, the HW address for the OS would be

00001122

and for the Platform

00002211

This is all the info  for the calling application to know both the 
ifindex and the remote endpoint.

They can re-order the address to 00002211 for the remote endpoint.  If 
they have the link they have the ifindex.  It seems like a clean solution.

Adding the inbox id ( to the HW address does not harm anything, and it 
makes things much more explicit.

It seems like removing either the inbox or the outbox id from the HW 
address is hiding information that should be exposed.  And the two 
together make up the hardware addressing for the device, just not in 
that exact format, but it maps directly.  That is what will be in the 
upcoming version of the spec as well.