linux-kernel - Re: [PATCH net-next] net/ncsi: allow to customize BMC MAC Address offset

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Message-ID: <20190807184143.GE26047@lunn.ch>
Date:   Wed, 7 Aug 2019 20:41:43 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>
Cc:     Tao Ren <taoren@...com>,
        Samuel Mendoza-Jonas <sam@...dozajonas.com>,
        "David S . Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, openbmc@...ts.ozlabs.org,
        William Kennington <wak@...gle.com>,
        Joel Stanley <joel@....id.au>
Subject: Re: [PATCH net-next] net/ncsi: allow to customize BMC MAC Address
 offset

On Wed, Aug 07, 2019 at 11:25:18AM -0700, Jakub Kicinski wrote:
> On Tue, 6 Aug 2019 17:21:18 -0700, Tao Ren wrote:
> > Currently BMC's MAC address is calculated by adding 1 to NCSI NIC's base
> > MAC address when CONFIG_NCSI_OEM_CMD_GET_MAC option is enabled. The logic
> > doesn't work for platforms with different BMC MAC offset: for example,
> > Facebook Yamp BMC's MAC address is calculated by adding 2 to NIC's base
> > MAC address ("BaseMAC + 1" is reserved for Host use).
> > 
> > This patch adds NET_NCSI_MC_MAC_OFFSET config option to customize offset
> > between NIC's Base MAC address and BMC's MAC address. Its default value is
> > set to 1 to avoid breaking existing users.
> > 
> > Signed-off-by: Tao Ren <taoren@...com>
> 
> Maybe someone more knowledgeable like Andrew has an opinion here, 
> but to me it seems a bit strange to encode what seems to be platfrom
> information in the kernel config :(

Yes, this is not a good idea. It makes it impossible to have a 'BMC
distro' kernel which you install on a number of different BMCs.

A device tree property would be better. Ideally it would be the
standard local-mac-address, or mac-address.

  Andrew