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

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Date:   Thu, 8 Aug 2019 04:48:25 +0000
From:   Tao Ren <taoren@...com>
To:     Andrew Lunn <andrew@...n.ch>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>
CC:     Samuel Mendoza-Jonas <sam@...dozajonas.com>,
        "David S . Miller" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "openbmc@...ts.ozlabs.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 8/7/19 11:41 AM, Andrew Lunn wrote:
> 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.

Thank you Andrew and Jakub for the feedback. I picked up kconfig approach mainly because it's an OEM-only extention which is used only when NCSI_OEM_CMD_GET_MAC is enabled.

Let me prepare patch v2 using device tree. I'm not sure if standard "mac-address" fits this situation because all we need is an offset (integer) and BMC MAC is calculated by adding the offset to NIC's MAC address. Anyways, let me work out v2 patch we can discuss more then.


Thanks,

Tao