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Message-ID: <5b826dc7-2d02-d4ed-3b6a-63737abe732b@linaro.org> Date: Fri, 12 May 2023 11:24:50 +0200 From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org> To: Ivan Mikhaylov <fr0st61te@...il.com>, Samuel Mendoza-Jonas <sam@...dozajonas.com>, "David S . Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Rob Herring <robh+dt@...nel.org>, Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org> Cc: netdev@...r.kernel.org, devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, openbmc@...ts.ozlabs.org, Paul Fertser <fercerpav@...il.com> Subject: Re: [PATCH v2 3/5] dt-bindings: net: add mac-address-increment option On 12/05/2023 13:28, Ivan Mikhaylov wrote: > On Fri, 2023-05-12 at 08:22 +0200, Krzysztof Kozlowski wrote: >> On 11/05/2023 01:31, Ivan Mikhaylov wrote: >>> On Wed, 2023-05-10 at 16:48 +0200, Krzysztof Kozlowski wrote: >>>> On 09/05/2023 16:35, Ivan Mikhaylov wrote: >>>>> Add the mac-address-increment option for specify MAC address >>>>> taken >>>>> by >>>>> any other sources. >>>>> >>>>> Signed-off-by: Paul Fertser <fercerpav@...il.com> >>>>> Signed-off-by: Ivan Mikhaylov <fr0st61te@...il.com> >>>>> --- >>>>> .../devicetree/bindings/net/ethernet-controller.yaml | 8 >>>>> ++++++++ >>>>> 1 file changed, 8 insertions(+) >>>>> >>>>> diff --git a/Documentation/devicetree/bindings/net/ethernet- >>>>> controller.yaml >>>>> b/Documentation/devicetree/bindings/net/ethernet- >>>>> controller.yaml >>>>> index 00be387984ac..6900098c5105 100644 >>>>> --- a/Documentation/devicetree/bindings/net/ethernet- >>>>> controller.yaml >>>>> +++ b/Documentation/devicetree/bindings/net/ethernet- >>>>> controller.yaml >>>>> @@ -34,6 +34,14 @@ properties: >>>>> minItems: 6 >>>>> maxItems: 6 >>>>> >>>>> + mac-address-increment: >>>>> + $ref: /schemas/types.yaml#/definitions/int32 >>>>> + description: >>>>> + Specifies the MAC address increment to be added to the >>>>> MAC >>>>> address. >>>>> + Should be used in cases when there is a need to use MAC >>>>> address >>>>> + different from one obtained by any other level, like u- >>>>> boot >>>>> or the >>>>> + NC-SI stack. >>>> >>>> We don't store MAC addresses in DT, but provide simple >>>> placeholder >>>> for >>>> firmware or bootloader. Why shall we store static "increment" >>>> part of >>>> MAC address? Can't the firmware give you proper MAC address? >>>> >>>> Best regards, >>>> Krzysztof >>>> >>> >>> Krzysztof, maybe that's a point to make commit message with better >>> explanation from my side. At current time there is at least two >>> cases >>> where I see it's possible to be used: >>> >>> 1. NC-SI >>> 2. embedded >>> >>> At NC-SI level there is Get Mac Address command which provides to >>> BMC >>> mac address from the host which is same as host mac address, it >>> happens >>> at runtime and overrides old one. >>> >>> Also, this part was also to be discussed 2 years ago in this >>> thread: >>> https://lore.kernel.org/all/OF8E108F72.39D22E89-ON00258765.001E46EB-00258765.00251157@ibm.com/ >> >> Which was not sent to Rob though... >> >> >>> >>> Where Milton provided this information: >>> >>> DTMF spec DSP0222 NC-SI (network controller sideband interface) >>> is a method to provide a BMC (Baseboard management controller) >>> shared >>> access to an external ethernet port for comunication to the >>> management >>> network in the outside world. The protocol describes ethernet >>> packets >>> that control selective bridging implemented in a host network >>> controller >>> to share its phy. Various NIC OEMs have added a query to find out >>> the >>> address the host is using, and some vendors have added code to >>> query >>> host >>> nic and set the BMC mac to a fixed offset (current hard coded +1 >>> from >>> the host value). If this is compiled in the kernel, the NIC OEM is >>> recognised and the BMC doesn't miss the NIC response the address is >>> set >>> once each time the NCSI stack reinitializes. This mechanism >>> overrides >>> any mac-address or local-mac-address or other assignment. >>> >>> DSP0222 >>> https://www.dmtf.org/documents/pmci/network-controller-sideband-interface-nc-si-specification-110 >>> >>> >>> In embedded case, sometimes you have different multiple ethernet >>> interfaces which using one mac address which increments or >>> decrements >>> for particular interface, just for better explanation, there is >>> patch >>> with explanation which providing them such way of work: >>> https://github.com/openwrt/openwrt/blob/master/target/linux/generic/pending-5.15/682-of_net-add-mac-address-increment-support.patch >>> >>> In their rep a lot of dts using such option. >> >> None of these explain why this is property of the hardware. I >> understand >> that this is something you want Linux to do, but DT is not for that >> purpose. Do not encode system policies into DT and what above commit >> says is a policy. >> > > Krzysztof, okay then to which DT subsystem it should belong? To > ftgmac100 after conversion? To my understanding, decision to add some numbers to MAC address does not look like DT property at all. Otherwise please help me to understand - why different boards with same device should have different offset/value? Anyway, commit msg also lacks any justification for this. Best regards, Krzysztof
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