Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <be85bef7e144ebe08f422bf53bb81b59a130cb29.camel@gmail.com>
Subject: Re: [PATCH v2 3/5] dt-bindings: net: add mac-address-increment
 option
From:   Ivan Mikhaylov <fr0st61te@gmail.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>,
        Samuel Mendoza-Jonas <sam@mendozajonas.com>,
        "David S . Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>
Cc:     netdev@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, openbmc@lists.ozlabs.org,
        Paul Fertser <fercerpav@gmail.com>
Date:   Fri, 12 May 2023 11:28:37 +0000
In-Reply-To: <8de01e81-43dc-71af-f56f-4fba957b0b0b@linaro.org>
References: <20230509143504.30382-1-fr0st61te@gmail.com>
         <20230509143504.30382-4-fr0st61te@gmail.com>
         <6b5be71e-141e-c02a-8cba-a528264b26c2@linaro.org>
         <fc3dae42f2dfdf046664d964bae560ff6bb32f69.camel@gmail.com>
         <8de01e81-43dc-71af-f56f-4fba957b0b0b@linaro.org>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
User-Agent: Evolution 3.48.1 
MIME-Version: 1.0
Precedence: bulk

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.
> > > >=20
> > > > Signed-off-by: Paul Fertser <fercerpav@gmail.com>
> > > > Signed-off-by: Ivan Mikhaylov <fr0st61te@gmail.com>
> > > > ---
> > > > =C2=A0.../devicetree/bindings/net/ethernet-controller.yaml=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0 | 8
> > > > ++++++++
> > > > =C2=A01 file changed, 8 insertions(+)
> > > >=20
> > > > 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:
> > > > =C2=A0=C2=A0=C2=A0=C2=A0 minItems: 6
> > > > =C2=A0=C2=A0=C2=A0=C2=A0 maxItems: 6
> > > > =C2=A0
> > > > +=C2=A0 mac-address-increment:
> > > > +=C2=A0=C2=A0=C2=A0 $ref: /schemas/types.yaml#/definitions/int32
> > > > +=C2=A0=C2=A0=C2=A0 description:
> > > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 Specifies the MAC address increment=
 to be added to the
> > > > MAC
> > > > address.
> > > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 Should be used in cases when there =
is a need to use MAC
> > > > address
> > > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 different from one obtained by any =
other level, like u-
> > > > boot
> > > > or the
> > > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 NC-SI stack.
> > >=20
> > > 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?
> > >=20
> > > Best regards,
> > > Krzysztof
> > >=20
> >=20
> > 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:
> >=20
> > 1. NC-SI
> > 2. embedded
> >=20
> > 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.
> >=20
> > Also, this part was also to be discussed 2 years ago in this
> > thread:
> > https://lore.kernel.org/all/OF8E108F72.39D22E89-ON00258765.001E46EB-002=
58765.00251157@ibm.com/
>=20
> Which was not sent to Rob though...
>=20
>=20
> >=20
> > Where Milton provided this information:
> >=20
> > 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.=C2=A0 The protocol describes ethernet
> > packets=20
> > that control selective bridging implemented in a host network
> > controller
> > to share its phy.=C2=A0 Various NIC OEMs have added a query to find out
> > the=20
> > 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).=C2=A0 If this is compiled in the kernel, the NIC OEM i=
s
> > recognised and the BMC doesn't miss the NIC response the address is
> > set
> > once each time the NCSI stack reinitializes.=C2=A0 This mechanism
> > overrides
> > any mac-address or local-mac-address or other assignment.
> >=20
> > DSP0222
> > https://www.dmtf.org/documents/pmci/network-controller-sideband-interfa=
ce-nc-si-specification-110
> >=20
> >=20
> > 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/pen=
ding-5.15/682-of_net-add-mac-address-increment-support.patch
> >=20
> > In their rep a lot of dts using such option.
>=20
> 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.
>=20

Krzysztof, okay then to which DT subsystem it should belong? To
ftgmac100 after conversion?

Thanks.