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Date:   Tue, 25 Jan 2022 11:24:52 +0100
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Subject: Re: [PATCH 5/8] net: add helper eth_addr_add()
To:     Michael Walle <michael@walle.cc>, linux-mtd@lists.infradead.org,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, netdev@vger.kernel.org
Cc:     Miquel Raynal <miquel.raynal@bootlin.com>,
        Richard Weinberger <richard@nod.at>,
        Vignesh Raghavendra <vigneshr@ti.com>,
        Rob Herring <robh+dt@kernel.org>,
        Srinivas Kandagatla <srinivas.kandagatla@linaro.org>,
        Shawn Guo <shawnguo@kernel.org>, Li Yang <leoyang.li@nxp.com>,
        Frank Rowand <frowand.list@gmail.com>,
        "David S . Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Ansuel Smith <ansuelsmth@gmail.com>,
        Andrew Lunn <andrew@lunn.ch>
References: <20211228142549.1275412-1-michael@walle.cc>
 <20211228142549.1275412-6-michael@walle.cc>
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In-Reply-To: <20211228142549.1275412-6-michael@walle.cc>
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On 28.12.2021 15:25, Michael Walle wrote:
> Add a helper to add an offset to a ethernet address. This comes in handy
> if you have a base ethernet address for multiple interfaces.
> 
> Signed-off-by: Michael Walle <michael@walle.cc>
> ---
>   include/linux/etherdevice.h | 14 ++++++++++++++
>   1 file changed, 14 insertions(+)
> 
> diff --git a/include/linux/etherdevice.h b/include/linux/etherdevice.h
> index 2ad71cc90b37..9d621dc85290 100644
> --- a/include/linux/etherdevice.h
> +++ b/include/linux/etherdevice.h
> @@ -486,6 +486,20 @@ static inline void eth_addr_inc(u8 *addr)
>   	u64_to_ether_addr(u, addr);
>   }
>   
> +/**
> + * eth_addr_add() - Add (or subtract) and offset to/from the given MAC address.
> + *
> + * @offset: Offset to add.
> + * @addr: Pointer to a six-byte array containing Ethernet address to increment.
> + */
> +static inline void eth_addr_add(u8 *addr, long offset)
> +{
> +	u64 u = ether_addr_to_u64(addr);
> +
> +	u += offset;
> +	u64_to_ether_addr(u, addr);
> +}

Please check eth_hw_addr_gen() which contains identical code +
eth_hw_addr_set().

You should probably make eth_hw_addr_gen() use your new function as a
helper.