[RFC net-next 1/6] ethernet: add a helper for assigning port addresses

[Jakub Kicinski <kuba@kernel.org>]

We have 5 drivers which offset base MAC addr by port id.
Create a helper for them.

This helper takes care of overflows, which some drivers
did not do, please complain if that's going to break
anything!

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
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CC: linux-arm-kernel@lists.infradead.org
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---
 include/linux/etherdevice.h | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/include/linux/etherdevice.h b/include/linux/etherdevice.h
index 23681c3d3b8a..157f6c7ac9ff 100644
--- a/include/linux/etherdevice.h
+++ b/include/linux/etherdevice.h
@@ -551,6 +551,27 @@ static inline unsigned long compare_ether_header(const void *a, const void *b)
 #endif
 }
 
+/**
+ * eth_hw_addr_set_port - Generate and assign Ethernet address to a port
+ * @dev: pointer to port's net_device structure
+ * @base_addr: base Ethernet address
+ * @id: offset to add to the base address
+ *
+ * Assign a MAC address to the net_device using a base address and an offset.
+ * Commonly used by switch drivers which need to compute addresses for all
+ * their ports. addr_assign_type is not changed.
+ */
+static inline void eth_hw_addr_set_port(struct net_device *dev,
+					const u8 *base_addr, u8 id)
+{
+	u64 u = ether_addr_to_u64(base_addr);
+	u8 addr[ETH_ALEN];
+
+	u += id;
+	u64_to_ether_addr(u, addr);
+	eth_hw_addr_set(dev, addr);
+}
+
 /**
  * eth_skb_pad - Pad buffer to mininum number of octets for Ethernet frame
  * @skb: Buffer to pad
-- 
2.31.1