[PATCH v3 01/18] net: add helper eth_addr_add()

[Michael Walle <michael@walle.cc>]

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>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Jakub Kicinski <kuba@kernel.org>
---
changes since v2:
 - none

changes since v1:
 - none

 include/linux/etherdevice.h | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/include/linux/etherdevice.h b/include/linux/etherdevice.h
index a541f0c4f146..224645f17c33 100644
--- a/include/linux/etherdevice.h
+++ b/include/linux/etherdevice.h
@@ -507,6 +507,20 @@ 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);
+}
+
 /**
  * is_etherdev_addr - Tell if given Ethernet address belongs to the device.
  * @dev: Pointer to a device structure
-- 
2.30.2