[PATCH 4/5] net: add support for nvmem to eth_platform_get_mac_address()

[Bartosz Golaszewski <brgl@bgdev.pl>]

From: Bartosz Golaszewski <bgolaszewski@baylibre.com>

Many non-DT platforms read the MAC address from EEPROM. Usually it's
either done with callbacks defined in board files or from SoC-specific
ethernet drivers.

In order to generalize this, try to read the MAC from nvmem in
eth_platform_get_mac_address() using a standard lookup name:
"mac-address".

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
---
 net/ethernet/eth.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c
index 6b64586fd2af..adf5bd03851f 100644
--- a/net/ethernet/eth.c
+++ b/net/ethernet/eth.c
@@ -54,6 +54,7 @@
 #include <linux/if_ether.h>
 #include <linux/of_net.h>
 #include <linux/pci.h>
+#include <linux/nvmem-consumer.h>
 #include <net/dst.h>
 #include <net/arp.h>
 #include <net/sock.h>
@@ -530,7 +531,10 @@ int eth_platform_get_mac_address(struct device *dev, u8 *mac_addr)
 	struct device_node *dp = dev_is_pci(dev) ?
 			pci_device_to_OF_node(to_pci_dev(dev)) : dev->of_node;
 	const unsigned char *addr = NULL;
+	unsigned char addrbuf[ETH_ALEN];
+	struct nvmem_cell *nvmem;
 	const char *from = NULL;
+	size_t alen;
 
 	if (dp) {
 		addr = of_get_mac_address(dp);
@@ -544,6 +548,31 @@ int eth_platform_get_mac_address(struct device *dev, u8 *mac_addr)
 			from = "arch callback";
 	}
 
+	if (!addr) {
+		nvmem = nvmem_cell_get(dev, "mac-address");
+		if (IS_ERR(nvmem) && PTR_ERR(nvmem) == -EPROBE_DEFER)
+			/* We may have a lookup registered for MAC address but
+			 * the corresponding nvmem provider hasn't been
+			 * registered yet.
+			 */
+			return -EPROBE_DEFER;
+
+		if (!IS_ERR(nvmem)) {
+			addr = nvmem_cell_read(nvmem, &alen);
+			if (!IS_ERR(addr)) {
+				from = "nvmem";
+				/* Don't use ether_addr_copy() in case we
+				 * didn't get the right size.
+				 */
+				memcpy(addrbuf, addr, alen);
+				kfree(addr);
+				addr = addrbuf;
+			}
+
+			nvmem_cell_put(nvmem);
+		}
+	}
+
 	if (!addr || !is_valid_ether_addr(addr))
 		return -ENODEV;
 
-- 
2.17.1