nvmem: brcm_nvram: add .read_post_process() for MACs

1. Parse ASCII MAC format into byte based
2. Calculate relative addresses based on index argument
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Message-ID: <20230611140330.154222-5-srinivas.kandagatla@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/nvmem/Kconfig

@@ -55,6 +55,7 @@ config NVMEM_BRCM_NVRAM
 	tristate "Broadcom's NVRAM support"
 	depends on ARCH_BCM_5301X || COMPILE_TEST
 	depends on HAS_IOMEM
+	select GENERIC_NET_UTILS
 	help
 	  This driver provides support for Broadcom's NVRAM that can be accessed
 	  using I/O mapping.

drivers/nvmem/brcm_nvram.c

@@ -4,6 +4,8 @@
  */
 
 #include <linux/bcm47xx_nvram.h>
+#include <linux/etherdevice.h>
+#include <linux/if_ether.h>
 #include <linux/io.h>
 #include <linux/mod_devicetable.h>
 #include <linux/module.h>
@@ -42,6 +44,25 @@ static int brcm_nvram_read(void *context, unsigned int offset, void *val,
 	return 0;
 }
 
+static int brcm_nvram_read_post_process_macaddr(void *context, const char *id, int index,
+						unsigned int offset, void *buf, size_t bytes)
+{
+	u8 mac[ETH_ALEN];
+
+	if (bytes != 3 * ETH_ALEN - 1)
+		return -EINVAL;
+
+	if (!mac_pton(buf, mac))
+		return -EINVAL;
+
+	if (index)
+		eth_addr_add(mac, index);
+
+	ether_addr_copy(buf, mac);
+
+	return 0;
+}
+
 static int brcm_nvram_add_cells(struct brcm_nvram *priv, uint8_t *data,
 				size_t len)
 {
@@ -75,6 +96,13 @@ static int brcm_nvram_add_cells(struct brcm_nvram *priv, uint8_t *data,
 		priv->cells[idx].offset = value - (char *)data;
 		priv->cells[idx].bytes = strlen(value);
 		priv->cells[idx].np = of_get_child_by_name(dev->of_node, priv->cells[idx].name);
+		if (!strcmp(var, "et0macaddr") ||
+		    !strcmp(var, "et1macaddr") ||
+		    !strcmp(var, "et2macaddr")) {
+			priv->cells[idx].raw_len = strlen(value);
+			priv->cells[idx].bytes = ETH_ALEN;
+			priv->cells[idx].read_post_process = brcm_nvram_read_post_process_macaddr;
+		}
 	}
 
 	return 0;