linux-kernel - [PATCH] of: net: support NVMEM cells with MAC in text format

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Date:   Thu, 23 Dec 2021 13:27:47 +0100
From:   Rafał Miłecki <zajec5@...il.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Rob Herring <robh+dt@...nel.org>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>, netdev@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Rafał Miłecki <rafal@...ecki.pl>
Subject: [PATCH] of: net: support NVMEM cells with MAC in text format

From: Rafał Miłecki <rafal@...ecki.pl>

Some NVMEM devices have text based cells. In such cases MAC is stored in
a XX:XX:XX:XX:XX:XX format. Use mac_pton() to parse such data and
support those NVMEM cells. This is required to support e.g. a very
popular U-Boot and its environment variables.

Signed-off-by: Rafał Miłecki <rafal@...ecki.pl>
---
Please let me know if checking NVMEM cell length (6 B vs. 17 B) can be
considered a good enough solution. Alternatively we could use some DT
property to make it explicity, e.g. something like:

ethernet@...24000 {
	compatible = "brcm,amac";
	reg = <0x18024000 0x800>;

	nvmem-cells = <&mac_addr>;
	nvmem-cell-names = "mac-address";
	nvmem-mac-format = "text";
};
---
 net/core/of_net.c | 33 ++++++++++++++++++++++-----------
 1 file changed, 22 insertions(+), 11 deletions(-)

diff --git a/net/core/of_net.c b/net/core/of_net.c
index f1a9bf7578e7..95a64c813ae5 100644
--- a/net/core/of_net.c
+++ b/net/core/of_net.c
@@ -61,7 +61,7 @@ static int of_get_mac_addr_nvmem(struct device_node *np, u8 *addr)
 {
 	struct platform_device *pdev = of_find_device_by_node(np);
 	struct nvmem_cell *cell;
-	const void *mac;
+	const void *buf;
 	size_t len;
 	int ret;
 
@@ -78,21 +78,32 @@ static int of_get_mac_addr_nvmem(struct device_node *np, u8 *addr)
 	if (IS_ERR(cell))
 		return PTR_ERR(cell);
 
-	mac = nvmem_cell_read(cell, &len);
+	buf = nvmem_cell_read(cell, &len);
 	nvmem_cell_put(cell);
 
-	if (IS_ERR(mac))
-		return PTR_ERR(mac);
-
-	if (len != ETH_ALEN || !is_valid_ether_addr(mac)) {
-		kfree(mac);
-		return -EINVAL;
+	if (IS_ERR(buf))
+		return PTR_ERR(buf);
+
+	ret = 0;
+	if (len == ETH_ALEN) {
+		if (is_valid_ether_addr(buf))
+			memcpy(addr, buf, ETH_ALEN);
+		else
+			ret = -EINVAL;
+	} else if (len == 3 * ETH_ALEN - 1) {
+		u8 mac[ETH_ALEN];
+
+		if (mac_pton(buf, mac))
+			memcpy(addr, mac, ETH_ALEN);
+		else
+			ret = -EINVAL;
+	} else {
+		ret = -EINVAL;
 	}
 
-	memcpy(addr, mac, ETH_ALEN);
-	kfree(mac);
+	kfree(buf);
 
-	return 0;
+	return ret;
 }
 
 /**
-- 
2.31.1