linux-kernel - Re: [PATCH v2 2/3] net: add support for nvmem to eth_platform_get_mac

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Date:   Thu, 19 Jul 2018 15:37:22 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Bartosz Golaszewski <brgl@...ev.pl>
Cc:     Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Sekhar Nori <nsekhar@...com>,
        Kevin Hilman <khilman@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Grygorii Strashko <grygorii.strashko@...com>,
        "David S . Miller" <davem@...emloft.net>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Lukas Wunner <lukas@...ner.de>, Rob Herring <robh@...nel.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>,
        David Lechner <david@...hnology.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Lunn <andrew@...n.ch>,
        arm-soc <linux-arm-kernel@...ts.infradead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux-OMAP <linux-omap@...r.kernel.org>, netdev@...r.kernel.org
Subject: Re: [PATCH v2 2/3] net: add support for nvmem to
 eth_platform_get_mac_address()

On Thu, Jul 19, 2018 at 12:06:51PM +0200, Bartosz Golaszewski wrote:
> It looks simpler as long as you don't add all the new routines
> resulting from this approach. I've just tried to quickly implement
> this solution and it resulted in much bigger and duplicated code
> (checking the validity of mac_addr, copying it etc.). I would prefer
> the current approach and would like to read someone else's opinion on
> that.

It's not too bad.  There is two extra ether_addr_copy() calls and one
extra is_valid_ether_addr().  There are two extra alen declarations and
one extra addr declaration.  The functions don't share *that* much code.

regards,
dan carpenter

diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c
index fd8faa0dfa61..8ab7289a5069 100644
--- a/net/ethernet/eth.c
+++ b/net/ethernet/eth.c
@@ -54,6 +54,8 @@
 #include <linux/if_ether.h>
 #include <linux/of_net.h>
 #include <linux/pci.h>
+#include <linux/nvmem-consumer.h>
+#include <linux/mtd/mtd.h>
 #include <net/dst.h>
 #include <net/arp.h>
 #include <net/sock.h>
@@ -525,7 +527,7 @@ unsigned char * __weak arch_get_platform_mac_address(void)
 	return NULL;
 }
 
-int eth_platform_get_mac_address(struct device *dev, u8 *mac_addr)
+static int of_eth_get_mac_address(struct device *dev, u8 *mac_addr)
 {
 	const unsigned char *addr;
 	struct device_node *dp;
@@ -547,4 +549,82 @@ int eth_platform_get_mac_address(struct device *dev, u8 *mac_addr)
 	ether_addr_copy(mac_addr, addr);
 	return 0;
 }
+
+static int nvmem_eth_get_mac_address(struct device *dev, u8 *mac_addr)
+{
+	struct nvmem_cell *nvmem;
+	unsigned char *addr;
+	size_t alen;
+	int ret = 0;
+
+	nvmem = nvmem_cell_get(dev, "mac-address");
+	if (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))
+		return PTR_ERR(nvmem);
+	addr = nvmem_cell_read(nvmem, &alen);
+	if (IS_ERR(addr)) {
+		ret = PTR_ERR(addr);
+		goto put_nvmem;
+	}
+	if (alen != ETH_ALEN || !is_valid_ether_addr(addr)) {
+		ret = -EINVAL;
+		goto free_addr;
+	}
+	ether_addr_copy(mac_addr, addr);
+free_addr:
+	kfree(addr);
+put_nvmem:
+	nvmem_cell_put(nvmem);
+	return ret;
+}
+
+static int mtd_eth_get_mac_address(struct device *dev, u8 *mac_addr)
+{
+	struct mtd_info *mtd;
+	u8 addrbuf[ETH_ALEN];
+	size_t alen;
+	int ret;
+
+	/* This function should go away as soon as MTD gets nvmem support. */
+	if (!IS_ENABLED(CONFIG_MTD))
+		return -ENODEV;
+
+	mtd = get_mtd_device_nm("MAC-Address");
+	if (IS_ERR(mtd))
+		return PTR_ERR(mtd);
+	ret = mtd_read(mtd, 0, ETH_ALEN, &alen, addrbuf);
+	if (ret)
+		goto put_mtd;
+	if (!is_valid_ether_addr(addrbuf)) {
+		ret = -EINVAL;
+		goto put_mtd;
+	}
+	ether_addr_copy(mac_addr, addrbuf);
+put_mtd:
+	put_mtd_device(mtd);
+	return ret;
+}
+
+int eth_platform_get_mac_address(struct device *dev, u8 *mac_addr)
+{
+	int ret;
+
+	ret = of_eth_get_mac_address(dev, mac_addr);
+	if (!ret)
+		return 0;
+	ret = nvmem_eth_get_mac_address(dev, mac_addr);
+	if (ret == -EPROBE_DEFER)
+		return -EPROBE_DEFER;
+	if (!ret)
+		return 0;
+	ret = mtd_eth_get_mac_address(dev, mac_addr);
+	if (!ret)
+		return 0;
+
+	return -ENODEV;
+}
 EXPORT_SYMBOL(eth_platform_get_mac_address);