Re: [PATCH v4 01/10] of_net: add NVMEM support to of_get_mac_address

Many embedded devices have information such as MAC addresses stored
inside NVMEMs like EEPROMs and so on. Currently there are only two
drivers in the tree which benefit from NVMEM bindings.

Adding support for NVMEM into every other driver would mean adding a lot
of repetitive code. This patch allows us to configure MAC addresses in
various devices like ethernet and wireless adapters directly from
of_get_mac_address, which is already used by almost every driver in the
tree.

Predecessor of this patch which used directly MTD layer has originated
in OpenWrt some time ago and supports already about 497 use cases in 357
device tree files.

Cc: Alban Bedel <albeu@free.fr>
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: John Crispin <john@phrozen.org>
Signed-off-by: Petr Štetiar <redacted>
---

 Changes since v1:

  * moved handling of nvmem after mac-address and local-mac-address properties

 Changes since v2:

  * moved of_get_mac_addr_nvmem after of_get_mac_addr(np, "address") call
  * replaced kzalloc, kmemdup and kfree with it's devm variants
  * introduced of_has_nvmem_mac_addr helper which checks if DT node has nvmem
    cell with `mac-address`
  * of_get_mac_address now returns ERR_PTR encoded error value

 Changes since v3:

  * removed of_has_nvmem_mac_addr helper as it's not needed now
  * of_get_mac_address now returns only valid pointer or ERR_PTR encoded error value

 drivers/of/of_net.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 51 insertions(+), 3 deletions(-)

diff --git a/drivers/of/of_net.c b/drivers/of/of_net.c
index d820f3e..9649cd5 100644
--- a/drivers/of/of_net.c
+++ b/drivers/of/of_net.c

@@ -8,8 +8,10 @@
 #include <linux/etherdevice.h>
 #include <linux/kernel.h>
 #include <linux/of_net.h>
+#include <linux/of_platform.h>
 #include <linux/phy.h>
 #include <linux/export.h>
+#include <linux/device.h>

 /**
  * of_get_phy_mode - Get phy mode for given device_node

@@ -47,12 +49,52 @@ static const void *of_get_mac_addr(struct device_node *np, const char *name)
 	return NULL;
 }

+static const void *of_get_mac_addr_nvmem(struct device_node *np)
+{
+	int ret;
+	u8 mac[ETH_ALEN];
+	struct property *pp;
+	struct platform_device *pdev = of_find_device_by_node(np);
+
+	if (!pdev)
+		return ERR_PTR(-ENODEV);
+
+	ret = nvmem_get_mac_address(&pdev->dev, &mac);
+	if (ret)
+		return ERR_PTR(ret);
+
+	pp = devm_kzalloc(&pdev->dev, sizeof(*pp), GFP_KERNEL);
+	if (!pp)
+		return ERR_PTR(-ENOMEM);
+
+	pp->name = "nvmem-mac-address";
+	pp->length = ETH_ALEN;
+	pp->value = devm_kmemdup(&pdev->dev, mac, ETH_ALEN, GFP_KERNEL);
+	if (!pp->value) {
+		ret = -ENOMEM;
+		goto free;
+	}
+
+	ret = of_add_property(np, pp);
+	if (ret)
+		goto free;
+
+	return pp->value;