of: net: pass the dst buffer to of_get_mac_address()

of_get_mac_address() returns a "const void*" pointer to a MAC address.
Lately, support to fetch the MAC address by an NVMEM provider was added.
But this will only work with platform devices. It will not work with
PCI devices (e.g. of an integrated root complex) and esp. not with DSA
ports.

There is an of_* variant of the nvmem binding which works without
devices. The returned data of a nvmem_cell_read() has to be freed after
use. On the other hand the return of_get_mac_address() points to some
static data without a lifetime. The trick for now, was to allocate a
device resource managed buffer which is then returned. This will only
work if we have an actual device.

Change it, so that the caller of of_get_mac_address() has to supply a
buffer where the MAC address is written to. Unfortunately, this will
touch all drivers which use the of_get_mac_address().

Usually the code looks like:

  const char *addr;
  addr = of_get_mac_address(np);
  if (!IS_ERR(addr))
    ether_addr_copy(ndev->dev_addr, addr);

This can then be simply rewritten as:

  of_get_mac_address(np, ndev->dev_addr);

Sometimes is_valid_ether_addr() is used to test the MAC address.
of_get_mac_address() already makes sure, it just returns a valid MAC
address. Thus we can just test its return code. But we have to be
careful if there are still other sources for the MAC address before the
of_get_mac_address(). In this case we have to keep the
is_valid_ether_addr() call.

The following coccinelle patch was used to convert common cases to the
new style. Afterwards, I've manually gone over the drivers and fixed the
return code variable: either used a new one or if one was already
available use that. Mansour Moufid, thanks for that coccinelle patch!

<spml>
@a@
identifier x;
expression y, z;
@@
- x = of_get_mac_address(y);
+ x = of_get_mac_address(y, z);
  <...
- ether_addr_copy(z, x);
  ...>

@@
identifier a.x;
@@
- if (<+... x ...+>) {}

@@
identifier a.x;
@@
  if (<+... x ...+>) {
      ...
  }
- else {}

@@
identifier a.x;
expression e;
@@
- if (<+... x ...+>@e)
-     {}
- else
+ if (!(e))
      {...}

@@
expression x, y, z;
@@
- x = of_get_mac_address(y, z);
+ of_get_mac_address(y, z);
  ... when != x
</spml>

All drivers, except drivers/net/ethernet/aeroflex/greth.c, were
compile-time tested.

Suggested-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Michael Walle <michael@walle.cc>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 28 insertions, 32 deletions

diff --git a/drivers/of/of_net.c b/drivers/of/of_net.c
index bc0a27de69d4..cb77b774bf76 100644
--- a/drivers/of/of_net.c
+++ b/drivers/of/of_net.c
@@ -45,42 +45,35 @@ int of_get_phy_mode(struct device_node *np, phy_interface_t *interface)
 }
 EXPORT_SYMBOL_GPL(of_get_phy_mode);
 
-static const void *of_get_mac_addr(struct device_node *np, const char *name)
+static int of_get_mac_addr(struct device_node *np, const char *name, u8 *addr)
 {
 	struct property *pp = of_find_property(np, name, NULL);
 
-	if (pp && pp->length == ETH_ALEN && is_valid_ether_addr(pp->value))
-		return pp->value;
-	return NULL;
+	if (pp && pp->length == ETH_ALEN && is_valid_ether_addr(pp->value)) {
+		memcpy(addr, pp->value, ETH_ALEN);
+		return 0;
+	}
+	return -ENODEV;
 }
 
-static const void *of_get_mac_addr_nvmem(struct device_node *np)
+static int of_get_mac_addr_nvmem(struct device_node *np, u8 *addr)
 {
-	int ret;
-	const void *mac;
-	u8 nvmem_mac[ETH_ALEN];
 	struct platform_device *pdev = of_find_device_by_node(np);
+	int ret;
 
 	if (!pdev)
-		return ERR_PTR(-ENODEV);
+		return -ENODEV;
 
-	ret = nvmem_get_mac_address(&pdev->dev, &nvmem_mac);
-	if (ret) {
-		put_device(&pdev->dev);
-		return ERR_PTR(ret);
-	}
-
-	mac = devm_kmemdup(&pdev->dev, nvmem_mac, ETH_ALEN, GFP_KERNEL);
+	ret = nvmem_get_mac_address(&pdev->dev, addr);
 	put_device(&pdev->dev);
-	if (!mac)
-		return ERR_PTR(-ENOMEM);
 
-	return mac;
+	return ret;
 }
 
 /**
  * of_get_mac_address()
  * @np:		Caller's Device Node
+ * @addr:	Pointer to a six-byte array for the result
  *
  * Search the device tree for the best MAC address to use.  'mac-address' is
  * checked first, because that is supposed to contain to "most recent" MAC
@@ -101,24 +94,27 @@ static const void *of_get_mac_addr_nvmem(struct device_node *np)
  * this case, the real MAC is in 'local-mac-address', and 'mac-address' exists
  * but is all zeros.
  *
- * Return: Will be a valid pointer on success and ERR_PTR in case of error.
+ * Return: 0 on success and errno in case of error.
 */
-const void *of_get_mac_address(struct device_node *np)
+int of_get_mac_address(struct device_node *np, u8 *addr)
 {
-	const void *addr;
+	int ret;
+
+	if (!np)
+		return -ENODEV;
 
-	addr = of_get_mac_addr(np, "mac-address");
-	if (addr)
-		return addr;
+	ret = of_get_mac_addr(np, "mac-address", addr);
+	if (!ret)
+		return 0;
 
-	addr = of_get_mac_addr(np, "local-mac-address");
-	if (addr)
-		return addr;
+	ret = of_get_mac_addr(np, "local-mac-address", addr);
+	if (!ret)
+		return 0;
 
-	addr = of_get_mac_addr(np, "address");
-	if (addr)
-		return addr;
+	ret = of_get_mac_addr(np, "address", addr);
+	if (!ret)
+		return 0;
 
-	return of_get_mac_addr_nvmem(np);
+	return of_get_mac_addr_nvmem(np, addr);
 }
 EXPORT_SYMBOL(of_get_mac_address);