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>

2 files changed, 8 insertions, 9 deletions

diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
index 1409ae986aa2..8c84c40ab9a0 100644
--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c
@@ -109,11 +109,13 @@ static void ravb_set_buffer_align(struct sk_buff *skb)
  * Ethernet AVB device doesn't have ROM for MAC address.
  * This function gets the MAC address that was used by a bootloader.
  */
-static void ravb_read_mac_address(struct net_device *ndev, const u8 *mac)
+static void ravb_read_mac_address(struct device_node *np,
+				  struct net_device *ndev)
 {
-	if (!IS_ERR(mac)) {
-		ether_addr_copy(ndev->dev_addr, mac);
-	} else {
+	int ret;
+
+	ret = of_get_mac_address(np, ndev->dev_addr);
+	if (ret) {
 		u32 mahr = ravb_read(ndev, MAHR);
 		u32 malr = ravb_read(ndev, MALR);
 
@@ -2207,7 +2209,7 @@ static int ravb_probe(struct platform_device *pdev)
 	priv->msg_enable = RAVB_DEF_MSG_ENABLE;
 
 	/* Read and set MAC address */
-	ravb_read_mac_address(ndev, of_get_mac_address(np));
+	ravb_read_mac_address(np, ndev);
 	if (!is_valid_ether_addr(ndev->dev_addr)) {
 		dev_warn(&pdev->dev,
 			 "no valid MAC address supplied, using a random one\n");
diff --git a/drivers/net/ethernet/renesas/sh_eth.c b/drivers/net/ethernet/renesas/sh_eth.c
index ebedb1a11132..c5b154868c1f 100644
--- a/drivers/net/ethernet/renesas/sh_eth.c
+++ b/drivers/net/ethernet/renesas/sh_eth.c
@@ -3170,7 +3170,6 @@ static struct sh_eth_plat_data *sh_eth_parse_dt(struct device *dev)
 	struct device_node *np = dev->of_node;
 	struct sh_eth_plat_data *pdata;
 	phy_interface_t interface;
-	const char *mac_addr;
 	int ret;
 
 	pdata = devm_kzalloc(dev, sizeof(*pdata), GFP_KERNEL);
@@ -3182,9 +3181,7 @@ static struct sh_eth_plat_data *sh_eth_parse_dt(struct device *dev)
 		return NULL;
 	pdata->phy_interface = interface;
 
-	mac_addr = of_get_mac_address(np);
-	if (!IS_ERR(mac_addr))
-		ether_addr_copy(pdata->mac_addr, mac_addr);
+	of_get_mac_address(np, pdata->mac_addr);
 
 	pdata->no_ether_link =
 		of_property_read_bool(np, "renesas,no-ether-link");