2018-07-19 10:48 GMT+02:00 Dan Carpenter [off-list ref]:

On Thu, Jul 19, 2018 at 10:20:27AM +0200, Bartosz Golaszewski wrote:

quoted

From: Bartosz Golaszewski <redacted>

Many non-DT platforms read the MAC address from EEPROM. Usually it's
either done with callbacks defined in board files or from SoC-specific
ethernet drivers.

In order to generalize this, try to read the MAC from nvmem in
eth_platform_get_mac_address() using a standard lookup name:
"mac-address".

Signed-off-by: Bartosz Golaszewski <redacted>
---
 net/ethernet/eth.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c
index 39af03894598..af3b4b1b77eb 100644
--- a/net/ethernet/eth.c
+++ b/net/ethernet/eth.c

@@ -54,6 +54,7 @@
 #include <linux/if_ether.h>
 #include <linux/of_net.h>
 #include <linux/pci.h>
+#include <linux/nvmem-consumer.h>
 #include <net/dst.h>
 #include <net/arp.h>
 #include <net/sock.h>

@@ -527,8 +528,11 @@ unsigned char * __weak arch_get_platform_mac_address(void)

 int eth_platform_get_mac_address(struct device *dev, u8 *mac_addr)
 {
+     unsigned char addrbuf[ETH_ALEN];
      const unsigned char *addr;
+     struct nvmem_cell *nvmem;
      struct device_node *dp;
+     size_t alen;

      if (dev_is_pci(dev))
              dp = pci_device_to_OF_node(to_pci_dev(dev));

@@ -541,6 +545,29 @@ int eth_platform_get_mac_address(struct device *dev, u8 *mac_addr)
      if (!addr)
              addr = arch_get_platform_mac_address();

+     if (!addr) {
+             nvmem = nvmem_cell_get(dev, "mac-address");
+             if (IS_ERR(nvmem) && 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)) {
+                     addr = nvmem_cell_read(nvmem, &alen);
+                     if (!IS_ERR(addr)) {

                                    ^^^^
Never do success handling.  Always error handling.  Otherwise the code
is indent a lot and the error handling is far from the call.

quoted

+                             if (alen == ETH_ALEN)
+                                     ether_addr_copy(addrbuf, addr);
+
+                             kfree(addr);
+                             addr = alen == ETH_ALEN ? addrbuf : NULL;
+                     }
+
+                     nvmem_cell_put(nvmem);
+             }
+     }
+
      if (!addr || !is_valid_ether_addr(addr))

                                          ^^^^
Instead of handling the error we dereference the error pointer here.

True - we should add a check for IS_ERR(addr) here.

*frowny face*

quoted

              return -ENODEV;

--

Maybe this?

        if (!addr) {
                nvmem = nvmem_cell_get(dev, "mac-address");
                if (PTR_ERR(nvmem) == -EPROBE_DEFER)
                        return -EPROBE_DEFER;
                if (IS_ERR(nvmem))
                        return -ENODEV;
                addr = nvmem_cell_read(nvmem, &alen);
                if (IS_ERR(addr))
                        return PTR_ERR(addr);
                if (alen != ETH_ALEN) {
                        kfree(addr);
                        return -ENODEV;
                }
                ether_addr_copy(addrbuf, addr);
                kfree(addr);
                addr = addrbuf;
        }
        if (!is_valid_ether_addr(addr))
                return -ENODEV;
        ether_addr_copy(mac_addr, addr);
        return 0;

I would normally go this way but here we don't want to bail out when
we encounter an error but rather continue on to the next possible
source of a MAC address. We'll get -ENODEV from nvmem_cell_get() if
the lookup fails for "mac-address" but instead of returning an error
code we should then check if we can read the MAC from MTD.

Bart