2018-07-19 17:22 GMT+02:00 Andrew Lunn [off-list ref]:

On Wed, Jul 18, 2018 at 06:10:34PM +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 | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c
index 6b64586fd2af..adf5bd03851f 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>

@@ -530,7 +531,10 @@ int eth_platform_get_mac_address(struct device *dev, u8 *mac_addr)
      struct device_node *dp = dev_is_pci(dev) ?
                      pci_device_to_OF_node(to_pci_dev(dev)) : dev->of_node;
      const unsigned char *addr = NULL;
+     unsigned char addrbuf[ETH_ALEN];
+     struct nvmem_cell *nvmem;
      const char *from = NULL;
+     size_t alen;

      if (dp) {
              addr = of_get_mac_address(dp);

@@ -544,6 +548,31 @@ int eth_platform_get_mac_address(struct device *dev, u8 *mac_addr)
                      from = "arch callback";
      }

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

How does EPROBE_DEFER work here? You say the use case is
Non-DT. Without having DT, how do you know the cell should exist, but
does not yet exist? I might be looking at old code, but i only see
-EPROBE_DEFER inside the if (np) case.

quoted

+                     /* We may have a lookup registered for MAC address but
+                      * the corresponding nvmem provider hasn't been
+                      * registered yet.
+                      */
+                     return -EPROBE_DEFER;

You really should return real errors. If i'm reading
__nvmem_device_get() right, it will return a NULL pointer when the
cell does not exist. NULL is not an error, so IS_ERR() will return
false. So you should return all errors from nvmem_cell_get().

       Andrew

We have a patch queued for nvmem for 4.19 which adds a notion of nvmem
cell lookups similar to gpio lookups:
https://patchwork.kernel.org/patch/10496045/

This will work fine with probe deferral.

Bart