Subject: Re: [PATCH v2] net: Add eth_platform_get_mac_address() helper.

From: Joe Perches <[email-masked]>
Date: Wed, 06 Jan 2016 15:12:46 -0800

On Wed, 2016-01-06 at 16:33 -0500, David Miller wrote:
> A repeating pattern in drivers has become to use OF node information
> and, if not found, platform specific host information to extract the
> ethernet address for a given device.
[]
> diff --git a/include/linux/etherdevice.h b/include/linux/etherdevice.h
[]
> @@ -485,3 +487,32 @@ static int __init eth_offload_init(void)
>  }
>  
>  fs_initcall(eth_offload_init);
> +
> +unsigned char * __weak arch_get_platform_mac_address(void)
> +{
> +       return NULL;

WARN_ON_ONCE ?

> +}
> +
> +int eth_platform_get_mac_address(struct device *dev, u8 *mac_addr)
> +{
> +       const unsigned char *addr;
> +       struct device_node *dp;
> +
> +       if (dev_is_pci(dev))
> +               dp = pci_device_to_OF_node(to_pci_dev(dev));
> +       else
> +               dp = dev->of_node;
> +
> +       addr = NULL;
> +       if (dp)
> +               addr = of_get_mac_address(dp);
> +       if (!addr)
> +               addr = arch_get_platform_mac_address();
> +
> +       if (!addr)
> +               return -ENODEV;
> +
> +       ether_addr_copy(mac_addr, addr);

Couldn't some oddball arch have an unaligned addr?