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

From: Joe Perches <joe@perches.com>
Date: Wed, 06 Jan 2016 15:32:24 -0800

On Thu, 2016-01-07 at 00:26 +0100, Bjørn Mork wrote:

quoted

Joe Perches [off-list ref] writes:

quoted

On Wed, 2016-01-06 at 16:33 -0500, David Miller wrote:

quoted

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.

[]

quoted

diff --git a/include/linux/etherdevice.h b/include/linux/etherdevice.h

[]

quoted

@@ -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 ?

That would prevent a driver from using this with additional fallback
methods.  For what reason?

It's declared __weak and should be overridden by
an arch specific function.

A NULL address would cause a fault when using
a function like copy_ether_addr.

The caller checks for NULL, and this is the default implementation
doing precisely what it is meant to do.