Re: [PATCH] ARM: kirkwood: add missing <linux/if_ether.h> for ETH_ALEN

[Daniel Golle]

Hi Andrew,

On Sat, Aug 07, 2021 at 04:17:44PM +0200, Andrew Lunn wrote:
> > What kernel is this? I've just tested with this exact commit as
> > base and it compiles just fine.
> > 
> > I'm not saying including the file is wrong, but it seems it isn't
> > needed in the upstream kernel and I don't know if it qualifies for
> > the stable queue therefore.
> 
> I would like to see a reproducer for mainline. Do you have a kernel
> config which generates the problem.

I encountered the problem when building the 'kirkwood' target in
OpenWrt. I have now tried building vanilla, and the problem indeed
doesn't exist. After tracing the header includes with the precompiler
for some time I concluded that <linux/of_net.h> included in kirkwood.c
includes <linux/phy.h> which includes <linux/ethtool.h> which includes
<uapi/linux/ethtool.h> which includes <uapi/linux/if_ether.h> which
includes <linux/if_ether.h> which defined ETH_ALEN.

When building OpenWrt kernel which includes a backport of
"of: net: pass the dst buffer to of_get_mac_address()", this is not the
same as <linux/of_net.h> doesn't include <linux/phy.h> yet. This is
because we miss commit 0c65b2b90d13c1 ("net: of_get_phy_mode: Change
API to solve int/unit warnings") which has been in mainline for a long
time.

> The change itself does seems reasonable, so if we can reproduce it, i
> would be happy to merge it for stable.

Sorry for the noise caused, I'm not sure what the policy is in this
case, but certainly this is *not* a regression which should make it to
stable asap. The long and confusing chain of includes which lead to the
ETH_ALEN macro being defined in arch/arm/mach-mvebu/kirkwood.c is
certainly not ideal, and in case you still consider this patch worth
merging, I will post v2 with re-written commit description.