Re: [PATCH V2 3/3] ethernet: Convert mac address uses of 6 toETH_ALEN

[Russell King - ARM Linux]

On Thu, Aug 01, 2013 at 01:55:28PM -0700, Joe Perches wrote:
> On Thu, 2013-08-01 at 21:33 +0100, Russell King - ARM Linux wrote:
> > On Thu, Aug 01, 2013 at 01:31:09PM -0700, Olof Johansson wrote:
> > > Hi,
> 
> Hi all.
> 
> > > On Thu, Aug 1, 2013 at 1:14 PM, Joe Perches <joe@xxxxxxxxxxx> wrote:
> > > > diff --git a/drivers/net/ethernet/pasemi/pasemi_mac.h b/drivers/net/ethernet/pasemi/pasemi_mac.h
> []
> > > > @@ -79,11 +79,11 @@ struct pasemi_mac {
> > > >         int             last_cs;
> > > >         int             num_cs;
> > > >         u32             dma_if;
> > > > -       u8              type;
> > > >  #define MAC_TYPE_GMAC  1
> > > >  #define MAC_TYPE_XAUI  2
> > > >
> > > > -       u8              mac_addr[6];
> > > > +       u8              mac_addr[ETH_ALEN];
> > > > +       u8              type;
> > > 
> > > Just promote 'type' to u32 instead, saves you from moving the #defines
> > > down, etc, etc.
> 
> type is already u8, why change it?
> That would also change struct size.
> 
> > There's a more fundamental question which has to be asked: what is the
> > point of moving that in the first place?
> 
> Some is_<foo>_ether_addr tests assume __aligned(2)
> by a casting char * to u16/be16 * and dereferencing.
> 
> see patch 0/3 and include/linux/etherdevice.h

This seems rather obscure - I mean, it's not obvious to driver authors
that should be the case.  Would it not be better to make this a little
more obvious somehow?  Maybe __aligned(2) against mac_addr?  Or
maybe have a debugging check for it?
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