Re: [PATCH 5/8] net: add helper eth_addr_add()

[Michael Walle]

Am 2022-01-25 11:24, schrieb Rafał Miłecki:
> On 28.12.2021 15:25, Michael Walle wrote:
> > Add a helper to add an offset to a ethernet address. This comes in 
> > handy
> > if you have a base ethernet address for multiple interfaces.
> >
> > Signed-off-by: Michael Walle <michael@xxxxxxxx>
> > ---
> >   include/linux/etherdevice.h | 14 ++++++++++++++
> >   1 file changed, 14 insertions(+)
> >
> > diff --git a/include/linux/etherdevice.h b/include/linux/etherdevice.h
> > index 2ad71cc90b37..9d621dc85290 100644
> > --- a/include/linux/etherdevice.h
> > +++ b/include/linux/etherdevice.h
> > @@ -486,6 +486,20 @@ static inline void eth_addr_inc(u8 *addr)
> >   	u64_to_ether_addr(u, addr);
> >   }
> >   +/**
> > + * eth_addr_add() - Add (or subtract) and offset to/from the given 
> > MAC address.
> > + *
> > + * @offset: Offset to add.
> > + * @addr: Pointer to a six-byte array containing Ethernet address to 
> > increment.
> > + */
> > +static inline void eth_addr_add(u8 *addr, long offset)
> > +{
> > +	u64 u = ether_addr_to_u64(addr);
> > +
> > +	u += offset;
> > +	u64_to_ether_addr(u, addr);
> > +}
>
> Please check eth_hw_addr_gen() which contains identical code +
> eth_hw_addr_set().
>
> You should probably make eth_hw_addr_gen() use your new function as a
> helper.

You'd need to copy the mac address first because eth_addr_add()
modifies the mac address in place. I don't see that this is
improving anything.

-michael