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SubjectRe: [PATCH] lib/vsprintf.c: Add %pMF to format FDDI bit reversed MAC addresses
On Thu, 7 Jan 2010, Joe Perches wrote:

> On Mon, 2010-01-04 at 23:43 +0000, Maciej W. Rozycki wrote:
> > The example below shows an address, and the sequence of bits or symbols
> > that would be transmitted when the address is used in the Source Address
> > or Destination Address fields on the MAC header. The transmission line
> > shows the address bits in the order transmitted, from left to right. For
> > IEEE 802 LANs these correspond to actual bits on the medium. The FDDI
> > symbols line shows how the FDDI PHY sends the address bits as encoded
> > symbols.
> >
> > MSB: 35:7B:12:00:00:01
> > Canonical: AC-DE-48-00-00-80
> > Transmission: 00110101 01111011 00010010 00000000 00000000 00000001
> > FDDI Symbols: 35 7B 12 00 00 01"
> >
> > Please note that this address has its group bit clear.
> >
> > This notation is also defined in the "FDDI MEDIA ACCESS CONTROL-2
> > (MAC-2)" (X3T9/92-120) document although that book does not have a need
> > to use the MSB form and it's skipped.
>
> Adds 56 bytes to object size
>
> New:
> $ size lib/vsprintf.o
> text data bss dec hex filename
> 8714 0 2 8716 220c lib/vsprintf.o
> old:
> $ size lib/vsprintf.o
> text data bss dec hex filename
> 8658 0 2 8660 21d4 lib/vsprintf.o

What's the gain? I'd be rather conservative when taking everybody's 56
bytes for one or two drivers hardly anybody uses. The format of MAC
addresses is unlikely to change, so I'd say the sources can live with
one or two places where the strings are formatted manually. Even if the
drivers lose more than these 56 bytes.

Maciej


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