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SubjectRe: [PATCH] fixed pcnet32 multicast listen on big endian
On Wed, 26 Feb 2003, Jeff Garzik wrote:
> Geert Uytterhoeven wrote:
> > On Sun, 23 Feb 2003, Geert Uytterhoeven wrote:
> >>On Wed, 5 Feb 2003, Marcus Meissner wrote:
> >>>This fixes multicast listen for pcnet32 on at least powerpc and powerpc64
> >>>kernels.
> >>>
> >>>The mcast_table is in memory referenced by the card and so it needs
> >>>to be accessed in little endian mode.
> >>>
> >>>Ciao, Marcus
> >>>
> >>>--- linux-2.4.19/drivers/net/pcnet32.c.be 2003-02-05 07:59:27.000000000 +0100
> >>>+++ linux-2.4.19/drivers/net/pcnet32.c 2003-02-05 08:00:22.000000000 +0100
> >>>@@ -1534,7 +1534,9 @@
> >>>
> >>> crc = ether_crc_le(6, addrs);
> >>> crc = crc >> 26;
> >>>- mcast_table [crc >> 4] |= 1 << (crc & 0xf);
> >>>+ mcast_table [crc >> 4] = le16_to_cpu(
> >>
> >> ^^^^^^^^^^^
> >>
> >>>+ le16_to_cpu(mcast_table [crc >> 4]) | (1 << (crc & 0xf))
> >>>+ );
> >>
> >>Shouldn't the first conversion be `cpu_to_le16'?
> >
> >
> > Ugh, a quick grep shows that this driver _always_ uses `le*_to_cpu()' to
> > convert from CPU to little endian.
>
> Cosmetically you are correct, and I prefer it to be changed eventually.
>
> However programatically, it has no effect, because those cpu_to_foo and
> foo_to_cpu functions either swap, or they don't. Direction doesn't
> matter terribly much :)

That's true.

BTW, you save one swap by changing the code to

mcast_table [crc >> 4] |= cpu_to_le16(1 << (crc & 0xf));

Because the order of bitwise or and swap doesn't matter.

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds

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