From: Geert Uytterhoeven <geert@linux-m68k.org>
To: "D.J. Barrow" <barrow_dj@yahoo.com>
Cc: linuxppc-dev <linuxppc-dev@lists.linuxppc.org>
Subject: Re: Help with cross-endian bitfields?
Date: Mon, 8 May 2000 16:19:59 +0200 (CEST) [thread overview]
Message-ID: <Pine.LNX.4.10.10005081618471.1144-100000@cassiopeia.home> (raw)
In-Reply-To: <20000508101331.16264.qmail@web204.mail.yahoo.com>
On Mon, 8 May 2000, D.J. Barrow wrote:
> struct blah
> {
> unsigned a : 3;
> unsigned b : 3;
> unsigned c : 2;
> } __attribute__(packed);
>
> I personally would be expecting to use ((*((u8
> *)&blah[0]))&0x0e0)>>5 to get the info from blah.a on
> both little & big endian machines.
Which no longer works if a is longer than 8 bits and/or spans multiple bytes.
For PCI accesses, you can work around this by using {read,write}l(), which do
byte swapping on big-endian platforms as well.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- Linux/{m68k~Amiga,PPC~CHRP} -- 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
** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/
next prev parent reply other threads:[~2000-05-08 14:19 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2000-05-08 10:13 Help with cross-endian bitfields? D.J. Barrow
2000-05-08 14:19 ` Geert Uytterhoeven [this message]
-- strict thread matches above, loose matches on Subject: below --
2000-05-08 14:38 jlquinn
[not found] <200005060514.AAA05188@lists.linuxppc.org>
2000-05-08 7:03 ` james woodyatt
2000-05-08 9:50 ` Geert Uytterhoeven
2000-05-05 20:47 jlquinn
2000-05-05 19:27 jlquinn
2000-05-05 20:05 ` Dan Malek
2000-05-05 20:45 ` Josh Huber
2000-05-05 20:49 ` Daniel Jacobowitz
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