From: Ralf Baechle <ralf@linux-mips.org>
To: David Laight <David.Laight@ACULAB.COM>
Cc: David Daney <ddaney.cavm@gmail.com>,
netdev@vger.kernel.org, "David S. Miller" <davem@davemloft.net>,
linux-mips@linux-mips.org, David Daney <david.daney@cavium.com>
Subject: Re: [PATCH 2/2] netdev: octeon_mgmt: Fix structure layout for little-endian.
Date: Thu, 27 Jun 2013 12:40:48 +0200 [thread overview]
Message-ID: <20130627104048.GR7171@linux-mips.org> (raw)
In-Reply-To: <AE90C24D6B3A694183C094C60CF0A2F6026B729B@saturn3.aculab.com>
On Thu, Jun 20, 2013 at 10:47:57AM +0100, David Laight wrote:
> > The C ABI reverses the bitfield fill order when compiled as
> > little-endian.
>
> No - it is completely implementation defined.
> The general concensus is not to use bitfields if you
> care at all about the bit assignments.
FWIW, bitfields often alow things to be expressed more nicely. Just the
endian-dependent definition suck, so I came up with this little hack
for arch/mips/include/uapi/asm/inst.h:
#ifdef __MIPSEB__
#define BITFIELD_FIELD(field, more) \
field; \
more
#elif defined(__MIPSEL__)
#define BITFIELD_FIELD(field, more) \
more \
field;
#endif
struct i_format { /* signed immediate format */
BITFIELD_FIELD(unsigned int opcode : 6,
BITFIELD_FIELD(unsigned int rs : 5,
BITFIELD_FIELD(unsigned int rt : 5,
BITFIELD_FIELD(signed int simmediate : 16,
;))))
};
Ralf
next prev parent reply other threads:[~2013-06-27 10:41 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-06-20 0:40 [PATCH 0/2] netdev: octeon_mgmt minor fixes David Daney
2013-06-20 0:40 ` [PATCH 1/2] netdev: octeon_mgmt: Correct tx IFG workaround David Daney
2013-06-20 1:08 ` Joe Perches
2013-06-20 1:28 ` David Daney
2013-06-20 1:37 ` Joe Perches
2013-06-20 1:47 ` David Daney
2013-06-20 0:40 ` [PATCH 2/2] netdev: octeon_mgmt: Fix structure layout for little-endian David Daney
2013-06-20 9:47 ` David Laight
2013-06-27 10:40 ` Ralf Baechle [this message]
2013-06-20 5:13 ` [PATCH 0/2] netdev: octeon_mgmt minor fixes David Miller
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