linux-kernel - Re: [PATCH 2/5] Blackfin arch: SMP supporting patchset: Blackfin header files and machine common code

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Date:	Thu, 20 Nov 2008 08:50:50 -0500
From:	"Mike Frysinger" <vapier.adi@...il.com>
To:	"Bryan Wu" <cooloney@...nel.org>
Cc:	"Andrew Morton" <akpm@...ux-foundation.org>,
	torvalds@...ux-foundation.org, mingo@...e.hu,
	linux-kernel@...r.kernel.org, "Graf Yang" <graf.yang@...log.com>
Subject: Re: [PATCH 2/5] Blackfin arch: SMP supporting patchset: Blackfin header files and machine common code

On Wed, Nov 19, 2008 at 02:42, Bryan Wu wrote:
> On Wed, Nov 19, 2008 at 2:56 PM, Andrew Morton wrote:
>> On Tue, 18 Nov 2008 17:05:05 +0800 Bryan Wu wrote:
>>> From: Graf Yang <graf.yang@...log.com>
>>> +#define smp_mb__before_clear_bit()   barrier()
>>> +#define smp_mb__after_clear_bit()    barrier()
>>> +
>>> +static inline void __set_bit(int nr, volatile unsigned long *addr)
>>> +{
>>> +     int *a = (int *)addr;
>>> +     int mask;
>>> +
>>> +     a += nr >> 5;
>>> +     mask = 1 << (nr & 0x1f);
>>> +     *a |= mask;
>>> +}
>>> +
>>> +static inline void __clear_bit(int nr, volatile unsigned long *addr)
>>> +{
>>> +     int *a = (int *)addr;
>>> +     int mask;
>>> +
>>> +     a += nr >> 5;
>>> +     mask = 1 << (nr & 0x1f);
>>> +     *a &= ~mask;
>>> +}
>>> +
>>> +static inline void __change_bit(int nr, volatile unsigned long *addr)
>>> +{
>>> +     int mask;
>>> +     unsigned long *ADDR = (unsigned long *)addr;
>>> +
>>> +     ADDR += nr >> 5;
>>> +     mask = 1 << (nr & 31);
>>> +     *ADDR ^= mask;
>>> +}
>>
>> I'm surprised there isn't any generic code which can be used for the above.
>>
>
> As Nick said, include/asm-generic/bitops/non-atomic.h is the generic code.
> We will try it.

the Blackfin ISA provides explicit bit operations.  is there something
special about these C-level bit operations that prevents us from using
them ?

PRM:
"BITCLR" on page 13-2
"BITSET" on page 13-4
"BITTGL" on page 13-6
-mike
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