linux-kernel - Re: x86: A fast way to check capabilities of the current cpu

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Message-ID: <4D092D15.7030700@zytor.com>
Date:	Wed, 15 Dec 2010 13:03:17 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Christoph Lameter <cl@...ux.com>, Tejun Heo <tj@...nel.org>,
	Pekka Enbeerg <penberg@...helsinki.fi>,
	linux-kernel@...r.kernel.org,
	Eric Dumazet <eric.dumazet@...il.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: Re: x86: A fast way to check capabilities of the current cpu

On 12/15/2010 12:56 PM, Andrew Morton wrote:
> On Wed, 15 Dec 2010 14:07:39 -0600 (CST)
> Christoph Lameter <cl@...ux.com> wrote:
> 
>> +#define cpu_has(c, bit)							\
>> +	(__builtin_constant_p(bit) && REQUIRED_MASK_BIT_SET(bit) ? 1 :	\
>>  	 test_cpu_cap(c, bit))
>>
>> +#define this_cpu_has(bit)						\
>> +	(__builtin_constant_p(bit) && REQUIRED_MASK_BIT_SET(bit) ? 1 : 	\
>> +	 this_cpu_test_bit(bit, (unsigned long *)&cpu_info.x86_capability))
>> +
> 
> Isn't
> 
> 	a ? 1 : b
> 
> a complex way of writing
> 
> 	a || b
> 

Not if b is not a bool.

	-hpa

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