linux-kernel - Re: [PATCH 2/5] irqchip/gic-v3: Make gic_enable

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Message-ID: <20151008155404.GN17192@e104818-lin.cambridge.arm.com>
Date:	Thu, 8 Oct 2015 16:54:04 +0100
From:	Catalin Marinas <catalin.marinas@....com>
To:	Marc Zyngier <marc.zyngier@....com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Jason Cooper <jason@...edaemon.net>,
	Will Deacon <will.deacon@....com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 2/5] irqchip/gic-v3: Make gic_enable_sre an inline
 function

On Fri, Oct 02, 2015 at 05:37:51PM +0100, Marc Zyngier wrote:
> +static inline bool gic_enable_sre(void)
> +{
> +	u64 val;
> +
> +	asm volatile("mrs_s %0, " __stringify(ICC_SRE_EL1) : "=r" (val));
> +	if (val & ICC_SRE_EL1_SRE)
> +		return true;
> +
> +	val |= ICC_SRE_EL1_SRE;
> +	asm volatile("msr_s " __stringify(ICC_SRE_EL1) ", %0" : : "r" (val));
> +	isb();
> +	asm volatile("mrs_s %0, " __stringify(ICC_SRE_EL1) : "=r" (val));
> +
> +	return !!(val & ICC_SRE_EL1_SRE);
> +}

I don't think !! is needed ;). Apparently, from ISO C99: "When any
scalar value is converted to _Bool, the result is 0 if the value
compares equal to 0; otherwise, the result is 1."

-- 
Catalin
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