linux-kernel - using IS_ENABLED(CONFIG

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Message-ID: <56498D0A.3070000@synopsys.com>
Date:	Mon, 16 Nov 2015 13:30:10 +0530
From:	Vineet Gupta <Vineet.Gupta1@...opsys.com>
To:	Rasmus Villemoes <linux@...musvillemoes.dk>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Ingo Molnar <mingo@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, Michal Marek <mmarek@...e.cz>
CC:	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>,
	arcml <linux-snps-arc@...ts.infradead.org>
Subject: using IS_ENABLED(CONFIG_xyz) effectively

Hi,

I've been using IS_ENABLED for some time and once in a while run into an issue
which prevents seamless use. Hence posing this question to experts in the area.

C macro processor evaluates the ensuing control block even if IS_ENABLED evaluates
to false. This requires dummy #defines or worse still removing usage of IS_ENABLED
altogether.

e.g. In example below even for ARCOMPACT builds, we need the ARCV2 specific define
ARCV2_IRQ_DEF_PRIO.

void arch_cpu_idle(void)
{
        if (is_isa_arcompact()) {    <---- IS_ENABLED(CONFIG_ISA_ARCOMPACT)
                __asm__("sleep 0x3");
        } else {
		const int arg = 0x10 | ARCV2_IRQ_DEF_PRIO;
               __asm__("sleep 0x10");
	}
}

One could argue that the interface needs to be cleanly defined to not have such
specific #defines in common code in first place. However sometime that becomes
just too tedious.

Is there a way to get around by this ?

Thx,
-Vineet
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