Subject: using IS_ENABLED(CONFIG_xyz) effectively
To: Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        Paul Gortmaker <paul.gortmaker@windriver.com>,
        Ingo Molnar <mingo@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>, "H. Peter Anvin" <hpa@zytor.com>,
        Michal Marek <mmarek@suse.cz>
References: <5613F3DE.4010406@suse.cz>
 <1444165543-2209-1-git-send-email-linux@rasmusvillemoes.dk>
CC: "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>,
        arcml <linux-snps-arc@lists.infradead.org>
From: Vineet Gupta <Vineet.Gupta1@synopsys.com>
Message-ID: <56498D0A.3070000@synopsys.com>
Date: Mon, 16 Nov 2015 13:30:10 +0530
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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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