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Date: Sun, 23 Mar 2014 22:30:47 -0700 From: Guenter Roeck <linux@...ck-us.net> To: Joe Perches <joe@...ches.com> CC: linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org, Zhang Rui <rui.zhang@...el.com>, Eduardo Valentin <eduardo.valentin@...com> Subject: Re: [PATCH] thermal: Fix KELVIN_TO_CELSIUS macro On 03/23/2014 09:25 PM, Joe Perches wrote: > On Sun, 2014-03-23 at 21:14 -0700, Guenter Roeck wrote: >> It is always a good idea to use paranthesis around macro parameters >> to avoid undesired side effects. >> >> In this specific case, KELVIN_TO_CELSIUS() is used in >> drivers/platform/x86/asus-wmi.c with parameter "value & 0xFFFF", >> which due to operator evaluation order causes more or less random >> results. > > Maybe it's better to use a statement expression to avoid > multiple calculations of t > > Maybe; > > #define KELVIN_TO_CELSIUS(t) \ > ({ \ > long _t = (long)(t) - 2732; \ > _t >= 0 ? (_t + 5) / 10 : (_t - 5) / 10; \ > }) > > Possibly, but I only want to have a bug fixed which should possibly be applied to -stable at some point. As such, I prefer the minimalistic approach. Anything more fancy on top of that can be submitted as separate patch. Guenter -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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