Messages in this thread Patch in this message | | | Subject | Re: [PATCH v3] ARM: pxa: fix GPIO double shifts | From | Joe Perches <> | Date | Sun, 31 Jul 2016 13:44:42 -0700 |
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On Sun, 2016-07-31 at 14:17 +0200, Robert Jarzmik wrote: > The commit 9bf448c66d4b ("ARM: pxa: use generic gpio operation instead of > gpio register") from Oct 17, 2011, leads to the following static checker > warning: > arch/arm/mach-pxa/spitz_pm.c:172 spitz_charger_wakeup() > warn: double left shift '!gpio_get_value(SPITZ_GPIO_KEY_INT) > << (1 << ((SPITZ_GPIO_KEY_INT) & 31))' > > As Dan reported, the value is shifted three times : > - once by gpio_get_value(), which returns either 0 or BIT(gpio) > - once by the shift operation '<<' > - a last time by GPIO_bit(gpio) which is BIT(gpio) > > Therefore the calculation lead to a chained or operator of : > - (1 << gpio) << (1 << gpio) = (2^gpio)^gpio = 2 ^ (gpio * gpio) > > It is be sheer luck the former statement works, only because each gpio > used is strictly smaller than 6, and therefore 2^(gpio^2) never > overflows a 32 bits value, and because it is used as a boolean value to > check a gpio activation. > > As the xxx_charger_wakeup() functions are used as a true/false detection > mechanism, take that opportunity to change their prototypes from integer > return value to boolean one. > > Fixes: 9bf448c66d4b ("ARM: pxa: use generic gpio operation instead of > gpio register") > Reported-by: Dan Carpenter <dan.carpenter@oracle.com> > Cc: Joe Perches <joe@perches.com> > Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr> > --- > Since v1: replaced binary ORs with logical ORs after assembly comparison > Since v2: changed charger_wakeup prototype to bool foo()
Thanks Robert
trivially: > diff --git a/arch/arm/mach-pxa/corgi_pm.c b/arch/arm/mach-pxa/corgi_pm.c [] > @@ -131,15 +131,13 @@ static int corgi_should_wakeup(unsigned int resume_on_alarm) > return is_resume; > } > > -static unsigned long corgi_charger_wakeup(void) > +static bool corgi_charger_wakeup(void) > { > - unsigned long ret; > + bool ret; > > - ret = (!gpio_get_value(CORGI_GPIO_AC_IN) << GPIO_bit(CORGI_GPIO_AC_IN)) > - | (!gpio_get_value(CORGI_GPIO_KEY_INT) > - << GPIO_bit(CORGI_GPIO_KEY_INT)) > - | (!gpio_get_value(CORGI_GPIO_WAKEUP) > - << GPIO_bit(CORGI_GPIO_WAKEUP)); > + ret = !gpio_get_value(CORGI_GPIO_AC_IN) > + || !gpio_get_value(CORGI_GPIO_KEY_INT) > + || !gpio_get_value(CORGI_GPIO_WAKEUP);
These might be better without the automatic use of ret
return !gpio_get_value(CORGI_GPIO_AC_IN) || !gpio_get_value(CORGI_GPIO_KEY_INT) || !gpio_get_value(CORGI_GPIO_WAKEUP);
and
> diff --git a/arch/arm/mach-pxa /spitz_pm.c b/arch/arm/mach-pxa/spitz_pm.c [] > @@ -165,12 +165,12 @@ static int spitz_should_wakeup(unsigned int resume_on_alarm) > return is_resume; > } > > -static unsigned long spitz_charger_wakeup(void) > +static bool spitz_charger_wakeup(void) > { > - unsigned long ret; > - ret = ((!gpio_get_value(SPITZ_GPIO_KEY_INT) > - << GPIO_bit(SPITZ_GPIO_KEY_INT)) > - | gpio_get_value(SPITZ_GPIO_SYNC)); > + bool ret; > + > + ret = !gpio_get_value(SPITZ_GPIO_KEY_INT) > + || gpio_get_value(SPITZ_GPIO_SYNC); > return ret; > }
return !gpio_get_value(SPITZ_GPIO_KEY_INT) || gpio_get_value(SPITZ_GPIO_SYNC);
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