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* [PATCH v3] ARM: pxa: fix GPIO double shifts
@ 2016-07-31 12:17 Robert Jarzmik
  2016-07-31 20:44 ` Joe Perches
  0 siblings, 1 reply; 4+ messages in thread
From: Robert Jarzmik @ 2016-07-31 12:17 UTC (permalink / raw)
  To: Daniel Mack, Haojian Zhuang, Robert Jarzmik, Russell King
  Cc: linux-arm-kernel, linux-kernel, Joe Perches

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()
---
 arch/arm/mach-pxa/corgi_pm.c   | 12 +++++-------
 arch/arm/mach-pxa/sharpsl_pm.c |  2 +-
 arch/arm/mach-pxa/sharpsl_pm.h |  2 +-
 arch/arm/mach-pxa/spitz_pm.c   | 10 +++++-----
 4 files changed, 12 insertions(+), 14 deletions(-)

diff --git a/arch/arm/mach-pxa/corgi_pm.c b/arch/arm/mach-pxa/corgi_pm.c
index d9206811be9b..d935de02b582 100644
--- 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);
 	return ret;
 }
 
diff --git a/arch/arm/mach-pxa/sharpsl_pm.c b/arch/arm/mach-pxa/sharpsl_pm.c
index b80eab9993c5..249b7bd5fbc4 100644
--- a/arch/arm/mach-pxa/sharpsl_pm.c
+++ b/arch/arm/mach-pxa/sharpsl_pm.c
@@ -744,7 +744,7 @@ static int sharpsl_off_charge_battery(void)
 		time = RCNR;
 		while (1) {
 			/* Check if any wakeup event had occurred */
-			if (sharpsl_pm.machinfo->charger_wakeup() != 0)
+			if (sharpsl_pm.machinfo->charger_wakeup())
 				return 0;
 			/* Check for timeout */
 			if ((RCNR - time) > SHARPSL_WAIT_CO_TIME)
diff --git a/arch/arm/mach-pxa/sharpsl_pm.h b/arch/arm/mach-pxa/sharpsl_pm.h
index 905be6755f04..fa75b6df8134 100644
--- a/arch/arm/mach-pxa/sharpsl_pm.h
+++ b/arch/arm/mach-pxa/sharpsl_pm.h
@@ -34,7 +34,7 @@ struct sharpsl_charger_machinfo {
 #define SHARPSL_STATUS_LOCK     5
 #define SHARPSL_STATUS_CHRGFULL 6
 #define SHARPSL_STATUS_FATAL    7
-	unsigned long (*charger_wakeup)(void);
+	bool (*charger_wakeup)(void);
 	int (*should_wakeup)(unsigned int resume_on_alarm);
 	void (*backlight_limit)(int);
 	int (*backlight_get_status) (void);
diff --git a/arch/arm/mach-pxa/spitz_pm.c b/arch/arm/mach-pxa/spitz_pm.c
index ea9f9034cb54..9e2902f32fc2 100644
--- 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;
 }
 
-- 
2.1.4

^ permalink raw reply related	[flat|nested] 4+ messages in thread
* Re: [PATCH v3] ARM: pxa: fix GPIO double shifts
  2016-07-31 12:17 [PATCH v3] ARM: pxa: fix GPIO double shifts Robert Jarzmik
@ 2016-07-31 20:44 ` Joe Perches
  2016-07-31 22:04   ` Robert Jarzmik
  0 siblings, 1 reply; 4+ messages in thread
From: Joe Perches @ 2016-07-31 20:44 UTC (permalink / raw)
  To: Robert Jarzmik, Daniel Mack, Haojian Zhuang, Russell King
  Cc: linux-arm-kernel, linux-kernel

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);

^ permalink raw reply	[flat|nested] 4+ messages in thread
* Re: [PATCH v3] ARM: pxa: fix GPIO double shifts
  2016-07-31 20:44 ` Joe Perches
@ 2016-07-31 22:04   ` Robert Jarzmik
  2016-07-31 22:22     ` Joe Perches
  0 siblings, 1 reply; 4+ messages in thread
From: Robert Jarzmik @ 2016-07-31 22:04 UTC (permalink / raw)
  To: Joe Perches
  Cc: Daniel Mack, Haojian Zhuang, Russell King, linux-arm-kernel,
	linux-kernel

Hi Joe,

Joe Perches <joe@perches.com> writes:
> 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);

Yeah, I thought about this when I made the patch.

I supposed it was written this way so that a printk was easier to add, that's
why I didn't change the useless variable.

I have no strong opinion about this, so if you think it's worth it I can make
the additional change.

Cheers.

--
Robert

^ permalink raw reply	[flat|nested] 4+ messages in thread
* Re: [PATCH v3] ARM: pxa: fix GPIO double shifts
  2016-07-31 22:04   ` Robert Jarzmik
@ 2016-07-31 22:22     ` Joe Perches
  0 siblings, 0 replies; 4+ messages in thread
From: Joe Perches @ 2016-07-31 22:22 UTC (permalink / raw)
  To: Robert Jarzmik
  Cc: Daniel Mack, Haojian Zhuang, Russell King, linux-arm-kernel,
	linux-kernel

On Mon, 2016-08-01 at 00:04 +0200, Robert Jarzmik wrote:
> Joe Perches <joe@perches.com> writes:
[]
> > 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);
> Yeah, I thought about this when I made the patch.
> 
> I supposed it was written this way so that a printk was easier to add, that's
> why I didn't change the useless variable.
> 
> I have no strong opinion about this, so if you think it's worth it I can make
> the additional change.

Hi Robert.  Your choice.

It was one of those, 'oh, bother' type of things but 
I think it's worth it for readability and consistency.

cheers, Joe

^ permalink raw reply	[flat|nested] 4+ messages in thread
end of thread, other threads:[~2016-07-31 22:22 UTC | newest]

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2016-07-31 12:17 [PATCH v3] ARM: pxa: fix GPIO double shifts Robert Jarzmik
2016-07-31 20:44 ` Joe Perches
2016-07-31 22:04   ` Robert Jarzmik
2016-07-31 22:22     ` Joe Perches

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