linux-kernel - [PATCH 3.16 041/306] ARM: pxa: fix GPIO double shifts

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Message-ID: <lsq.1487198500.620753871@decadent.org.uk>
Date:   Wed, 15 Feb 2017 22:41:40 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Joe Perches" <joe@...ches.com>,
        "Robert Jarzmik" <robert.jarzmik@...e.fr>,
        "Dan Carpenter" <dan.carpenter@...cle.com>
Subject: [PATCH 3.16 041/306] ARM: pxa: fix GPIO double shifts

3.16.40-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Robert Jarzmik <robert.jarzmik@...e.fr>

commit ca26475bf02ed8562b9b46f91d3e8b52ec312541 upstream.

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@...cle.com>
Cc: Joe Perches <joe@...ches.com>
Signed-off-by: Robert Jarzmik <robert.jarzmik@...e.fr>
[bwh: Backported to 3.16: adjust filename]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/arm/mach-pxa/corgi_pm.c                | 13 ++++---------
 arch/arm/mach-pxa/include/mach/sharpsl_pm.h |  2 +-
 arch/arm/mach-pxa/sharpsl_pm.c              |  2 +-
 arch/arm/mach-pxa/spitz_pm.c                |  9 +++------
 4 files changed, 9 insertions(+), 17 deletions(-)

--- a/arch/arm/mach-pxa/corgi_pm.c
+++ b/arch/arm/mach-pxa/corgi_pm.c
@@ -131,16 +131,11 @@ static int corgi_should_wakeup(unsigned
 	return is_resume;
 }
 
-static unsigned long corgi_charger_wakeup(void)
+static bool corgi_charger_wakeup(void)
 {
-	unsigned long 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));
-	return ret;
+	return !gpio_get_value(CORGI_GPIO_AC_IN) ||
+		!gpio_get_value(CORGI_GPIO_KEY_INT) ||
+		!gpio_get_value(CORGI_GPIO_WAKEUP);
 }
 
 unsigned long corgipm_read_devdata(int type)
--- 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(vo
 		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)
--- a/arch/arm/mach-pxa/include/mach/sharpsl_pm.h
+++ b/arch/arm/mach-pxa/include/mach/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);
--- a/arch/arm/mach-pxa/spitz_pm.c
+++ b/arch/arm/mach-pxa/spitz_pm.c
@@ -165,13 +165,10 @@ static int spitz_should_wakeup(unsigned
 	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));
-	return ret;
+	return !gpio_get_value(SPITZ_GPIO_KEY_INT) ||
+		gpio_get_value(SPITZ_GPIO_SYNC);
 }
 
 unsigned long spitzpm_read_devdata(int type)