[PATCHv2] rtc: pcf8563: fix uninitialized use warning

[PATCHv2] rtc: pcf8563: fix uninitialized use warning

[Arnd Bergmann]

gcc-4.9 found a potential condition under which the 'pending'
variable may be used uninitialized:

drivers/rtc/rtc-pcf8563.c: In function 'pcf8563_irq':
drivers/rtc/rtc-pcf8563.c:173:5: warning: 'pending' may be used uninitialized in this function [-Wmaybe-uninitialized]

This is because in the pcf8563_get_alarm_mode() function, we
check any nonzero return of pcf8563_read_block_data, but
in the irq function we only check for negative values, so
a possible positive value does not get detected if the compiler
chooses not to inline the entire call chain.

Checking for any non-zero value in the interrupt handler as well
is just as correct and lets the compiler know what we are doing,
without needing a bogus initialization.

As pointed out by Sergei Shtylyov, the same code section contains
another bug: an interrupt handler is not supposed to return
an errno value. Let's fix this as well by returning IRQ_NONE
in case of a communication error.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>

diff --git a/drivers/rtc/rtc-pcf8563.c b/drivers/rtc/rtc-pcf8563.c
index 5a197d9dc7e7..c2ef0a22ee94 100644
--- a/drivers/rtc/rtc-pcf8563.c
+++ b/drivers/rtc/rtc-pcf8563.c
@@ -167,8 +167,8 @@ static irqreturn_t pcf8563_irq(int irq, void *dev_id)
 	char pending;
 
 	err = pcf8563_get_alarm_mode(pcf8563->client, NULL, &pending);
-	if (err < 0)
-		return err;
+	if (err)
+		return IRQ_NONE;
 
 	if (pending) {
 		rtc_update_irq(pcf8563->rtc, 1, RTC_IRQF | RTC_AF);

[PATCHv2] rtc: pcf8563: fix uninitialized use warning

[Sergei Shtylyov]

On 9/8/2014 7:26 PM, Arnd Bergmann wrote:

> gcc-4.9 found a potential condition under which the 'pending'
> variable may be used uninitialized:

> drivers/rtc/rtc-pcf8563.c: In function 'pcf8563_irq':
> drivers/rtc/rtc-pcf8563.c:173:5: warning: 'pending' may be used uninitialized in this function [-Wmaybe-uninitialized]

> This is because in the pcf8563_get_alarm_mode() function, we
> check any nonzero return of pcf8563_read_block_data, but
> in the irq function we only check for negative values, so
> a possible positive value does not get detected if the compiler
> chooses not to inline the entire call chain.

> Checking for any non-zero value in the interrupt handler as well
> is just as correct and lets the compiler know what we are doing,
> without needing a bogus initialization.

> As pointed out by Sergei Shtylyov, the same code section contains
> another bug: an interrupt handler is not supposed to return
> an errno value. Let's fix this as well by returning IRQ_NONE
> in case of a communication error.

> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

    If you're fixing both issues in one patch, it probably needs somewhat 
modified subject, like "rtc: pcf8356: fix error handling".

WBR, Sergei

[PATCH v3 1/2] rtc: pcf8563: fix uninitialized use warning

[Arnd Bergmann]

gcc-4.9 found a potential condition under which the 'pending'
variable may be used uninitialized:

drivers/rtc/rtc-pcf8563.c: In function 'pcf8563_irq':
drivers/rtc/rtc-pcf8563.c:173:5: warning: 'pending' may be used uninitialized in this function [-Wmaybe-uninitialized]

This is because in the pcf8563_get_alarm_mode() function, we
check any nonzero return of pcf8563_read_block_data, but
in the irq function we only check for negative values, so
a possible positive value does not get detected if the compiler
chooses not to inline the entire call chain.

Checking for any non-zero value in the interrupt handler as well
is just as correct and lets the compiler know what we are doing,
without needing a bogus initialization.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>

diff --git a/drivers/rtc/rtc-pcf8563.c b/drivers/rtc/rtc-pcf8563.c
index 5a197d9dc7e7..3a6f994c4da8 100644
--- a/drivers/rtc/rtc-pcf8563.c
+++ b/drivers/rtc/rtc-pcf8563.c
@@ -167,7 +167,7 @@ static irqreturn_t pcf8563_irq(int irq, void *dev_id)
 	char pending;
 
 	err = pcf8563_get_alarm_mode(pcf8563->client, NULL, &pending);
-	if (err < 0)
+	if (err)
 		return err;
 
 	if (pending) {

[PATCH v3 2/2] rtc: pcf8563: fix pcf8563_irq error return value

[Arnd Bergmann]

As pointed out by Sergei Shtylyov, the pcf8563_irq function
contains a bug in the error handling: an interrupt handler
is not supposed to return an errno value but an 'enum
irqreturn'.

Let's fix this by returning IRQ_NONE in case of a communication error.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>

diff --git a/drivers/rtc/rtc-pcf8563.c b/drivers/rtc/rtc-pcf8563.c
index 3a6f994c4da8..c2ef0a22ee94 100644
--- a/drivers/rtc/rtc-pcf8563.c
+++ b/drivers/rtc/rtc-pcf8563.c
@@ -168,7 +168,7 @@ static irqreturn_t pcf8563_irq(int irq, void *dev_id)
 
 	err = pcf8563_get_alarm_mode(pcf8563->client, NULL, &pending);
 	if (err)
-		return err;
+		return IRQ_NONE;
 
 	if (pending) {
 		rtc_update_irq(pcf8563->rtc, 1, RTC_IRQF | RTC_AF);