linux-kernel - Re: [PATCHv2] rtc: pcf8563: fix uninitialized use warning

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Message-ID: <540DCEB0.6030108@cogentembedded.com>
Date:	Mon, 08 Sep 2014 19:43:44 +0400
From:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:	Arnd Bergmann <arnd@...db.de>,
	Alessandro Zummo <a.zummo@...ertech.it>
CC:	rtc-linux@...glegroups.com, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCHv2] rtc: pcf8563: fix uninitialized use warning

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@...db.de>

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

WBR, Sergei

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