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From: Linus Walleij <linus.walleij@linaro.org>
Date: Wed, 9 Nov 2016 09:44:41 +0100
Message-ID: <CACRpkdZ2LKpCT0mWN_-Chi-R3wY6DgiX4EWoKvwxfHFEGE2cfg@mail.gmail.com>
Subject: Re: [PATCH] ACPI / gpio: avoid warning for gpio hogging code
To: Arnd Bergmann <arnd@arndb.de>
Cc: Alexandre Courbot <gnurou@gmail.com>,
        Mika Westerberg <mika.westerberg@linux.intel.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
        Dmitry Torokhov <dmitry.torokhov@gmail.com>,
        Wei Yongjun <weiyongjun1@huawei.com>,
        Christophe Ricard <christophe.ricard@gmail.com>,
        "linux-gpio@vger.kernel.org" <linux-gpio@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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On Tue, Nov 8, 2016 at 2:40 PM, Arnd Bergmann <arnd@arndb.de> wrote:

> The newly added acpi_gpiochip_scan_gpios function produces a few harmless
> warnings:
>
> drivers/gpio/gpiolib-acpi.c: In function ‘acpi_gpiochip_add’:
> drivers/gpio/gpiolib-acpi.c:925:7: error: ‘dflags’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
> drivers/gpio/gpiolib-acpi.c:925:9: error: ‘lflags’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
>
> The problem is that he compiler cannot know that a negative return value
> from fwnode_property_read_u32_array() or acpi_gpiochip_pin_to_gpio_offset()
> implies that the IS_ERR(gpio_desc) is true, as the value could in theory
> be below -MAX_ERRNO.
>
> The function already initializes its output values to zero, and moving
> that intialization a little higher up ensures that we can never have
> uninitialized data in the caller.
>
> Fixes: c80f1ba75df2 ("ACPI / gpio: Add hogging support")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Patch applied with Mika's ACK.

Yours,
Linus Walleij