linux-kernel - Re: [PATCH v3 5/7] gpio: Add GPIO Aggregator/Repeater driver

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Date:   Wed, 27 Nov 2019 15:33:34 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Eugeniu Rosca <erosca@...adit-jv.com>
Cc:     Geert Uytterhoeven <geert+renesas@...der.be>,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Jonathan Corbet <corbet@....net>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Harish Jenny K N <harish_kandiga@...tor.com>,
        Alexander Graf <graf@...zon.com>,
        Peter Maydell <peter.maydell@...aro.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Phil Reid <preid@...ctromag.com.au>,
        Marc Zyngier <marc.zyngier@....com>,
        Christoffer Dall <christoffer.dall@....com>,
        Magnus Damm <magnus.damm@...il.com>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        QEMU Developers <qemu-devel@...gnu.org>,
        Eugeniu Rosca <roscaeugeniu@...il.com>
Subject: Re: [PATCH v3 5/7] gpio: Add GPIO Aggregator/Repeater driver

Hi Eugeniu,

On Wed, Nov 27, 2019 at 3:15 PM Eugeniu Rosca <erosca@...adit-jv.com> wrote:
> On Wed, Nov 27, 2019 at 09:42:51AM +0100, Geert Uytterhoeven wrote:
> > +static bool isrange(const char *s)
> > +{
> > +     size_t n = strlen(s);
>
> Cppcheck 1.40-18521-ge6d692d96058:
> drivers/gpio/gpio-aggregator.c:69:11: style: Variable 'n' is assigned a value that is never used. [unreadVariable]
>
> Smatch v0.5.0-6150-gc1ed13e4ee7b:
> drivers/gpio/gpio-aggregator.c:69 isrange() warn: unused return: n = strlen()

Correct, this is a remainder of code present temporarily during development.
Will drop.

(where are the days gcc itself warned about that?)

> > +     aggr->lookups->dev_id = kasprintf(GFP_KERNEL, "%s.%d", DRV_NAME, id);
> > +     if (!aggr->lookups) {
> > +             res = -ENOMEM;
> > +             goto remove_idr;
> > +     }
>
> s/aggr->lookups/aggr->lookups->dev_id/ ?

Thanks, will fix.

> > +static int gpio_fwd_get_multiple(struct gpio_chip *chip, unsigned long *mask,
> > +                              unsigned long *bits)
> > +{
> > +     struct gpiochip_fwd *fwd = gpiochip_get_data(chip);
> > +     unsigned long *values, flags;
>
> gcc 9.2.1:
> warning: ‘flags’ may be used uninitialized in this function [-Wmaybe-uninitialized]
>
> [..]
>
> > +static void gpio_fwd_set_multiple(struct gpio_chip *chip, unsigned long *mask,
> > +                               unsigned long *bits)
> > +{
> > +     struct gpiochip_fwd *fwd = gpiochip_get_data(chip);
> > +     unsigned long *values, flags;
>
> gcc 9.2.1, same as above:
> warning: ‘flags’ may be used uninitialized in this function [-Wmaybe-uninitialized]

So newer gcc is (again) no longer smart enough to notice the check is
the same for initializer and user...

> Should these be silenced like in 2bf593f101f3ca ("xilinx_uartps.c:
> suppress "may be used uninitialised" warning") ?

TBH, I'm not a big fan of silencing false positives.
But if people like to see flags preinitialized to zero, that can be done...

> I plan to do some runtime testing soon.

Thanks, looking forward to the results!

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds