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From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Tue, 3 Dec 2019 09:17:58 +0100
Message-ID: <CAMuHMdW-n8ao7t7156WYxRg7v8+ojXsRgHGUOax=9nBo2F5xOw@mail.gmail.com>
Subject: Re: [PATCH v3 5/7] gpio: Add GPIO Aggregator/Repeater driver
To:     Harish Jenny K N <harish_kandiga@mentor.com>
Cc:     Geert Uytterhoeven <geert+renesas@glider.be>,
        Linus Walleij <linus.walleij@linaro.org>,
        Bartosz Golaszewski <bgolaszewski@baylibre.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Eugeniu Rosca <erosca@de.adit-jv.com>,
        Alexander Graf <graf@amazon.com>,
        Peter Maydell <peter.maydell@linaro.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Phil Reid <preid@electromag.com.au>,
        Marc Zyngier <marc.zyngier@arm.com>,
        Christoffer Dall <christoffer.dall@arm.com>,
        Magnus Damm <magnus.damm@gmail.com>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>,
        Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
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Hi Harish,

On Tue, Dec 3, 2019 at 6:42 AM Harish Jenny K N
<harish_kandiga@mentor.com> wrote:
> > +static int gpio_aggregator_probe(struct platform_device *pdev)
> > +{
> > +     struct device *dev = &pdev->dev;
> > +     struct gpio_desc **descs;
> > +     struct gpiochip_fwd *fwd;
> > +     int i, n;
> > +
> > +     n = gpiod_count(dev, NULL);
> > +     if (n < 0)
> > +             return n;
> > +
> > +     descs = devm_kmalloc_array(dev, n, sizeof(*descs), GFP_KERNEL);
> > +     if (!descs)
> > +             return -ENOMEM;
> > +
> > +     for (i = 0; i < n; i++) {
> > +             descs[i] = devm_gpiod_get_index(dev, NULL, i, GPIOD_ASIS);
>
> can you please add this check as well as we need to return EPROBE_DEFER.
>
> if (desc[i] == ERR_PTR(-ENOENT))
> <                 return -EPROBE_DEFER;

So gpiod_get_index() nevers return -EPROBE_DEFER, but returns -ENOENT
instead?
How can a driver distinguish between "GPIO not found" and "gpiochip driver
not yet initialized"?
Worse, so the *_optional() variants will return NULL in both cases, too, so
the caller will always fall back to optional GPIO not present?

Or am I missing something?

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-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