linux-kernel - Re: [PATCH] gpio: gpio-dwapb: add optional reset

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Message-ID: <CACRpkdbS6b9GW8HXmthOfaRPFMARMpyNGaR8He5BJbtfOXLMVw@mail.gmail.com>
Date:   Wed, 11 Oct 2017 10:31:06 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Alan Tull <atull@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>
Cc:     Hoan Tran <hotran@....com>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] gpio: gpio-dwapb: add optional reset

On Tue, Oct 10, 2017 at 11:26 PM, Alan Tull <atull@...nel.org> wrote:

> Some platforms require reset to be released to allow register
> access.
>
> Signed-off-by: Alan Tull <atull@...nel.org>

Fair enough.

(...)
> +       rst = devm_reset_control_get_optional_exclusive(dev, NULL);
> +       if (IS_ERR(rst)) {
> +               if (PTR_ERR(rst) == -EPROBE_DEFER)
> +                       return PTR_ERR(rst);
> +       } else {
> +               reset_control_deassert(rst);
> +               gpio->rst = rst;
> +       }

I do not see why any error other than -EPROBE_DEFER
should be ignored?

I guess the _optional API returns NULL if there is no
reset line so it should be fine to just return the error on
any error.

> +       if (gpio->rst)
> +               reset_control_assert(gpio->rst);

Is this the right way to handle an optional reset line?

Yours,
Linus Walleij