linux-kernel - Re: [PATCH v1 04/11] usb: phy: tegra: switch to using devm_gpiod

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Date:   Mon, 5 Sep 2022 12:51:39 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Matti Vaittinen <mazziesaccount@...il.com>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Claudiu Beznea <claudiu.beznea@...rochip.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Felipe Balbi <balbi@...nel.org>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Vignesh Raghavendra <vigneshr@...com>,
        Daniel Vetter <daniel@...ll.ch>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Marc Zyngier <maz@...nel.org>,
        Richard Weinberger <richard@....at>,
        David Airlie <airlied@...ux.ie>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Rob Herring <robh@...nel.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Pali Rohár <pali@...nel.org>,
        LINUXWATCHDOG <linux-watchdog@...r.kernel.org>,
        USB <linux-usb@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        linux-pci <linux-pci@...r.kernel.org>,
        linux-tegra <linux-tegra@...r.kernel.org>,
        "open list:MEMORY TECHNOLOGY..." <linux-mtd@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v1 04/11] usb: phy: tegra: switch to using
 devm_gpiod_get()

On Mon, Sep 05, 2022 at 10:41:40PM +0300, Andy Shevchenko wrote:
> On Mon, Sep 5, 2022 at 10:40 PM Dmitry Torokhov
> <dmitry.torokhov@...il.com> wrote:
> > On Mon, Sep 05, 2022 at 01:59:44PM +0300, Andy Shevchenko wrote:
> > > On Mon, Sep 5, 2022 at 9:32 AM Dmitry Torokhov
> > > <dmitry.torokhov@...il.com> wrote:
> 
> ...
> 
> > > > -               gpiod = devm_gpiod_get_from_of_node(&pdev->dev, np,
> > > > -                                                   "nvidia,phy-reset-gpio",
> > > > -                                                   0, GPIOD_OUT_HIGH,
> > > > -                                                   "ulpi_phy_reset_b");
> > > > +               gpiod = devm_gpiod_get(&pdev->dev, "nvidia,phy-reset",
> > > > +                                      GPIOD_OUT_HIGH);
> > > >                 err = PTR_ERR_OR_ZERO(gpiod);
> > >
> > > What does _OR_ZERO mean now?
> >
> > This converts a pointer to an error code if a pointer represents
> > ERR_PTR() encoded error, or 0 to indicate success.
> 
> Yes, I know that. My point is, how is it useful now (or even before)?
> I mean that devm_gpio_get() never returns NULL, right?

What does returning NULL have to do with anything. It converts a pointer
to a "classic" return code, with negative errors and 0 on success.

It allows to not use multiple IS_ERR/PTR_ERR in the code (I'd need 1
IS_ERR and 2 PTR_ERR, one in dev_err() and another to return).

Thanks.

-- 
Dmitry