Re: [PATCH v1 04/11] usb: phy: tegra: switch to using devm_gpiod_get()

[Guenter Roeck]

On 9/5/22 12:55, Andy Shevchenko wrote:
> On Mon, Sep 5, 2022 at 10:51 PM Dmitry Torokhov
> <dmitry.torokhov@xxxxxxxxx> wrote:
> > 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@xxxxxxxxx> 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@xxxxxxxxx> 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 has to do with a dead code. If defm_gpiod_get() does not return
> NULL, then why do we even bother to check?

PTR_ERR_OR_ZERO() converts into an error code (if the pointer is an
ERR_PTR) or 0 if it is a real pointer. Its purpose is not to convert
NULL into 0, its purpose is to convert a pointer either into an error
code or 0. That is what is done here, and it is done all over the place
in the kernel. I don't see your problem with it. Care to explain ?

> > 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).
>
> I don't see how this is relevant.

You lost me. Really, please explain your problem with PTR_ERR_OR_ZERO().

Thanks,
Guenter