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

[Andy Shevchenko]

On Mon, Sep 05, 2022 at 03:07:48PM -0700, Guenter Roeck wrote:
> 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(&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().

I don't know what I was thinking about... You, guys, are right, sorry for
my noise.

-- 
With Best Regards,
Andy Shevchenko