Re: [PATCH 3/5] gpio: of: Return error if gpio hog configuration failed

[Laxman Dewangan]

On Wednesday 09 March 2016 10:41 PM, Stephen Warren wrote:
> On 03/08/2016 05:02 AM, Laxman Dewangan wrote:
> > If GPIO hog configuration failed while adding OF based
> > gpiochip() then return the error instead of ignoring it.
> >
> > This helps of properly handling the gpio driver dependency.
> >
> > When adding the gpio hog nodes for NVIDIA's Tegra210 platforms,
> > the gpio_hogd() fails with EPROBE_DEFER because pinctrl is not
> > ready at this time and gpio_request() for Tegra GPIO driver
> > returns error. The error was not causing the Tegra GPIO driver
> > to fail as the error was getting ignored.
>
> > diff --git a/drivers/gpio/gpiolib-of.c b/drivers/gpio/gpiolib-of.c
>
> > @@ -218,9 +220,12 @@ static void of_gpiochip_scan_gpios(struct 
> > gpio_chip *chip)
> >           if (IS_ERR(desc))
> >               continue;
> >
> > -        if (gpiod_hog(desc, name, lflags, dflags))
> > -            continue;
> > +        ret = gpiod_hog(desc, name, lflags, dflags);
> > +        if (ret < 0)
> > +            return ret;
> >       }
> > +
> > +    return 0;
> >   }
>
> If there are multiple child nodes (which the code above is looping 
> over), and the hog for entries 0, 1, 2 succeed and the hog for entry 3 
> fails, don't you need to go back and unhog for nodes 0..2 so that the 
> next time this function is called, those hogs won't already be in 
> place thus preventing them from being hogged the second time around? 
> Or does hogging not take ownership of the resource and thus prevent it 
> from being acquired again?

The gpiolib take care per the error handling:

        status = of_gpiochip_add(chip);
        if (status)
                goto err_remove_chip;

:::
err_remove_chip:
        acpi_gpiochip_remove(chip);
        gpiochip_free_hogs(chip);
        of_gpiochip_remove(chip);