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

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);


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