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

From: Laxman Dewangan
Date: Thu Mar 10 2016 - 02:15:32 EST

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))

- 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;