[3/5] gpio: of: Return error if gpio hog configuration failed
diff mbox

Message ID 1457438528-29054-4-git-send-email-ldewangan@nvidia.com
State New
Headers show

Commit Message

Laxman Dewangan March 8, 2016, 12:02 p.m. UTC
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.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Cc: Benoit Parrot <bparrot@ti.com>
Cc: Alexandre Courbot <acourbot@nvidia.com>
---
 drivers/gpio/gpiolib-of.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

Comments

Thierry Reding March 8, 2016, 2:23 p.m. UTC | #1
On Tue, Mar 08, 2016 at 05:32:06PM +0530, 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.
> 
> Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
> Cc: Benoit Parrot <bparrot@ti.com>
> Cc: Alexandre Courbot <acourbot@nvidia.com>
> ---
>  drivers/gpio/gpiolib-of.c | 15 +++++++++------
>  1 file changed, 9 insertions(+), 6 deletions(-)

Reviewed-by: Thierry Reding <treding@nvidia.com>
Stephen Warren March 9, 2016, 5:11 p.m. UTC | #2
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?
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Laxman Dewangan March 10, 2016, 7:02 a.m. UTC | #3
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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Patch
diff mbox

diff --git a/drivers/gpio/gpiolib-of.c b/drivers/gpio/gpiolib-of.c
index f2ba1a4..d81dbd8 100644
--- a/drivers/gpio/gpiolib-of.c
+++ b/drivers/gpio/gpiolib-of.c
@@ -201,14 +201,16 @@  static struct gpio_desc *of_parse_own_gpio(struct device_node *np,
  *
  * This is only used by of_gpiochip_add to request/set GPIO initial
  * configuration.
+ * It retures error if it fails otherwise 0 on success.
  */
-static void of_gpiochip_scan_gpios(struct gpio_chip *chip)
+static int of_gpiochip_scan_gpios(struct gpio_chip *chip)
 {
 	struct gpio_desc *desc = NULL;
 	struct device_node *np;
 	const char *name;
 	enum gpio_lookup_flags lflags;
 	enum gpiod_flags dflags;
+	int ret;
 
 	for_each_available_child_of_node(chip->of_node, np) {
 		if (!of_property_read_bool(np, "gpio-hog"))
@@ -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;
 }
 
 /**
@@ -442,9 +447,7 @@  int of_gpiochip_add(struct gpio_chip *chip)
 
 	of_node_get(chip->of_node);
 
-	of_gpiochip_scan_gpios(chip);
-
-	return 0;
+	return of_gpiochip_scan_gpios(chip);
 }
 
 void of_gpiochip_remove(struct gpio_chip *chip)