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[PATCH 0/5] gpio: of: Add error handling and support for multiple gpio in gpio-hog

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  [PATCH 0/5] gpio: of: Add error handling and support for multiple gpio in gpio-hog Laxman Dewangan <ldewangan@nvidia.com> - 2016-03-08 13:20 +0100
    [PATCH 3/5] gpio: of: Return error if gpio hog configuration failed Laxman Dewangan <ldewangan@nvidia.com> - 2016-03-08 13:20 +0100
      Re: [PATCH 3/5] gpio: of: Return error if gpio hog configuration  failed Thierry Reding <treding@nvidia.com> - 2016-03-08 15:30 +0100
      Re: [PATCH 3/5] gpio: of: Return error if gpio hog configuration  failed Stephen Warren <swarren@wwwdotorg.org> - 2016-03-09 18:20 +0100
        Re: [PATCH 3/5] gpio: of: Return error if gpio hog configuration  failed Laxman Dewangan <ldewangan@nvidia.com> - 2016-03-10 08:20 +0100

#1352950 — [PATCH 0/5] gpio: of: Add error handling and support for multiple gpio in gpio-hog

This series enhance the error print by adding error number in print message,
handle the error if gpio_hogd() fails and returns error to caller, and
add the support of multiple GPIOs to be passed from property "gpios" under
gpio hogd node.

Laxman Dewangan (5):
  gpio: of: Scan available child node for gpio-hog
  gpio: gpiolib: Print error number if gpio hog failed
  gpio: of: Return error if gpio hog configuration failed
  gpio: of: Add support to have multiple gpios in gpio-hog
  gpio: DT: Rephrase property "gpios" of hog node to support multiple
    gpios

 Documentation/devicetree/bindings/gpio/gpio.txt |  6 +-
 drivers/gpio/gpiolib-of.c                       | 73 +++++++++++++++++++------
 drivers/gpio/gpiolib.c                          |  9 +--
 3 files changed, 63 insertions(+), 25 deletions(-)

-- 
2.1.4

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#1352951 — [PATCH 3/5] gpio: of: Return error if gpio hog configuration failed

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(-)

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)
-- 
2.1.4

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#1353097 — Re: [PATCH 3/5] gpio: of: Return error if gpio hog configuration failed

[Multipart message — attachments visible in raw view] — view raw

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>

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#1354297 — Re: [PATCH 3/5] gpio: of: Return error if gpio hog configuration failed

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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#1354895 — Re: [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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