[PATCH] gpiolib: of_find_gpio(): Don't discard errors

[PATCH] gpiolib: of_find_gpio(): Don't discard errors

[Lars-Peter Clausen]

Since commit dd34c37aa3e8 ("gpio: of: Allow -gpio suffix for property
names") when requesting a GPIO from the devicetree gpiolib looks for
properties with both the '-gpio' and the '-gpios' suffix. This was
implemented by first searching for the property with the '-gpios' suffix
and if that yields an error try the '-gpio' suffix. This approach has the
issue that any error returned when looking for the '-gpios' suffix is
silently discarded.

Commit 06fc3b70f1dc ("gpio: of: Fix handling for deferred probe for -gpio
suffix") partially addressed the issue by treating the EPROBE_DEFER error
as a special condition. This fixed the case when the property is specified,
but the GPIO provider is not ready yet. But there are other cases in which
of_get_named_gpiod_flags() returns an error even though the property is
specified, e.g. if the specification is incorrect.

of_find_gpio() should only try to look for the property with the '-gpio'
suffix if no property with the '-gpios' suffix was found. If the property
was not found of_get_named_gpiod_flags() will return -ENOENT, so update the
condition to abort and propagate the error to the caller in all other
cases.

This is important for gpiod_get_optinal() and friends to behave correctly
in case the specifier contains errors. Without this patch they'll return
NULL if the property uses the '-gpios' suffix and the specifier contains
errors, which falsely indicates to the caller that no GPIO was specified.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
---
 drivers/gpio/gpiolib.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 6566b93..8f1d51b 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -2838,7 +2838,7 @@ static struct gpio_desc *of_find_gpio(struct device *dev, const char *con_id,
 
 		desc = of_get_named_gpiod_flags(dev->of_node, prop_name, idx,
 						&of_flags);
-		if (!IS_ERR(desc) || (PTR_ERR(desc) == -EPROBE_DEFER))
+		if (!IS_ERR(desc) || (PTR_ERR(desc) != -ENOENT))
 			break;
 	}
 
-- 
2.1.4

Re: [PATCH] gpiolib: of_find_gpio(): Don't discard errors

[Linus Walleij]

On Fri, Jul 1, 2016 at 5:40 PM, Lars-Peter Clausen <lars@metafoo.de> wrote:

> Since commit dd34c37aa3e8 ("gpio: of: Allow -gpio suffix for property
> names") when requesting a GPIO from the devicetree gpiolib looks for
> properties with both the '-gpio' and the '-gpios' suffix. This was
> implemented by first searching for the property with the '-gpios' suffix
> and if that yields an error try the '-gpio' suffix. This approach has the
> issue that any error returned when looking for the '-gpios' suffix is
> silently discarded.
>
> Commit 06fc3b70f1dc ("gpio: of: Fix handling for deferred probe for -gpio
> suffix") partially addressed the issue by treating the EPROBE_DEFER error
> as a special condition. This fixed the case when the property is specified,
> but the GPIO provider is not ready yet. But there are other cases in which
> of_get_named_gpiod_flags() returns an error even though the property is
> specified, e.g. if the specification is incorrect.
>
> of_find_gpio() should only try to look for the property with the '-gpio'
> suffix if no property with the '-gpios' suffix was found. If the property
> was not found of_get_named_gpiod_flags() will return -ENOENT, so update the
> condition to abort and propagate the error to the caller in all other
> cases.
>
> This is important for gpiod_get_optinal() and friends to behave correctly
> in case the specifier contains errors. Without this patch they'll return
> NULL if the property uses the '-gpios' suffix and the specifier contains
> errors, which falsely indicates to the caller that no GPIO was specified.
>
> Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>

This makes all kind of sense. Patch applied.

Yours,
Linus Walleij