[PATCH] gpio: consumer: Remove WARN_ON(1) when GPIOLIB is disabled

[PATCH] gpio: consumer: Remove WARN_ON(1) when GPIOLIB is disabled

[Fabio Estevam]

gpiod_get_optional() returns NULL when GPIOLIB is disabled since
commit 22c403676dbbb7c6 ("gpio: return NULL from gpiod_get_optional when
GPIOLIB is disabled").

However, many gpiod functions still have WARN_ON(1) in their
GPIOLIB=n stubs, which causes warnings in drivers even if the
GPIO descriptor is requested via gpiod_get_optional().

Prior to commit 22c403676dbbb7c6 ("gpio: return NULL from
gpiod_get_optional when GPIOLIB is disabled") it was indeed true
the comment: "GPIO can never have been requested" as gpiod_get_optional()
used to return an error.

After this commit the returned value is NULL, so the comment and
WARN_ON(1) are no longer accurate.

An example of this kernel warning can be see in this report:
https://www.spinics.net/lists/kernel/msg2563045.html

Remove the WARN_ON(1) so that drivers can silently work fine
without kernel warnings when GPIOLIB is disabled.

Reported-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
---
Changes since RFC:
- Expand a bit on the commit log
- Include the kernel warning example

 include/linux/gpio/consumer.h | 59 -------------------------------------------
 1 file changed, 59 deletions(-)

diff --git a/include/linux/gpio/consumer.h b/include/linux/gpio/consumer.h
index 8f702fc..40c1be5 100644
--- a/include/linux/gpio/consumer.h
+++ b/include/linux/gpio/consumer.h
@@ -197,17 +197,11 @@ gpiod_get_array_optional(struct device *dev, const char *con_id,
 static inline void gpiod_put(struct gpio_desc *desc)
 {
 	might_sleep();
-
-	/* GPIO can never have been requested */
-	WARN_ON(1);
 }
 
 static inline void gpiod_put_array(struct gpio_descs *descs)
 {
 	might_sleep();
-
-	/* GPIO can never have been requested */
-	WARN_ON(1);
 }
 
 static inline struct gpio_desc *__must_check
@@ -254,150 +248,99 @@ devm_gpiod_get_array_optional(struct device *dev, const char *con_id,
 {
 	return NULL;
 }
-
 static inline void devm_gpiod_put(struct device *dev, struct gpio_desc *desc)
 {
 	might_sleep();
-
-	/* GPIO can never have been requested */
-	WARN_ON(1);
 }
-
 static inline void devm_gpiod_put_array(struct device *dev,
 					struct gpio_descs *descs)
 {
 	might_sleep();
-
-	/* GPIO can never have been requested */
-	WARN_ON(1);
 }
-
-
 static inline int gpiod_get_direction(const struct gpio_desc *desc)
 {
-	/* GPIO can never have been requested */
-	WARN_ON(1);
 	return -ENOSYS;
 }
 static inline int gpiod_direction_input(struct gpio_desc *desc)
 {
-	/* GPIO can never have been requested */
-	WARN_ON(1);
 	return -ENOSYS;
 }
 static inline int gpiod_direction_output(struct gpio_desc *desc, int value)
 {
-	/* GPIO can never have been requested */
-	WARN_ON(1);
 	return -ENOSYS;
 }
 static inline int gpiod_direction_output_raw(struct gpio_desc *desc, int value)
 {
-	/* GPIO can never have been requested */
-	WARN_ON(1);
 	return -ENOSYS;
 }
 
-
 static inline int gpiod_get_value(const struct gpio_desc *desc)
 {
-	/* GPIO can never have been requested */
-	WARN_ON(1);
 	return 0;
 }
 static inline void gpiod_set_value(struct gpio_desc *desc, int value)
 {
-	/* GPIO can never have been requested */
-	WARN_ON(1);
 }
 static inline void gpiod_set_array_value(unsigned int array_size,
 					 struct gpio_desc **desc_array,
 					 int *value_array)
 {
-	/* GPIO can never have been requested */
-	WARN_ON(1);
 }
 static inline int gpiod_get_raw_value(const struct gpio_desc *desc)
 {
-	/* GPIO can never have been requested */
-	WARN_ON(1);
 	return 0;
 }
 static inline void gpiod_set_raw_value(struct gpio_desc *desc, int value)
 {
-	/* GPIO can never have been requested */
-	WARN_ON(1);
 }
 static inline void gpiod_set_raw_array_value(unsigned int array_size,
 					     struct gpio_desc **desc_array,
 					     int *value_array)
 {
-	/* GPIO can never have been requested */
-	WARN_ON(1);
 }
 
 static inline int gpiod_get_value_cansleep(const struct gpio_desc *desc)
 {
-	/* GPIO can never have been requested */
-	WARN_ON(1);
 	return 0;
 }
 static inline void gpiod_set_value_cansleep(struct gpio_desc *desc, int value)
 {
-	/* GPIO can never have been requested */
-	WARN_ON(1);
 }
 static inline void gpiod_set_array_value_cansleep(unsigned int array_size,
 					    struct gpio_desc **desc_array,
 					    int *value_array)
 {
-	/* GPIO can never have been requested */
-	WARN_ON(1);
 }
 static inline int gpiod_get_raw_value_cansleep(const struct gpio_desc *desc)
 {
-	/* GPIO can never have been requested */
-	WARN_ON(1);
 	return 0;
 }
 static inline void gpiod_set_raw_value_cansleep(struct gpio_desc *desc,
 						int value)
 {
-	/* GPIO can never have been requested */
-	WARN_ON(1);
 }
 static inline void gpiod_set_raw_array_value_cansleep(unsigned int array_size,
 						struct gpio_desc **desc_array,
 						int *value_array)
 {
-	/* GPIO can never have been requested */
-	WARN_ON(1);
 }
 
 static inline int gpiod_set_debounce(struct gpio_desc *desc, unsigned debounce)
 {
-	/* GPIO can never have been requested */
-	WARN_ON(1);
 	return -ENOSYS;
 }
 
 static inline int gpiod_is_active_low(const struct gpio_desc *desc)
 {
-	/* GPIO can never have been requested */
-	WARN_ON(1);
 	return 0;
 }
 static inline int gpiod_cansleep(const struct gpio_desc *desc)
 {
-	/* GPIO can never have been requested */
-	WARN_ON(1);
 	return 0;
 }
 
 static inline int gpiod_to_irq(const struct gpio_desc *desc)
 {
-	/* GPIO can never have been requested */
-	WARN_ON(1);
 	return -EINVAL;
 }
 
@@ -408,8 +351,6 @@ static inline struct gpio_desc *gpio_to_desc(unsigned gpio)
 
 static inline int desc_to_gpio(const struct gpio_desc *desc)
 {
-	/* GPIO can never have been requested */
-	WARN_ON(1);
 	return -EINVAL;
 }
 
-- 
2.7.4

Re: [PATCH] gpio: consumer: Remove WARN_ON(1) when GPIOLIB is disabled

[Thierry Reding]

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On Fri, Jul 28, 2017 at 01:21:26PM -0300, Fabio Estevam wrote:
> gpiod_get_optional() returns NULL when GPIOLIB is disabled since
> commit 22c403676dbbb7c6 ("gpio: return NULL from gpiod_get_optional when
> GPIOLIB is disabled").
> 
> However, many gpiod functions still have WARN_ON(1) in their
> GPIOLIB=n stubs, which causes warnings in drivers even if the
> GPIO descriptor is requested via gpiod_get_optional().
> 
> Prior to commit 22c403676dbbb7c6 ("gpio: return NULL from
> gpiod_get_optional when GPIOLIB is disabled") it was indeed true
> the comment: "GPIO can never have been requested" as gpiod_get_optional()
> used to return an error.
> 
> After this commit the returned value is NULL, so the comment and
> WARN_ON(1) are no longer accurate.
> 
> An example of this kernel warning can be see in this report:
> https://www.spinics.net/lists/kernel/msg2563045.html
> 
> Remove the WARN_ON(1) so that drivers can silently work fine
> without kernel warnings when GPIOLIB is disabled.
> 
> Reported-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
> Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
> ---
> Changes since RFC:
> - Expand a bit on the commit log
> - Include the kernel warning example
> 
>  include/linux/gpio/consumer.h | 59 -------------------------------------------
>  1 file changed, 59 deletions(-)

How about cases where the GPIO was not optional? Do we still want those
to be silently ignored? I guess in some way that makes sense as well,
but after this patch we're deviating from existing behaviour for non-
optional GPIOs.

Also, if we do decide that we want to silently ignore all GPIO calls if
GPIOLIB is disabled, maybe it would still be a good idea to warn users
about this at least once, so that they don't go chasing wild geese?

In either case, I think the commit message is still confusing because
you're arguing that gpiod_get_optional() now returns NULL and therefore
it is fine to remove WARN_ON(), whereas the WARN_ON() would still be
valid for non-NULL GPIO descriptors (such as requested via gpiod_get()
when GPIOLIB=n.

Thierry

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Re: [PATCH] gpio: consumer: Remove WARN_ON(1) when GPIOLIB is disabled

[Linus Walleij]

On Fri, Jul 28, 2017 at 6:21 PM, Fabio Estevam <fabio.estevam@nxp.com> wrote:

> gpiod_get_optional() returns NULL when GPIOLIB is disabled since
> commit 22c403676dbbb7c6 ("gpio: return NULL from gpiod_get_optional when
> GPIOLIB is disabled").
>
> However, many gpiod functions still have WARN_ON(1) in their
> GPIOLIB=n stubs, which causes warnings in drivers even if the
> GPIO descriptor is requested via gpiod_get_optional().
>
> Prior to commit 22c403676dbbb7c6 ("gpio: return NULL from
> gpiod_get_optional when GPIOLIB is disabled") it was indeed true
> the comment: "GPIO can never have been requested" as gpiod_get_optional()
> used to return an error.
>
> After this commit the returned value is NULL, so the comment and
> WARN_ON(1) are no longer accurate.
>
> An example of this kernel warning can be see in this report:
> https://www.spinics.net/lists/kernel/msg2563045.html
>
> Remove the WARN_ON(1) so that drivers can silently work fine
> without kernel warnings when GPIOLIB is disabled.
>
> Reported-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
> Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>

I explained in another commend why I see this as a non-issue.

Drivers that call GPIO accessors likely need them to work properly.

If they see these messages I suspect it is because of missing
depends on or select of GPIOLIB in their Kconfig.

Yours,
Linus Walleij