gpio: return NULL from gpiod_get_optional when GPIOLIB is disabled

Given the intent behind gpiod_get_optional() and friends it does not make
sense to return -ENOSYS when GPIOLIB is disabled: the driver is expected to
work just fine without gpio so let's behave as if gpio was not found.
Otherwise we have to special-case -ENOSYS in drivers.

Note that there was objection that someone might forget to enable GPIOLIB
when dealing with a platform that has device that actually specifies
optional gpio and we'll break it. I find this unconvincing as that would
have to be the *only GPIO* in the system, which is extremely unlikely.

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

diff --git a/Documentation/gpio/consumer.txt b/Documentation/gpio/consumer.txt
index 05676fdacfe3c56f1a9afdaf54795e9167a9c287..912568baabb9629083151fc4ed30578c066684cd 100644 (file)
--- a/Documentation/gpio/consumer.txt
+++ b/Documentation/gpio/consumer.txt
@@ -70,6 +70,12 @@ instead of -ENOENT if no GPIO has been assigned to the requested function:
                                                   unsigned int index,
                                                   enum gpiod_flags flags)
 
+Note that gpio_get*_optional() functions (and their managed variants), unlike
+the rest of gpiolib API, also return NULL when gpiolib support is disabled.
+This is helpful to driver authors, since they do not need to special case
+-ENOSYS return codes.  System integrators should however be careful to enable
+gpiolib on systems that need it.
+
 For a function using multiple GPIOs all of those can be obtained with one call:
 
        struct gpio_descs *gpiod_get_array(struct device *dev,

diff --git a/include/linux/gpio/consumer.h b/include/linux/gpio/consumer.h
index 2484b2fcc6eb58d0139605359fe97b285df8e5f5..13daf08e25bb2e5f3238553e7522fd0994293aa8 100644 (file)
--- a/include/linux/gpio/consumer.h
+++ b/include/linux/gpio/consumer.h
@@ -179,14 +179,14 @@ static inline struct gpio_desc *__must_check
 gpiod_get_optional(struct device *dev, const char *con_id,
                   enum gpiod_flags flags)
 {
-       return ERR_PTR(-ENOSYS);
+       return NULL;
 }
 
 static inline struct gpio_desc *__must_check
 gpiod_get_index_optional(struct device *dev, const char *con_id,
                         unsigned int index, enum gpiod_flags flags)
 {
-       return ERR_PTR(-ENOSYS);
+       return NULL;
 }
 
 static inline struct gpio_descs *__must_check
@@ -200,7 +200,7 @@ static inline struct gpio_descs *__must_check
 gpiod_get_array_optional(struct device *dev, const char *con_id,
                         enum gpiod_flags flags)
 {
-       return ERR_PTR(-ENOSYS);
+       return NULL;
 }
 
 static inline void gpiod_put(struct gpio_desc *desc)
@@ -240,14 +240,14 @@ static inline struct gpio_desc *__must_check
 devm_gpiod_get_optional(struct device *dev, const char *con_id,
                          enum gpiod_flags flags)
 {
-       return ERR_PTR(-ENOSYS);
+       return NULL;
 }
 
 static inline struct gpio_desc *__must_check
 devm_gpiod_get_index_optional(struct device *dev, const char *con_id,
                                unsigned int index, enum gpiod_flags flags)
 {
-       return ERR_PTR(-ENOSYS);
+       return NULL;
 }
 
 static inline struct gpio_descs *__must_check
@@ -261,7 +261,7 @@ static inline struct gpio_descs *__must_check
 devm_gpiod_get_array_optional(struct device *dev, const char *con_id,
                              enum gpiod_flags flags)
 {
-       return ERR_PTR(-ENOSYS);
+       return NULL;
 }
 
 static inline void devm_gpiod_put(struct device *dev, struct gpio_desc *desc)