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. Suggested-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx> --- This is a resend of a similar patch from a couple years ago. V2: - added paragraph to Documentation/gpio/consumer.txt at request of Alexandre Courbot - added Suggested-by: Uwe Kleine-König at request of Alexandre Courbot - hopefully addressed Uwe's concern about gpiolib being disabled in the patch description: I find it extremely unlikely that the optional GPIO would happen to be the only GPIO in the whole system. - added handling for more _optional() calls appeared since V1 was posted. Documentation/gpio/consumer.txt | 6 ++++++ include/linux/gpio/consumer.h | 12 ++++++------ 2 files changed, 12 insertions(+), 6 deletions(-) diff --git a/Documentation/gpio/consumer.txt b/Documentation/gpio/consumer.txt index 05676fdacfe3..912568baabb9 100644 --- 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 fb0fde686cb1..a0431f4aa6cc 100644 --- a/include/linux/gpio/consumer.h +++ b/include/linux/gpio/consumer.h @@ -165,14 +165,14 @@ 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 @@ -186,7 +186,7 @@ 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) @@ -226,14 +226,14 @@ 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 @@ -247,7 +247,7 @@ 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) -- 2.11.0.483.g087da7b7c-goog -- Dmitry -- To unsubscribe from this list: send the line "unsubscribe linux-gpio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html