| Message ID | 20150220003035.GA22334@dtor-glaptop |
|---|---|
| State | New |
| Headers | show |
On Fri, Feb 20, 2015 at 9:30 AM, Dmitry Torokhov <dmitry.torokhov@gmail.com> wrote: > 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. Interestingly Uwe sent a RFC for this one week ago: http://patchwork.ozlabs.org/patch/439135/ Maybe credit him with a Suggested-by.? I should have commented at that time, but let's do it now: I agree with the idea, but this leaves the door open to confusing situations in case gpiolib was unintentionally disabled. Could you also add a note in the documentation of this function to explain this behavior, to spare a few headaches to users of this function? > > Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com> > --- > include/linux/gpio/consumer.h | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/include/linux/gpio/consumer.h b/include/linux/gpio/consumer.h > index fd85cb1..f68244f 100644 > --- a/include/linux/gpio/consumer.h > +++ b/include/linux/gpio/consumer.h > @@ -132,14 +132,14 @@ 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 void gpiod_put(struct gpio_desc *desc) > @@ -171,14 +171,14 @@ 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 void devm_gpiod_put(struct device *dev, struct gpio_desc *desc) > -- > 2.2.0.rc0.207.ga3a616c > > > -- > Dmitry -- To unsubscribe from this list: send the line "unsubscribe linux-gpio" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Fri, Feb 20, 2015 at 01:59:43PM +0900, Alexandre Courbot wrote: > On Fri, Feb 20, 2015 at 9:30 AM, Dmitry Torokhov > <dmitry.torokhov@gmail.com> wrote: > > 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. > > Interestingly Uwe sent a RFC for this one week ago: > > http://patchwork.ozlabs.org/patch/439135/ > > Maybe credit him with a Suggested-by.? I certainly am fine with crediting him with Suggested-by even though I did not see that Uwe's e-mail but this patch was prompted by his other patch changing a few input drivers to use gpiod_get_optional() and me recalling that I explicitly did not use it as it made no difference from gpiod_get() since I had to handle -ENOSYS anyway. > > I should have commented at that time, but let's do it now: I agree > with the idea, but this leaves the door open to confusing situations > in case gpiolib was unintentionally disabled. Could you also add a > note in the documentation of this function to explain this behavior, > to spare a few headaches to users of this function? You mean the inline documentation in drivers/gpio/gpiolib.c and drivers/gpio/devres.c? I can certainly mention there that is GPIOLIB is disabled thy will return NULL unlike the non-optional variants. > > > > > Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com> > > --- > > include/linux/gpio/consumer.h | 8 ++++---- > > 1 file changed, 4 insertions(+), 4 deletions(-) > > > > diff --git a/include/linux/gpio/consumer.h b/include/linux/gpio/consumer.h > > index fd85cb1..f68244f 100644 > > --- a/include/linux/gpio/consumer.h > > +++ b/include/linux/gpio/consumer.h > > @@ -132,14 +132,14 @@ 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 void gpiod_put(struct gpio_desc *desc) > > @@ -171,14 +171,14 @@ 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 void devm_gpiod_put(struct device *dev, struct gpio_desc *desc) > > -- > > 2.2.0.rc0.207.ga3a616c > > > > > > -- > > Dmitry
On Fri, Feb 20, 2015 at 2:33 PM, Dmitry Torokhov <dmitry.torokhov@gmail.com> wrote: >> I should have commented at that time, but let's do it now: I agree >> with the idea, but this leaves the door open to confusing situations >> in case gpiolib was unintentionally disabled. Could you also add a >> note in the documentation of this function to explain this behavior, >> to spare a few headaches to users of this function? > > You mean the inline documentation in drivers/gpio/gpiolib.c and > drivers/gpio/devres.c? I can certainly mention there that is GPIOLIB is disabled > thy will return NULL unlike the non-optional variants. I was thinking about Documentation/gpio/consumer.txt, but having a note in the inline documentation as well certainly makes sense. -- To unsubscribe from this list: send the line "unsubscribe linux-gpio" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hello, On Thu, Feb 19, 2015 at 09:33:44PM -0800, Dmitry Torokhov wrote: > On Fri, Feb 20, 2015 at 01:59:43PM +0900, Alexandre Courbot wrote: > > On Fri, Feb 20, 2015 at 9:30 AM, Dmitry Torokhov > > <dmitry.torokhov@gmail.com> wrote: > > > 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. > > > > Interestingly Uwe sent a RFC for this one week ago: > > > > http://patchwork.ozlabs.org/patch/439135/ > > > > Maybe credit him with a Suggested-by.? > > I certainly am fine with crediting him with Suggested-by even though I did not > see that Uwe's e-mail but this patch was prompted by his other patch changing a > few input drivers to use gpiod_get_optional() and me recalling that I > explicitly did not use it as it made no difference from gpiod_get() since I had > to handle -ENOSYS anyway. Note that I'm not convinced any more this is a good idea. Consider you have a device tree entry specifying reset-gpio = <&gpio5 4 0>; for your device. With gpiod_get_optional(dev, "reset", GPIO_OUT_LOW); the drivers tells that some of the devices it can handle have a reset gpio. If the device in question does have such a gpio the driver must know and do something with it. If the device doesn't have such a gpio that's fine, too. But if GPIOLIB is off and the device has a reset-gpio specified you certainly want to error out, right? So IMHO the right thing to do is to return NULL iff there is no reset-gpio specified. Otherwise -ENOSYS is the right thing to return. Best regards Uwe
diff --git a/include/linux/gpio/consumer.h b/include/linux/gpio/consumer.h index fd85cb1..f68244f 100644 --- a/include/linux/gpio/consumer.h +++ b/include/linux/gpio/consumer.h @@ -132,14 +132,14 @@ 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 void gpiod_put(struct gpio_desc *desc) @@ -171,14 +171,14 @@ 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 void devm_gpiod_put(struct device *dev, struct gpio_desc *desc)
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. Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com> --- include/linux/gpio/consumer.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)