| Message ID | 20171210002340.18460-1-linus.walleij@linaro.org |
|---|---|
| State | New |
| Headers | show |
| Series | gpio: Add helpers to determin direction of gpiods | expand |
Hey Linus, thanks for doing this. On Sun, Dec 10, 2017 at 01:23:40AM +0100, Linus Walleij wrote: > The gpiod_get_direction() returns 1 for input and 0 for output > but it's pretty hard to remember which one is which and generally > unintuitive and messy to provide #defines so let's simply add > two static inlines to do the job. > > Cc: Wolfram Sang <wsa@the-dreams.de> > Suggested-by: Wolfram Sang <wsa@the-dreams.de> > Signed-off-by: Linus Walleij <linus.walleij@linaro.org> > --- > Documentation/gpio/consumer.txt | 14 +++++++++++--- > include/linux/gpio/consumer.h | 25 +++++++++++++++++++++++++ > 2 files changed, 36 insertions(+), 3 deletions(-) You need to fix the kerneldoc for 'gpiod_get_direction", too. It still mentions GPIOF_DIR_*. > +static inline bool gpiod_is_input(struct gpio_desc *desc) > +{ > + int ret = gpiod_get_direction(desc); > + if (ret < 0) { > + pr_err("GPIO: failed to get direction\n"); Is that really helpful for the user if we don't say which GPIO failed? > + /* It is usually safest to assume we are input */ > + return true; > + } > + return !!ret; > +} Regards, Wolfram
Hi Linus, On Sun, Dec 10, 2017 at 1:23 AM, Linus Walleij <linus.walleij@linaro.org> wrote: > The gpiod_get_direction() returns 1 for input and 0 for output > but it's pretty hard to remember which one is which and generally > unintuitive and messy to provide #defines so let's simply add > two static inlines to do the job. > > Cc: Wolfram Sang <wsa@the-dreams.de> > Suggested-by: Wolfram Sang <wsa@the-dreams.de> > Signed-off-by: Linus Walleij <linus.walleij@linaro.org> > --- > Documentation/gpio/consumer.txt | 14 +++++++++++--- > include/linux/gpio/consumer.h | 25 +++++++++++++++++++++++++ > 2 files changed, 36 insertions(+), 3 deletions(-) > > diff --git a/Documentation/gpio/consumer.txt b/Documentation/gpio/consumer.txt > index 63e1bd1d88e3..c4b8e3d8c29f 100644 > --- a/Documentation/gpio/consumer.txt > +++ b/Documentation/gpio/consumer.txt > @@ -184,7 +184,15 @@ A driver can also query the current direction of a GPIO: > > int gpiod_get_direction(const struct gpio_desc *desc) > > -This function will return either GPIOF_DIR_IN or GPIOF_DIR_OUT. > +This function will return either 1 (input) or 0 (output). There are also > +these convenience helpers: > + > + bool gpiod_is_input(const struct gpio_desc *desc) > + bool gpiod_is_output(const struct gpio_desc *desc) > + > +These will not provide the same level of error fallbacks: if they fail to > +obtain the direction, they will print an error and report as input since this > +is usually safest. Leaving a pin configured as input is indeed the safest, from a hardware point of view. But I don't know if reporting to software that it is input is safe ;-) Can this actually fail? > --- a/include/linux/gpio/consumer.h > +++ b/include/linux/gpio/consumer.h > @@ -487,6 +487,31 @@ struct gpio_desc *devm_fwnode_get_index_gpiod_from_child(struct device *dev, > > #endif /* CONFIG_GPIOLIB */ > > +/* > + * Helpers that quickly tell whether a line is input or output. > + */ > +static inline bool gpiod_is_input(struct gpio_desc *desc) > +{ > + int ret = gpiod_get_direction(desc); > + if (ret < 0) { > + pr_err("GPIO: failed to get direction\n"); Do we really want a copy of this string in every module using this function? If you want to keep the error message, the function should be moved to the GPIO code, I think. > + /* It is usually safest to assume we are input */ > + return true; > + } > + return !!ret; > +} > + > +static inline bool gpiod_is_output(struct gpio_desc *desc) > +{ > + int ret = gpiod_get_direction(desc); > + if (ret < 0) { > + pr_err("GPIO: failed to get direction\n"); Likewise. > + /* It is usually safest to assume we are input */ > + return false; > + } > + return !ret; > +} Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds -- 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 Tue, Dec 12, 2017 at 11:42 PM, Wolfram Sang <wsa@the-dreams.de> wrote: >> Documentation/gpio/consumer.txt | 14 +++++++++++--- > > You need to fix the kerneldoc for 'gpiod_get_direction", too. It still > mentions GPIOF_DIR_*. More places? I can't find them! I thought the patch removed that here: -This function will return either GPIOF_DIR_IN or GPIOF_DIR_OUT. +This function will return either 1 (input) or 0 (output). There are also +these convenience helpers: I can only find it in Documentation/gpio/gpio-legacy.txt which is fine. >> +static inline bool gpiod_is_input(struct gpio_desc *desc) >> +{ >> + int ret = gpiod_get_direction(desc); >> + if (ret < 0) { >> + pr_err("GPIO: failed to get direction\n"); > > Is that really helpful for the user if we don't say which GPIO failed? I would have to add yet more APIs to do that. Hm. Together with Geert's comments I start to lean towards actually just creating two new #defines in <linux/consumer.h>. It has the upside that we can also check the return value for errors. Yours, Linus Walleij -- 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
> > You need to fix the kerneldoc for 'gpiod_get_direction", too. It still > > mentions GPIOF_DIR_*. > > More places? I can't find them! drivers/gpio/gpiolib.c Line 198 in both 4.15-rc3 and linux-next. Or as I said, the kerneldoc of gpiod_get_direction ;) > Together with Geert's comments I start to lean towards actually > just creating two new #defines in <linux/consumer.h>. > > It has the upside that we can also check the return value > for errors. Sounds good, in deed.
diff --git a/Documentation/gpio/consumer.txt b/Documentation/gpio/consumer.txt index 63e1bd1d88e3..c4b8e3d8c29f 100644 --- a/Documentation/gpio/consumer.txt +++ b/Documentation/gpio/consumer.txt @@ -162,8 +162,8 @@ The device-managed variants are, unsurprisingly: Using GPIOs =========== -Setting Direction ------------------ +Setting and Getting Direction +----------------------------- The first thing a driver must do with a GPIO is setting its direction. If no direction-setting flags have been given to gpiod_get*(), this is done by invoking one of the gpiod_direction_*() functions: @@ -184,7 +184,15 @@ A driver can also query the current direction of a GPIO: int gpiod_get_direction(const struct gpio_desc *desc) -This function will return either GPIOF_DIR_IN or GPIOF_DIR_OUT. +This function will return either 1 (input) or 0 (output). There are also +these convenience helpers: + + bool gpiod_is_input(const struct gpio_desc *desc) + bool gpiod_is_output(const struct gpio_desc *desc) + +These will not provide the same level of error fallbacks: if they fail to +obtain the direction, they will print an error and report as input since this +is usually safest. Be aware that there is no default direction for GPIOs. Therefore, **using a GPIO without setting its direction first is illegal and will result in undefined diff --git a/include/linux/gpio/consumer.h b/include/linux/gpio/consumer.h index 7447d85dbe2f..4e5ee3ec1913 100644 --- a/include/linux/gpio/consumer.h +++ b/include/linux/gpio/consumer.h @@ -487,6 +487,31 @@ struct gpio_desc *devm_fwnode_get_index_gpiod_from_child(struct device *dev, #endif /* CONFIG_GPIOLIB */ +/* + * Helpers that quickly tell whether a line is input or output. + */ +static inline bool gpiod_is_input(struct gpio_desc *desc) +{ + int ret = gpiod_get_direction(desc); + if (ret < 0) { + pr_err("GPIO: failed to get direction\n"); + /* It is usually safest to assume we are input */ + return true; + } + return !!ret; +} + +static inline bool gpiod_is_output(struct gpio_desc *desc) +{ + int ret = gpiod_get_direction(desc); + if (ret < 0) { + pr_err("GPIO: failed to get direction\n"); + /* It is usually safest to assume we are input */ + return false; + } + return !ret; +} + static inline struct gpio_desc *devm_fwnode_get_gpiod_from_child(struct device *dev, const char *con_id,
The gpiod_get_direction() returns 1 for input and 0 for output but it's pretty hard to remember which one is which and generally unintuitive and messy to provide #defines so let's simply add two static inlines to do the job. Cc: Wolfram Sang <wsa@the-dreams.de> Suggested-by: Wolfram Sang <wsa@the-dreams.de> Signed-off-by: Linus Walleij <linus.walleij@linaro.org> --- Documentation/gpio/consumer.txt | 14 +++++++++++--- include/linux/gpio/consumer.h | 25 +++++++++++++++++++++++++ 2 files changed, 36 insertions(+), 3 deletions(-) -- 2.14.3 -- 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