diff options
| -rw-r--r-- | Documentation/gpio.txt | 16 | ||||
| -rw-r--r-- | include/linux/gpio.h | 95 |
2 files changed, 107 insertions, 4 deletions
diff --git a/Documentation/gpio.txt b/Documentation/gpio.txt index 8da724e2a0f..54630095aa3 100644 --- a/Documentation/gpio.txt +++ b/Documentation/gpio.txt @@ -2,6 +2,9 @@ GPIO Interfaces This provides an overview of GPIO access conventions on Linux. +These calls use the gpio_* naming prefix. No other calls should use that +prefix, or the related __gpio_* prefix. + What is a GPIO? =============== @@ -69,11 +72,13 @@ in this document, but drivers acting as clients to the GPIO interface must not care how it's implemented.) That said, if the convention is supported on their platform, drivers should -use it when possible. Platforms should declare GENERIC_GPIO support in -Kconfig (boolean true), which multi-platform drivers can depend on when -using the include file: +use it when possible. Platforms must declare GENERIC_GPIO support in their +Kconfig (boolean true), and provide an <asm/gpio.h> file. Drivers that can't +work without standard GPIO calls should have Kconfig entries which depend +on GENERIC_GPIO. The GPIO calls are available, either as "real code" or as +optimized-away stubs, when drivers use the include file: - #include <asm/gpio.h> + #include <linux/gpio.h> If you stick to this convention then it'll be easier for other developers to see what your code is doing, and help maintain it. @@ -316,6 +321,9 @@ pulldowns integrated on some platforms. Not all platforms support them, or support them in the same way; and any given board might use external pullups (or pulldowns) so that the on-chip ones should not be used. (When a circuit needs 5 kOhm, on-chip 100 kOhm resistors won't do.) +Likewise drive strength (2 mA vs 20 mA) and voltage (1.8V vs 3.3V) is a +platform-specific issue, as are models like (not) having a one-to-one +correspondence between configurable pins and GPIOs. There are other system-specific mechanisms that are not specified here, like the aforementioned options for input de-glitching and wire-OR output. diff --git a/include/linux/gpio.h b/include/linux/gpio.h new file mode 100644 index 00000000000..4987a84078e --- /dev/null +++ b/include/linux/gpio.h @@ -0,0 +1,95 @@ +#ifndef __LINUX_GPIO_H +#define __LINUX_GPIO_H + +/* see Documentation/gpio.txt */ + +#ifdef CONFIG_GENERIC_GPIO +#include <asm/gpio.h> + +#else + +/* + * Some platforms don't support the GPIO programming interface. + * + * In case some driver uses it anyway (it should normally have + * depended on GENERIC_GPIO), these routines help the compiler + * optimize out much GPIO-related code ... or trigger a runtime + * warning when something is wrongly called. + */ + +static inline int gpio_is_valid(int number) +{ + return 0; +} + +static inline int gpio_request(unsigned gpio, const char *label) +{ + return -ENOSYS; +} + +static inline void gpio_free(unsigned gpio) +{ + /* GPIO can never have been requested */ + WARN_ON(1); +} + +static inline int gpio_direction_input(unsigned gpio) +{ + return -ENOSYS; +} + +static inline int gpio_direction_output(unsigned gpio, int value) +{ + return -ENOSYS; +} + +static inline int gpio_get_value(unsigned gpio) +{ + /* GPIO can never have been requested or set as {in,out}put */ + WARN_ON(1); + return 0; +} + +static inline void gpio_set_value(unsigned gpio, int value) +{ + /* GPIO can never have been requested or set as output */ + WARN_ON(1); +} + +static inline int gpio_cansleep(unsigned gpio) +{ + /* GPIO can never have been requested or set as {in,out}put */ + WARN_ON(1); + return 0; +} + +static inline int gpio_get_value_cansleep(unsigned gpio) +{ + /* GPIO can never have been requested or set as {in,out}put */ + WARN_ON(1); + return 0; +} + +static inline void gpio_set_value_cansleep(unsigned gpio, int value) +{ + /* GPIO can never have been requested or set as output */ + WARN_ON(1); +} + +static inline int gpio_to_irq(unsigned gpio) +{ + /* GPIO can never have been requested or set as input */ + WARN_ON(1); + return -EINVAL; +} + +static inline int irq_to_gpio(unsigned irq) +{ + /* irq can never have been returned from gpio_to_irq() */ + WARN_ON(1); + return -EINVAL; +} + +#endif + +#endif /* __LINUX_GPIO_H */ |