From d8f388d8dc8d4f36539dd37c1fff62cc404ea0fc Mon Sep 17 00:00:00 2001 From: David Brownell Date: Fri, 25 Jul 2008 01:46:07 -0700 Subject: gpio: sysfs interface This adds a simple sysfs interface for GPIOs. /sys/class/gpio /export ... asks the kernel to export a GPIO to userspace /unexport ... to return a GPIO to the kernel /gpioN ... for each exported GPIO #N /value ... always readable, writes fail for input GPIOs /direction ... r/w as: in, out (default low); write high, low /gpiochipN ... for each gpiochip; #N is its first GPIO /base ... (r/o) same as N /label ... (r/o) descriptive, not necessarily unique /ngpio ... (r/o) number of GPIOs; numbered N .. N+(ngpio - 1) GPIOs claimed by kernel code may be exported by its owner using a new gpio_export() call, which should be most useful for driver debugging. Such exports may optionally be done without a "direction" attribute. Userspace may ask to take over a GPIO by writing to a sysfs control file, helping to cope with incomplete board support or other "one-off" requirements that don't merit full kernel support: echo 23 > /sys/class/gpio/export ... will gpio_request(23, "sysfs") and gpio_export(23); use /sys/class/gpio/gpio-23/direction to (re)configure it, when that GPIO can be used as both input and output. echo 23 > /sys/class/gpio/unexport ... will gpio_free(23), when it was exported as above The extra D-space footprint is a few hundred bytes, except for the sysfs resources associated with each exported GPIO. The additional I-space footprint is about two thirds of the current size of gpiolib (!). Since no /dev node creation is involved, no "udev" support is needed. Related changes: * This adds a device pointer to "struct gpio_chip". When GPIO providers initialize that, sysfs gpio class devices become children of that device instead of being "virtual" devices. * The (few) gpio_chip providers which have such a device node have been updated. * Some gpio_chip drivers also needed to update their module "owner" field ... for which missing kerneldoc was added. * Some gpio_chips don't support input GPIOs. Those GPIOs are now flagged appropriately when the chip is registered. Based on previous patches, and discussion both on and off LKML. A Documentation/ABI/testing/sysfs-gpio update is ready to submit once this merges to mainline. [akpm@linux-foundation.org: a few maintenance build fixes] Signed-off-by: David Brownell Cc: Guennadi Liakhovetski Cc: Greg KH Cc: Kay Sievers Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/asm-generic/gpio.h | 33 +++++++++++++++++++++++++++++++-- include/linux/gpio.h | 13 +++++++++++++ 2 files changed, 44 insertions(+), 2 deletions(-) (limited to 'include') diff --git a/include/asm-generic/gpio.h b/include/asm-generic/gpio.h index 6be061d09da9..1beff5166e53 100644 --- a/include/asm-generic/gpio.h +++ b/include/asm-generic/gpio.h @@ -32,6 +32,8 @@ struct module; /** * struct gpio_chip - abstract a GPIO controller * @label: for diagnostics + * @dev: optional device providing the GPIOs + * @owner: helps prevent removal of modules exporting active GPIOs * @direction_input: configures signal "offset" as input, or returns error * @get: returns value for signal "offset"; for output signals this * returns either the value actually sensed, or zero @@ -59,6 +61,7 @@ struct module; */ struct gpio_chip { char *label; + struct device *dev; struct module *owner; int (*direction_input)(struct gpio_chip *chip, @@ -74,6 +77,7 @@ struct gpio_chip { int base; u16 ngpio; unsigned can_sleep:1; + unsigned exported:1; }; extern const char *gpiochip_is_requested(struct gpio_chip *chip, @@ -108,7 +112,18 @@ extern void __gpio_set_value(unsigned gpio, int value); extern int __gpio_cansleep(unsigned gpio); -#else +#ifdef CONFIG_GPIO_SYSFS + +/* + * A sysfs interface can be exported by individual drivers if they want, + * but more typically is configured entirely from userspace. + */ +extern int gpio_export(unsigned gpio, bool direction_may_change); +extern void gpio_unexport(unsigned gpio); + +#endif /* CONFIG_GPIO_SYSFS */ + +#else /* !CONFIG_HAVE_GPIO_LIB */ static inline int gpio_is_valid(int number) { @@ -137,6 +152,20 @@ static inline void gpio_set_value_cansleep(unsigned gpio, int value) gpio_set_value(gpio, value); } -#endif +#endif /* !CONFIG_HAVE_GPIO_LIB */ + +#ifndef CONFIG_GPIO_SYSFS + +/* sysfs support is only available with gpiolib, where it's optional */ + +static inline int gpio_export(unsigned gpio, bool direction_may_change) +{ + return -ENOSYS; +} + +static inline void gpio_unexport(unsigned gpio) +{ +} +#endif /* CONFIG_GPIO_SYSFS */ #endif /* _ASM_GENERIC_GPIO_H */ diff --git a/include/linux/gpio.h b/include/linux/gpio.h index 98be6c5762b9..730a20b83576 100644 --- a/include/linux/gpio.h +++ b/include/linux/gpio.h @@ -79,6 +79,19 @@ static inline void gpio_set_value_cansleep(unsigned gpio, int value) WARN_ON(1); } +static inline int gpio_export(unsigned gpio, bool direction_may_change) +{ + /* GPIO can never have been requested or set as {in,out}put */ + WARN_ON(1); + return -EINVAL; +} + +static inline void gpio_unexport(unsigned gpio) +{ + /* GPIO can never have been exported */ + WARN_ON(1); +} + static inline int gpio_to_irq(unsigned gpio) { /* GPIO can never have been requested or set as input */ -- cgit v1.2.3-58-ga151