1. 根目录:
2. include
3. asm-generic
4. gpio.h

#ifndef _ASM_GENERIC_GPIO_H
#define _ASM_GENERIC_GPIO_H

#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/of.h>

#ifdef CONFIG_GPIOLIB

#include <linux/compiler.h>

/* Platforms may implement their GPIO interface with library code,
 * at a small performance cost for non-inlined operations and some
 * extra memory (for code and for per-GPIO table entries).
 *
 * While the GPIO programming interface defines valid GPIO numbers
 * to be in the range 0..MAX_INT, this library restricts them to the
 * smaller range 0..ARCH_NR_GPIOS-1.
 *
 * ARCH_NR_GPIOS is somewhat arbitrary; it usually reflects the sum of
 * builtin/SoC GPIOs plus a number of GPIOs on expanders; the latter is
 * actually an estimate of a board-specific value.
 */

#ifndef ARCH_NR_GPIOS
#define ARCH_NR_GPIOS		256
#endif

/*
 * "valid" GPIO numbers are nonnegative and may be passed to
 * setup routines like gpio_request().  only some valid numbers
 * can successfully be requested and used.
 *
 * Invalid GPIO numbers are useful for indicating no-such-GPIO in
 * platform data and other tables.
 */

static inline bool gpio_is_valid(int number)
{
	return number >= 0 && number < ARCH_NR_GPIOS;
}

struct device;
struct gpio;
struct seq_file;
struct module;
struct device_node;

/**
 * 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
 * @request: optional hook for chip-specific activation, such as
 *	enabling module power and clock; may sleep
 * @free: optional hook for chip-specific deactivation, such as
 *	disabling module power and clock; may sleep
 * @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
 * @direction_output: configures signal "offset" as output, or returns error
 * @set: assigns output value for signal "offset"
 * @to_irq: optional hook supporting non-static gpio_to_irq() mappings;
 *	implementation may not sleep
 * @dbg_show: optional routine to show contents in debugfs; default code
 *	will be used when this is omitted, but custom code can show extra
 *	state (such as pullup/pulldown configuration).
 * @base: identifies the first GPIO number handled by this chip; or, if
 *	negative during registration, requests dynamic ID allocation.
 * @ngpio: the number of GPIOs handled by this controller; the last GPIO
 *	handled is (base + ngpio - 1).
 * @can_sleep: flag must be set iff get()/set() methods sleep, as they
 *	must while accessing GPIO expander chips over I2C or SPI
 * @names: if set, must be an array of strings to use as alternative
 *      names for the GPIOs in this chip. Any entry in the array
 *      may be NULL if there is no alias for the GPIO, however the
 *      array must be @ngpio entries long.  A name can include a single printk
 *      format specifier for an unsigned int.  It is substituted by the actual
 *      number of the gpio.
 *
 * A gpio_chip can help platforms abstract various sources of GPIOs so
 * they can all be accessed through a common programing interface.
 * Example sources would be SOC controllers, FPGAs, multifunction
 * chips, dedicated GPIO expanders, and so on.
 *
 * Each chip controls a number of signals, identified in method calls
 * by "offset" values in the range 0..(@ngpio - 1).  When those signals
 * are referenced through calls like gpio_get_value(gpio), the offset
 * is calculated by subtracting @base from the gpio number.
 */
struct gpio_chip {
	const char		*label;
	struct device		*dev;
	struct module		*owner;

	int			(*request)(struct gpio_chip *chip,
						unsigned offset);
	void			(*free)(struct gpio_chip *chip,
						unsigned offset);

	int			(*direction_input)(struct gpio_chip *chip,
						unsigned offset);
	int			(*get)(struct gpio_chip *chip,
						unsigned offset);
	int			(*direction_output)(struct gpio_chip *chip,
						unsigned offset, int value);
	int			(*set_debounce)(struct gpio_chip *chip,
						unsigned offset, unsigned debounce);

	void			(*set)(struct gpio_chip *chip,
						unsigned offset, int value);

	int			(*to_irq)(struct gpio_chip *chip,
						unsigned offset);

	void			(*dbg_show)(struct seq_file *s,
						struct gpio_chip *chip);
	int			base;
	u16			ngpio;
	const char		*const *names;
	unsigned		can_sleep:1;
	unsigned		exported:1;

#if defined(CONFIG_OF_GPIO)
	/*
	 * If CONFIG_OF is enabled, then all GPIO controllers described in the
	 * device tree automatically may have an OF translation
	 */
	struct device_node *of_node;
	int of_gpio_n_cells;
	int (*of_xlate)(struct gpio_chip *gc,
		        const struct of_phandle_args *gpiospec, u32 *flags);
#endif
};

extern const char *gpiochip_is_requested(struct gpio_chip *chip,
			unsigned offset);
extern struct gpio_chip *gpio_to_chip(unsigned gpio);
extern int __must_check gpiochip_reserve(int start, int ngpio);

/* add/remove chips */
extern int gpiochip_add(struct gpio_chip *chip);
extern int __must_check gpiochip_remove(struct gpio_chip *chip);
extern struct gpio_chip *gpiochip_find(const void *data,
					int (*match)(struct gpio_chip *chip,
						     const void *data));


/* Always use the library code for GPIO management calls,
 * or when sleeping may be involved.
 */
extern int gpio_request(unsigned gpio, const char *label);
extern void gpio_free(unsigned gpio);

extern int gpio_direction_input(unsigned gpio);
extern int gpio_direction_output(unsigned gpio, int value);

extern int gpio_set_debounce(unsigned gpio, unsigned debounce);

extern int gpio_get_value_cansleep(unsigned gpio);
extern void gpio_set_value_cansleep(unsigned gpio, int value);


/* A platform's <asm/gpio.h> code may want to inline the I/O calls when
 * the GPIO is constant and refers to some always-present controller,
 * giving direct access to chip registers and tight bitbanging loops.
 */
extern int __gpio_get_value(unsigned gpio);
extern void __gpio_set_value(unsigned gpio, int value);

extern int __gpio_cansleep(unsigned gpio);

extern int __gpio_to_irq(unsigned gpio);

extern int gpio_request_one(unsigned gpio, unsigned long flags, const char *label);
extern int gpio_request_array(const struct gpio *array, size_t num);
extern void gpio_free_array(const struct gpio *array, size_t num);

/* bindings for managed devices that want to request gpios */
int devm_gpio_request(struct device *dev, unsigned gpio, const char *label);
void devm_gpio_free(struct device *dev, unsigned int gpio);

#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 int gpio_export_link(struct device *dev, const char *name,
			unsigned gpio);
extern int gpio_sysfs_set_active_low(unsigned gpio, int value);
extern void gpio_unexport(unsigned gpio);

#endif	/* CONFIG_GPIO_SYSFS */

#else	/* !CONFIG_GPIOLIB */

static inline bool gpio_is_valid(int number)
{
	/* only non-negative numbers are valid */
	return number >= 0;
}

/* platforms that don't directly support access to GPIOs through I2C, SPI,
 * or other blocking infrastructure can use these wrappers.
 */

static inline int gpio_cansleep(unsigned gpio)
{
	return 0;
}

static inline int gpio_get_value_cansleep(unsigned gpio)
{
	might_sleep();
	return __gpio_get_value(gpio);
}

static inline void gpio_set_value_cansleep(unsigned gpio, int value)
{
	might_sleep();
	__gpio_set_value(gpio, value);
}

#endif /* !CONFIG_GPIOLIB */

#ifndef CONFIG_GPIO_SYSFS

struct device;

/* 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 int gpio_export_link(struct device *dev, const char *name,
				unsigned gpio)
{
	return -ENOSYS;
}

static inline int gpio_sysfs_set_active_low(unsigned gpio, int value)
{
	return -ENOSYS;
}

static inline void gpio_unexport(unsigned gpio)
{
}
#endif	/* CONFIG_GPIO_SYSFS */

#endif /* _ASM_GENERIC_GPIO_H */