#ifndef __LINUX_GPIO_DRIVER_H
  #define __LINUX_GPIO_DRIVER_H
  
  #include <linux/types.h>
  #include <linux/module.h>
  
  struct device;
  struct gpio_desc;
  struct of_phandle_args;
  struct device_node;
  struct seq_file;
  
  /**
   * 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
   * @list: links gpio_chips together for traversal
   * @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
   * @get_direction: returns direction for signal "offset", 0=out, 1=in,
   *	(same as GPIOF_DIR_XXX), or negative error
   * @direction_input: configures signal "offset" as input, or returns error
   * @direction_output: configures signal "offset" as output, or returns error
   * @get: returns value for signal "offset"; for output signals this
   *	returns either the value actually sensed, or zero
   * @set: assigns output value for signal "offset"
   * @set_debounce: optional hook for setting debounce time for specified gpio in
   *      interrupt triggered gpio chips
   * @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).
   * @desc: array of ngpio descriptors. Private.
   * @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.
   * @can_sleep: flag must be set iff get()/set() methods sleep, as they
   *	must while accessing GPIO expander chips over I2C or SPI
   * @exported: flags if the gpiochip is exported for use from sysfs. Private.
   *
   * 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;
  	struct list_head        list;
  
  	int			(*request)(struct gpio_chip *chip,
  						unsigned offset);
  	void			(*free)(struct gpio_chip *chip,
  						unsigned offset);
  	int			(*get_direction)(struct gpio_chip *chip,
  						unsigned offset);
  	int			(*direction_input)(struct gpio_chip *chip,
  						unsigned offset);
  	int			(*direction_output)(struct gpio_chip *chip,
  						unsigned offset, int value);
  	int			(*get)(struct gpio_chip *chip,
  						unsigned offset);
  	void			(*set)(struct gpio_chip *chip,
  						unsigned offset, int value);
  	int			(*set_debounce)(struct gpio_chip *chip,
  						unsigned offset,
  						unsigned debounce);
  
  	int			(*to_irq)(struct gpio_chip *chip,
  						unsigned offset);
  
  	void			(*dbg_show)(struct seq_file *s,
  						struct gpio_chip *chip);
  	int			base;
  	u16			ngpio;
  	struct gpio_desc	*desc;
  	const char		*const *names;
  	bool			can_sleep;
  	bool			exported;
  
  #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
  #ifdef CONFIG_PINCTRL
  	/*
  	 * If CONFIG_PINCTRL is enabled, then gpio controllers can optionally
  	 * describe the actual pin range which they serve in an SoC. This
  	 * information would be used by pinctrl subsystem to configure
  	 * corresponding pins for gpio usage.
  	 */
  	struct list_head pin_ranges;
  #endif
  };
  
  extern const char *gpiochip_is_requested(struct gpio_chip *chip,
  			unsigned offset);
  
  /* 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(void *data,
  			      int (*match)(struct gpio_chip *chip, void *data));
  
  /* lock/unlock as IRQ */
  int gpiod_lock_as_irq(struct gpio_desc *desc);
  void gpiod_unlock_as_irq(struct gpio_desc *desc);
  
  enum gpio_lookup_flags {
  	GPIO_ACTIVE_HIGH = (0 << 0),
  	GPIO_ACTIVE_LOW = (1 << 0),
  	GPIO_OPEN_DRAIN = (1 << 1),
  	GPIO_OPEN_SOURCE = (1 << 2),
  };
  
  /**
   * struct gpiod_lookup - lookup table
   * @chip_label: name of the chip the GPIO belongs to
   * @chip_hwnum: hardware number (i.e. relative to the chip) of the GPIO
   * @con_id: name of the GPIO from the device's point of view
   * @idx: index of the GPIO in case several GPIOs share the same name
   * @flags: mask of GPIO_* values
   *
   * gpiod_lookup is a lookup table for associating GPIOs to specific devices and
   * functions using platform data.
   */
  struct gpiod_lookup {
  	const char *chip_label;
  	u16 chip_hwnum;
  	const char *con_id;
  	unsigned int idx;
  	enum gpio_lookup_flags flags;
  };
  
  struct gpiod_lookup_table {
  	struct list_head list;
  	const char *dev_id;
  	struct gpiod_lookup table[];
  };
  
  /*
   * Simple definition of a single GPIO under a con_id
   */
  #define GPIO_LOOKUP(_chip_label, _chip_hwnum, _con_id, _flags) \
  	GPIO_LOOKUP_IDX(_chip_label, _chip_hwnum, _con_id, 0, _flags)
  
  /*
   * Use this macro if you need to have several GPIOs under the same con_id.
   * Each GPIO needs to use a different index and can be accessed using
   * gpiod_get_index()
   */
  #define GPIO_LOOKUP_IDX(_chip_label, _chip_hwnum, _con_id, _idx, _flags)  \
  {                                                                         \
  	.chip_label = _chip_label,                                        \
  	.chip_hwnum = _chip_hwnum,                                        \
  	.con_id = _con_id,                                                \
  	.idx = _idx,                                                      \
  	.flags = _flags,                                                  \
  }
  
  void gpiod_add_lookup_table(struct gpiod_lookup_table *table);
  
  #endif