1 files changed, 98 insertions, 0 deletions

diff --git a/include/asm-generic/gpio.h b/include/asm-generic/gpio.h
index 2d0aab1d8611..f29a502f4a6c 100644
--- a/include/asm-generic/gpio.h
+++ b/include/asm-generic/gpio.h
@@ -1,6 +1,102 @@
 #ifndef _ASM_GENERIC_GPIO_H
 #define _ASM_GENERIC_GPIO_H
 
+#ifdef CONFIG_HAVE_GPIO_LIB
+
+/* 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.
+ */
+
+#ifndef ARCH_NR_GPIOS
+#define ARCH_NR_GPIOS           256
+#endif
+
+struct seq_file;
+
+/**
+ * struct gpio_chip - abstract a GPIO controller
+ * @label: for diagnostics
+ * @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"
+ * @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
+ *
+ * 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 {
+        char                    *label;
+
+        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);
+        void                    (*set)(struct gpio_chip *chip,
+                                                unsigned offset, int value);
+        void                    (*dbg_show)(struct seq_file *s,
+                                                struct gpio_chip *chip);
+        int                     base;
+        u16                     ngpio;
+        unsigned                can_sleep:1;
+};
+
+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);
+
+
+/* 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_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);
+
+
+#else
+
 /* platforms that don't directly support access to GPIOs through I2C, SPI,
  * or other blocking infrastructure can use these wrappers.
  */
@@ -22,4 +118,6 @@ static inline void gpio_set_value_cansleep(unsigned gpio, int value)
         gpio_set_value(gpio, value);
 }
 
+#endif
+
 #endif /* _ASM_GENERIC_GPIO_H */