gpio: Add comments on #if/#else/#endif

Improve readability a bit by commenting #if/#else/#endif statements
with the checked preprocessor symbols.

Signed-off-by: Enrico Weigelt <[e-mail]>
Signed-off-by: Linus Walleij <[e-mail]>

include/linux/gpio/driver.h

···
 	 */
 	void		(*irq_disable)(struct irq_data *data);
 };
-#endif
+#endif /* CONFIG_GPIOLIB_IRQCHIP */
 
 /**
  * struct gpio_chip - abstract a GPIO controller
···
 	spinlock_t bgpio_lock;
 	unsigned long bgpio_data;
 	unsigned long bgpio_dir;
-#endif
+#endif /* CONFIG_GPIO_GENERIC */
 
 #ifdef CONFIG_GPIOLIB_IRQCHIP
 	/*
···
 	 * used to handle IRQs for most practical cases.
 	 */
 	struct gpio_irq_chip irq;
-#endif
+#endif /* CONFIG_GPIOLIB_IRQCHIP */
 
 	/**
 	 * @need_valid_mask:
···
 	 */
 	int (*of_xlate)(struct gpio_chip *gc,
 			const struct of_phandle_args *gpiospec, u32 *flags);
-#endif
+#endif /* CONFIG_OF_GPIO */
 };
 
 extern const char *gpiochip_is_requested(struct gpio_chip *chip,
···
 	})
 #else
 #define gpiochip_add_data(chip, data) gpiochip_add_data_with_key(chip, data, NULL, NULL)
-#endif
+#endif /* CONFIG_LOCKDEP */
 
 static inline int gpiochip_add(struct gpio_chip *chip)
 {
···
 #define BGPIOF_READ_OUTPUT_REG_SET	BIT(4) /* reg_set stores output value */
 #define BGPIOF_NO_OUTPUT		BIT(5) /* only input */
 
-#endif
+#endif /* CONFIG_GPIO_GENERIC */
 
 #ifdef CONFIG_GPIOLIB_IRQCHIP
 
···
 					handler, type, true,
 					&lock_key, &request_key);
 }
-#else
+#else /* ! CONFIG_LOCKDEP */
 static inline int gpiochip_irqchip_add(struct gpio_chip *gpiochip,
 				       struct irq_chip *irqchip,
 				       unsigned int first_irq,
···
 			unsigned int gpio_offset, const char *pin_group);
 void gpiochip_remove_pin_ranges(struct gpio_chip *chip);
 
-#else
+#else /* ! CONFIG_PINCTRL */
 
 static inline int
 gpiochip_add_pin_range(struct gpio_chip *chip, const char *pinctl_name,

include/linux/gpio/gpio-reg.h

···
 
 int gpio_reg_resume(struct gpio_chip *gc);
 
-#endif
+#endif /* GPIO_REG_H */

include/linux/gpio/machine.h

···
 void gpiod_add_lookup_tables(struct gpiod_lookup_table **tables, size_t n);
 void gpiod_remove_lookup_table(struct gpiod_lookup_table *table);
 void gpiod_add_hogs(struct gpiod_hog *hogs);
-#else
+#else /* ! CONFIG_GPIOLIB */
 static inline
 void gpiod_add_lookup_table(struct gpiod_lookup_table *table) {}
 static inline
···
 static inline
 void gpiod_remove_lookup_table(struct gpiod_lookup_table *table) {}
 static inline void gpiod_add_hogs(struct gpiod_hog *hogs) {}
-#endif
+#endif /* CONFIG_GPIOLIB */
 
 #endif /* __LINUX_GPIO_MACHINE_H */