gpio: adp5588-gpio: support interrupt controller

Implement irq_chip functionality on ADP5588/5587 GPIO expanders.  Only
level sensitive interrupts are supported.  Interrupts provided by this
irq_chip must be requested using request_threaded_irq().
Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/gpio/Kconfig

@@ -272,6 +272,13 @@ config GPIO_ADP5588
 	  To compile this driver as a module, choose M here: the module will be
 	  called adp5588-gpio.
 
+config GPIO_ADP5588_IRQ
+	bool "Interrupt controller support for ADP5588"
+	depends on GPIO_ADP5588=y
+	help
+	  Say yes here to enable the adp5588 to be used as an interrupt
+	  controller. It requires the driver to be built in the kernel.
+
 comment "PCI GPIO expanders:"
 
 config GPIO_CS5535

include/linux/i2c/adp5588.h

@@ -74,6 +74,20 @@
 
 #define ADP5588_DEVICE_ID_MASK	0xF
 
+ /* Configuration Register1 */
+#define ADP5588_AUTO_INC	(1 << 7)
+#define ADP5588_GPIEM_CFG	(1 << 6)
+#define ADP5588_INT_CFG		(1 << 4)
+#define ADP5588_GPI_IEN		(1 << 1)
+
+/* Interrupt Status Register */
+#define ADP5588_GPI_INT		(1 << 1)
+#define ADP5588_KE_INT		(1 << 0)
+
+#define ADP5588_MAXGPIO		18
+#define ADP5588_BANK(offs)	((offs) >> 3)
+#define ADP5588_BIT(offs)	(1u << ((offs) & 0x7))
+
 /* Put one of these structures in i2c_board_info platform_data */
 
 #define ADP5588_KEYMAPSIZE	80
@@ -128,6 +142,7 @@ struct adp5588_kpad_platform_data {
 
 struct adp5588_gpio_platform_data {
 	unsigned gpio_start;		/* GPIO Chip base # */
+	unsigned irq_base;		/* interrupt base # */
 	unsigned pullup_dis_mask;	/* Pull-Up Disable Mask */
 	int	(*setup)(struct i2c_client *client,
 				int gpio, unsigned ngpio,