gpio: Add viperboard gpio driver

This adds the mfd cell to use the gpio a and gpio b part
of the Nano River Technologies viperboard.
Signed-off-by: Lars Poeschel <poeschel@lemonage.de>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

drivers/gpio/Kconfig

@@ -649,4 +649,17 @@ config GPIO_MSIC
 	  Enable support for GPIO on intel MSIC controllers found in
 	  intel MID devices
 
+comment "USB GPIO expanders:"
+
+config GPIO_VIPERBOARD
+	tristate "Viperboard GPIO a & b support"
+	depends on MFD_VIPERBOARD && USB
+	help
+	  Say yes here to access the GPIO signals of Nano River
+	  Technologies Viperboard. There are two GPIO chips on the
+	  board: gpioa and gpiob.
+          See viperboard API specification and Nano
+          River Tech's viperboard.h for detailed meaning
+          of the module parameters.
+
 endif

drivers/gpio/Makefile

@@ -71,6 +71,7 @@ obj-$(CONFIG_GPIO_TPS65912)	+= gpio-tps65912.o
 obj-$(CONFIG_GPIO_TWL4030)	+= gpio-twl4030.o
 obj-$(CONFIG_GPIO_TWL6040)	+= gpio-twl6040.o
 obj-$(CONFIG_GPIO_UCB1400)	+= gpio-ucb1400.o
+obj-$(CONFIG_GPIO_VIPERBOARD)	+= gpio-viperboard.o
 obj-$(CONFIG_GPIO_VR41XX)	+= gpio-vr41xx.o
 obj-$(CONFIG_GPIO_VT8500)	+= gpio-vt8500.o
 obj-$(CONFIG_GPIO_VX855)	+= gpio-vx855.o

drivers/mfd/viperboard.c

@@ -38,6 +38,9 @@ static const struct usb_device_id vprbrd_table[] = {
 MODULE_DEVICE_TABLE(usb, vprbrd_table);
 
 static struct mfd_cell vprbrd_devs[] = {
+	{
+		.name = "viperboard-gpio",
+	},
 };
 
 static int vprbrd_probe(struct usb_interface *interface,

include/linux/mfd/viperboard.h

@@ -44,6 +44,8 @@
 #define VPRBRD_USB_TIMEOUT_MS       100
 #define VPRBRD_USB_REQUEST_MAJOR    0xea
 #define VPRBRD_USB_REQUEST_MINOR    0xeb
+#define VPRBRD_USB_REQUEST_GPIOA    0xed
+#define VPRBRD_USB_REQUEST_GPIOB    0xdd
 
 struct vprbrd_i2c_write_hdr {
 	u8 cmd;