greybus: hid: add HID class driver

This adds HID transport layer driver for Greybus. Most of the stuff is
implemented, but is untested.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

drivers/staging/greybus/Makefile

@@ -14,6 +14,7 @@ gb-phy-y :=	gpb.o		\
 		uart.o	\
 		pwm.o	\
 		gpio.o	\
+		hid.o	\
 		i2c.o	\
 		spi.o	\
 		usb.o

drivers/staging/greybus/gpb.c

@@ -49,8 +49,14 @@ static int __init gpbridge_init(void)
 		pr_err("error initializing spi protocol\n");
 		goto error_spi;
 	}
+	if (gb_hid_protocol_init()) {
+		pr_err("error initializing hid protocol\n");
+		goto error_hid;
+	}
 	return 0;
 
+error_hid:
+	gb_spi_protocol_exit();
 error_spi:
 	gb_i2c_protocol_exit();
 error_i2c:
@@ -69,6 +75,7 @@ static int __init gpbridge_init(void)
 
 static void __exit gpbridge_exit(void)
 {
+	gb_hid_protocol_exit();
 	gb_spi_protocol_exit();
 	gb_i2c_protocol_exit();
 	gb_usb_protocol_exit();

drivers/staging/greybus/protocol.h

@@ -84,6 +84,9 @@ extern void gb_i2c_protocol_exit(void);
 extern int gb_spi_protocol_init(void);
 extern void gb_spi_protocol_exit(void);
 
+extern int gb_hid_protocol_init(void);
+extern void gb_hid_protocol_exit(void);
+
 #define gb_protocol_driver(__protocol)			\
 static int __init protocol_init(void)			\
 {							\