Input: joydev - allow binding to button-only devices

Dance pads don't have an axis, so allow this kind of controllers
to be used via legacy joystick interface.

Signed-off-by: Christoph Fritz <[e-mail]>
Signed-off-by: Dmitry Torokhov <[e-mail]>

drivers/input/joydev.c

···
 		.evbit = { BIT_MASK(EV_ABS) },
 		.absbit = { BIT_MASK(ABS_THROTTLE) },
 	},
+	{
+		.flags = INPUT_DEVICE_ID_MATCH_EVBIT |
+				INPUT_DEVICE_ID_MATCH_KEYBIT,
+		.evbit = { BIT_MASK(EV_KEY) },
+		.keybit = {[BIT_WORD(BTN_JOYSTICK)] = BIT_MASK(BTN_JOYSTICK) },
+	},
+	{
+		.flags = INPUT_DEVICE_ID_MATCH_EVBIT |
+				INPUT_DEVICE_ID_MATCH_KEYBIT,
+		.evbit = { BIT_MASK(EV_KEY) },
+		.keybit = { [BIT_WORD(BTN_GAMEPAD)] = BIT_MASK(BTN_GAMEPAD) },
+	},
+	{
+		.flags = INPUT_DEVICE_ID_MATCH_EVBIT |
+				INPUT_DEVICE_ID_MATCH_KEYBIT,
+		.evbit = { BIT_MASK(EV_KEY) },
+		.keybit = { [BIT_WORD(BTN_TRIGGER_HAPPY)] = BIT_MASK(BTN_TRIGGER_HAPPY) },
+	},
 	{ }	/* Terminating entry */
 };