Add KEY_MICMUTE and enable it on Lenovo X220

I suspect that this works on T410.
Signed-off-by: Andy Lutomirski <luto@mit.edu>
Signed-off-by: Matthew Garrett <mjg@redhat.com>

drivers/platform/x86/thinkpad_acpi.c

@@ -3185,9 +3185,18 @@ static int __init hotkey_init(struct ibm_init_struct *iibm)
 
 		KEY_VENDOR,	/* 0x17: Thinkpad/AccessIBM/Lenovo */
 
+		/* (assignments unknown, please report if found) */
+		KEY_UNKNOWN, KEY_UNKNOWN,
+
+		/*
+		 * The mic mute button only sends 0x1a.  It does not
+		 * automatically mute the mic or change the mute light.
+		 */
+		KEY_MICMUTE,	/* 0x1a: Mic mute (since ?400 or so) */
+
 		/* (assignments unknown, please report if found) */
 		KEY_UNKNOWN, KEY_UNKNOWN, KEY_UNKNOWN, KEY_UNKNOWN,
-		KEY_UNKNOWN, KEY_UNKNOWN, KEY_UNKNOWN, KEY_UNKNOWN,
+		KEY_UNKNOWN,
 		},
 	};
 

include/linux/input.h

@@ -438,6 +438,8 @@ struct input_keymap_entry {
 #define KEY_WIMAX		246
 #define KEY_RFKILL		247	/* Key that controls all radios */
 
+#define KEY_MICMUTE		248	/* Mute / unmute the microphone */
+
 /* Code 255 is reserved for special needs of AT keyboard driver */
 
 #define BTN_MISC		0x100