ACPI: thinkpad-acpi: check version of hot key firmware

Check the HKEY firmware version (HKEY.MHKV handler), and refuse to load if
it is unknown.  Use this instead of the presence of HKEY.DHKV to detect hot
key mask capability.
Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Signed-off-by: Len Brown <len.brown@intel.com>

drivers/misc/thinkpad_acpi.c

@@ -999,6 +999,7 @@ static int __init hotkey_init(struct ibm_init_struct *iibm)
 
 	int res, i;
 	int status;
+	int hkeyv;
 
 	vdbg_printk(TPACPI_DBG_INIT, "initializing hotkey subdriver\n");
 
@@ -1024,18 +1025,35 @@ static int __init hotkey_init(struct ibm_init_struct *iibm)
 			return res;
 
 		/* mask not supported on 570, 600e/x, 770e, 770x, A21e, A2xm/p,
-		   A30, R30, R31, T20-22, X20-21, X22-24 */
-		tp_features.hotkey_mask =
-			acpi_evalf(hkey_handle, NULL, "DHKN", "qv");
+		   A30, R30, R31, T20-22, X20-21, X22-24.  Detected by checking
+		   for HKEY interface version 0x100 */
+		if (acpi_evalf(hkey_handle, &hkeyv, "MHKV", "qd")) {
+			if ((hkeyv >> 8) != 1) {
+				printk(IBM_ERR "unknown version of the "
+				       "HKEY interface: 0x%x\n", hkeyv);
+				printk(IBM_ERR "please report this to %s\n",
+				       IBM_MAIL);
+			} else {
+				/*
+				 * MHKV 0x100 in A31, R40, R40e,
+				 * T4x, X31, and later
+				 * */
+				tp_features.hotkey_mask = 1;
+			}
+		}
 
 		vdbg_printk(TPACPI_DBG_INIT, "hotkey masks are %s\n",
 			str_supported(tp_features.hotkey_mask));
 
 		if (tp_features.hotkey_mask) {
-			/* MHKA available in A31, R40, R40e, T4x, X31, and later */
 			if (!acpi_evalf(hkey_handle, &hotkey_all_mask,
-					"MHKA", "qd"))
+					"MHKA", "qd")) {
+				printk(IBM_ERR
+				       "missing MHKA handler, "
+				       "please report this to %s\n",
+				       IBM_MAIL);
 				hotkey_all_mask = 0x080cU; /* FN+F12, FN+F4, FN+F3 */
+			}
 		}
 
 		res = hotkey_get(&hotkey_orig_status, &hotkey_orig_mask);