Input: ALPS - fix touchpad detection when buttons are pressed

ALPS touchpad detection fails if some buttons of ALPS are pressed.
The reason is that the "E6" query response byte is different from
what is expected.

This was tested on a Toshiba Portege R500.

Cc: stable <stable@vger.kernel.org>
Signed-off-by: Akio Idehara <zbe64533@gmail.com>
Tested-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

Documentation/input/alps.txt

@@ -13,7 +13,8 @@ Detection
 
 All ALPS touchpads should respond to the "E6 report" command sequence:
 E8-E6-E6-E6-E9. An ALPS touchpad should respond with either 00-00-0A or
-00-00-64.
+00-00-64 if no buttons are pressed. The bits 0-2 of the first byte will be 1s
+if some buttons are pressed.
 
 If the E6 report is successful, the touchpad model is identified using the "E7
 report" sequence: E8-E7-E7-E7-E9. The response is the model signature and is

drivers/input/mouse/alps.c

@@ -952,7 +952,9 @@ static const struct alps_model_info *alps_get_model(struct psmouse *psmouse, int
 
 	/*
 	 * First try "E6 report".
-	 * ALPS should return 0,0,10 or 0,0,100
+	 * ALPS should return 0,0,10 or 0,0,100 if no buttons are pressed.
+	 * The bits 0-2 of the first byte will be 1s if some buttons are
+	 * pressed.
 	 */
 	param[0] = 0;
 	if (ps2_command(ps2dev, param, PSMOUSE_CMD_SETRES) ||
@@ -968,7 +970,8 @@ static const struct alps_model_info *alps_get_model(struct psmouse *psmouse, int
 	psmouse_dbg(psmouse, "E6 report: %2.2x %2.2x %2.2x",
 		    param[0], param[1], param[2]);
 
-	if (param[0] != 0 || param[1] != 0 || (param[2] != 10 && param[2] != 100))
+	if ((param[0] & 0xf8) != 0 || param[1] != 0 ||
+	    (param[2] != 10 && param[2] != 100))
 		return NULL;
 
 	/*