Input: ALPS - allow touchsticks to report pressure

BugLink: http://bugs.launchpad.net/bugs/1571530

The SS5 hardware can report this.
Tested-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Ben Gamari <ben@smart-cactus.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
(cherry picked from commit 7ad8a106)
Signed-off-by: Phidias Chiang <phidias.chiang@canonical.com>
Acked-by: Tim Gardner <tim.gardner@canonical.com>
Acked-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

drivers/input/mouse/alps.c

@@ -102,6 +102,7 @@ static const struct alps_nibble_commands alps_v6_nibble_commands[] = {
 					   6-byte ALPS packet */
 #define ALPS_STICK_BITS		0x100	/* separate stick button bits */
 #define ALPS_BUTTONPAD		0x200	/* device is a clickpad */
+#define ALPS_DUALPOINT_WITH_PRESSURE	0x400	/* device can report trackpoint pressure */
 
 static const struct alps_model_info alps_model_data[] = {
 	{ { 0x32, 0x02, 0x14 }, 0x00, { ALPS_PROTO_V2, 0xf8, 0xf8, ALPS_PASS | ALPS_DUALPOINT } },	/* Toshiba Salellite Pro M10 */
@@ -1271,9 +1272,11 @@ static int alps_decode_ss4_v2(struct alps_fields *f,
 		} else {
 			int x = (s8)(((p[0] & 1) << 7) | (p[1] & 0x7f));
 			int y = (s8)(((p[3] & 1) << 7) | (p[2] & 0x7f));
+			int pressure = (s8)(p[4] & 0x7f);
 
 			input_report_rel(priv->dev2, REL_X, x);
 			input_report_rel(priv->dev2, REL_Y, -y);
+			input_report_abs(priv->dev2, ABS_PRESSURE, pressure);
 		}
 		break;
 
@@ -2992,6 +2995,10 @@ int alps_init(struct psmouse *psmouse)
 
 		input_set_capability(dev2, EV_REL, REL_X);
 		input_set_capability(dev2, EV_REL, REL_Y);
+		if (priv->flags & ALPS_DUALPOINT_WITH_PRESSURE) {
+			input_set_capability(dev2, EV_ABS, ABS_PRESSURE);
+			input_set_abs_params(dev2, ABS_PRESSURE, 0, 127, 0, 0);
+		}
 		input_set_capability(dev2, EV_KEY, BTN_LEFT);
 		input_set_capability(dev2, EV_KEY, BTN_RIGHT);
 		input_set_capability(dev2, EV_KEY, BTN_MIDDLE);