Input: synaptics - refactor agm packet parsing

When a Synaptics touchpad is in "AGM" mode, and multiple fingers are
detected, the touchpad sends alternating "Advanced Gesture Mode" (AGM) and
"Simple Gesture Mode" (SGM) packets.
  The AGM packets have w=2, and contain reduced resolution finger data.
  The SGM packets have w={0,1} and contain full resolution finger data.

Refactor the parsing of agm packets to its own function, and rename the
synaptics_data.mt field to .agm to indicate that it contains the contents of
the last agm packet.

Signed-off-by: Daniel Kurtz <djkurtz@chromium.org>
Acked-by: Chase Douglas <chase.douglas@canonical.com>
Acked-by: Henrik Rydberg <rydberg@euromail.se>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

drivers/input/mouse/synaptics.c

@@ -419,6 +419,17 @@ static void synaptics_pt_create(struct psmouse *psmouse)
  *	Functions to interpret the absolute mode packets
  ****************************************************************************/
 
+static void synaptics_parse_agm(const unsigned char buf[],
+				struct synaptics_data *priv)
+{
+	struct synaptics_hw_state *agm = &priv->agm;
+
+	/* Gesture packet: (x, y, z) at half resolution */
+	agm->x = (((buf[4] & 0x0f) << 8) | buf[1]) << 1;
+	agm->y = (((buf[4] & 0xf0) << 4) | buf[2]) << 1;
+	agm->z = ((buf[3] & 0x30) | (buf[5] & 0x0f)) << 1;
+}
+
 static int synaptics_parse_hw_state(const unsigned char buf[],
 				    struct synaptics_data *priv,
 				    struct synaptics_hw_state *hw)
@@ -453,10 +464,7 @@ static int synaptics_parse_hw_state(const unsigned char buf[],
 		}
 
 		if (SYN_CAP_ADV_GESTURE(priv->ext_cap_0c) && hw->w == 2) {
-			/* Gesture packet: (x, y, z) at half resolution */
-			priv->mt.x = (((buf[4] & 0x0f) << 8) | buf[1]) << 1;
-			priv->mt.y = (((buf[4] & 0xf0) << 4) | buf[2]) << 1;
-			priv->mt.z = ((buf[3] & 0x30) | (buf[5] & 0x0f)) << 1;
+			synaptics_parse_agm(buf, priv);
 			return 1;
 		}
 
@@ -595,7 +603,8 @@ static void synaptics_process_packet(struct psmouse *psmouse)
 	}
 
 	if (SYN_CAP_ADV_GESTURE(priv->ext_cap_0c))
-		synaptics_report_semi_mt_data(dev, &hw, &priv->mt, num_fingers);
+		synaptics_report_semi_mt_data(dev, &hw, &priv->agm,
+					      num_fingers);
 
 	/* Post events
 	 * BTN_TOUCH has to be first as mousedev relies on it when doing

drivers/input/mouse/synaptics.h

@@ -146,7 +146,11 @@ struct synaptics_data {
 
 	struct serio *pt_port;			/* Pass-through serio port */
 
-	struct synaptics_hw_state mt;		/* current gesture packet */
+	/*
+	 * Last received Advanced Gesture Mode (AGM) packet. An AGM packet
+	 * contains position data for a second contact, at half resolution.
+	 */
+	struct synaptics_hw_state agm;
 };
 
 void synaptics_module_init(void);