Input: synaptics - use firmware data for Cr-48

The profile sensor clickpad in a Cr-48 Chromebook does a reasonable job
of tracking individual fingers. This tracking isn't perfect, but,
experiments show that it works better than just passing "semi-mt" data
to userspace, and making userspace try to deduce where the fingers are
given a bounding box.

This patch tries to report correct two-finger positions instead of the
{(min_x, min_y), (max_x, max_y)} for profile sensor clickpads on Cr-48
chromebooks. Note that this device's firmware always reports the higher
(smaller y) finger in the "sgm" packet, and the lower (larger y) finger
in the "agm" packet. Thus, when a new finger arrives on the pad, the
kernel driver uses input core's contact tracking facilities to match
contacts with slots.

Inspired by patch by Daniel Kurtz <djkurtz@chromium.org> and Chung-yih
Wang <cywang@chromium.org>

Signed-off-by: Henrik Rydberg <rydberg@euromail.se>
Reviewed-by: Benson Leung <bleung@chromium.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/mouse/synaptics.c

@@ -117,6 +117,9 @@ void synaptics_reset(struct psmouse *psmouse)
 }
 
 #ifdef CONFIG_MOUSE_PS2_SYNAPTICS
+
+static bool cr48_profile_sensor;
+
 struct min_max_quirk {
 	const char * const *pnp_ids;
 	int x_min, x_max, y_min, y_max;
@@ -1151,6 +1154,42 @@ static void synaptics_image_sensor_process(struct psmouse *psmouse,
 	priv->agm_pending = false;
 }
 
+static void synaptics_profile_sensor_process(struct psmouse *psmouse,
+					     struct synaptics_hw_state *sgm,
+					     int num_fingers)
+{
+	struct input_dev *dev = psmouse->dev;
+	struct synaptics_data *priv = psmouse->private;
+	struct synaptics_hw_state *hw[2] = { sgm, &priv->agm };
+	struct input_mt_pos pos[2];
+	int slot[2], nsemi, i;
+
+	nsemi = clamp_val(num_fingers, 0, 2);
+
+	for (i = 0; i < nsemi; i++) {
+		pos[i].x = hw[i]->x;
+		pos[i].y = synaptics_invert_y(hw[i]->y);
+	}
+
+	input_mt_assign_slots(dev, slot, pos, nsemi);
+
+	for (i = 0; i < nsemi; i++) {
+		input_mt_slot(dev, slot[i]);
+		input_mt_report_slot_state(dev, MT_TOOL_FINGER, true);
+		input_report_abs(dev, ABS_MT_POSITION_X, pos[i].x);
+		input_report_abs(dev, ABS_MT_POSITION_Y, pos[i].y);
+		input_report_abs(dev, ABS_MT_PRESSURE, hw[i]->z);
+	}
+
+	input_mt_drop_unused(dev);
+	input_mt_report_pointer_emulation(dev, false);
+	input_mt_report_finger_count(dev, num_fingers);
+
+	synaptics_report_buttons(psmouse, sgm);
+
+	input_sync(dev);
+}
+
 /*
  *  called for each full received packet from the touchpad
  */
@@ -1214,6 +1253,11 @@ static void synaptics_process_packet(struct psmouse *psmouse)
 		finger_width = 0;
 	}
 
+	if (cr48_profile_sensor) {
+		synaptics_profile_sensor_process(psmouse, &hw, num_fingers);
+		return;
+	}
+
 	if (SYN_CAP_ADV_GESTURE(priv->ext_cap_0c))
 		synaptics_report_semi_mt_data(dev, &hw, &priv->agm,
 					      num_fingers);
@@ -1359,6 +1403,9 @@ static void set_input_params(struct psmouse *psmouse,
 	set_abs_position_params(dev, priv, ABS_X, ABS_Y);
 	input_set_abs_params(dev, ABS_PRESSURE, 0, 255, 0, 0);
 
+	if (cr48_profile_sensor)
+		input_set_abs_params(dev, ABS_MT_PRESSURE, 0, 255, 0, 0);
+
 	if (SYN_CAP_IMAGE_SENSOR(priv->ext_cap_0c)) {
 		set_abs_position_params(dev, priv, ABS_MT_POSITION_X,
 					ABS_MT_POSITION_Y);
@@ -1372,9 +1419,14 @@ static void set_input_params(struct psmouse *psmouse,
 	} else if (SYN_CAP_ADV_GESTURE(priv->ext_cap_0c)) {
 		set_abs_position_params(dev, priv, ABS_MT_POSITION_X,
 					ABS_MT_POSITION_Y);
-		/* Non-image sensors with AGM use semi-mt */
+		/*
+		 * Profile sensor in CR-48 tracks contacts reasonably well,
+		 * other non-image sensors with AGM use semi-mt.
+		 */
 		input_mt_init_slots(dev, 2,
-				    INPUT_MT_POINTER | INPUT_MT_SEMI_MT);
+				    INPUT_MT_POINTER |
+				    (cr48_profile_sensor ?
+					INPUT_MT_TRACK : INPUT_MT_SEMI_MT));
 	}
 
 	if (SYN_CAP_PALMDETECT(priv->capabilities))
@@ -1576,10 +1628,24 @@ static const struct dmi_system_id olpc_dmi_table[] __initconst = {
 	{ }
 };
 
+static const struct dmi_system_id __initconst cr48_dmi_table[] = {
+#if defined(CONFIG_DMI) && defined(CONFIG_X86)
+	{
+		/* Cr-48 Chromebook (Codename Mario) */
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "IEC"),
+			DMI_MATCH(DMI_PRODUCT_NAME, "Mario"),
+		},
+	},
+#endif
+	{ }
+};
+
 void __init synaptics_module_init(void)
 {
 	impaired_toshiba_kbc = dmi_check_system(toshiba_dmi_table);
 	broken_olpc_ec = dmi_check_system(olpc_dmi_table);
+	cr48_profile_sensor = dmi_check_system(cr48_dmi_table);
 }
 
 static int __synaptics_init(struct psmouse *psmouse, bool absolute_mode)