HID: magicmouse: Implement Multi-touch Protocol B (MT-B)

The driver for Apple Magic Trackpad/Mouse currently uses
Multi-touch Protocol A (MT-A) to report touch events and uses
ABS_MT_TRACKING_ID to do finger tracking. The fact of the device
being able to track individual finger makes it possible to
report touch events using MT-B. This patch converts the driver
to use MT-B as it is preferred to MT-A.

V4: Removed BTN_TOUCH evnet.
V3: Removed the single touch related logic.
V2: Converting entirely to MT-B as Henrik Rydberg suggested.
Signed-off-by: Yufeng Shen <miletus@chromium.org>
Reviewed-and-tested-by: Henrik Rydberg <rydberg@euromail.se>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/hid-magicmouse.c

@@ -16,6 +16,7 @@
 
 #include <linux/device.h>
 #include <linux/hid.h>
+#include <linux/input/mt.h>
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/usb.h>
@@ -68,15 +69,6 @@ MODULE_PARM_DESC(report_undeciphered, "Report undeciphered multi-touch state fie
 
 #define SCROLL_ACCEL_DEFAULT 7
 
-/* Single touch emulation should only begin when no touches are currently down.
- * This is true when single_touch_id is equal to NO_TOUCHES. If multiple touches
- * are down and the touch providing for single touch emulation is lifted,
- * single_touch_id is equal to SINGLE_TOUCH_UP. While single touch emulation is
- * occurring, single_touch_id corresponds with the tracking id of the touch used.
- */
-#define NO_TOUCHES -1
-#define SINGLE_TOUCH_UP -2
-
 /* Touch surface information. Dimension is in hundredths of a mm, min and max
  * are in units. */
 #define MOUSE_DIMENSION_X (float)9056
@@ -125,7 +117,6 @@ struct magicmouse_sc {
 		u8 size;
 	} touches[16];
 	int tracking_ids[16];
-	int single_touch_id;
 };
 
 static int magicmouse_firm_touch(struct magicmouse_sc *msc)
@@ -264,16 +255,14 @@ static void magicmouse_emit_touch(struct magicmouse_sc *msc, int raw_id, u8 *tda
 		}
 	}
 
-	if (down) {
+	if (down)
 		msc->ntouches++;
-		if (msc->single_touch_id == NO_TOUCHES)
-			msc->single_touch_id = id;
-	} else if (msc->single_touch_id == id)
-		msc->single_touch_id = SINGLE_TOUCH_UP;
+
+	input_mt_slot(input, id);
+	input_mt_report_slot_state(input, MT_TOOL_FINGER, down);
 
 	/* Generate the input events for this touch. */
 	if (down) {
-		input_report_abs(input, ABS_MT_TRACKING_ID, id);
 		input_report_abs(input, ABS_MT_TOUCH_MAJOR, touch_major << 2);
 		input_report_abs(input, ABS_MT_TOUCH_MINOR, touch_minor << 2);
 		input_report_abs(input, ABS_MT_ORIENTATION, -orientation);
@@ -286,8 +275,6 @@ static void magicmouse_emit_touch(struct magicmouse_sc *msc, int raw_id, u8 *tda
 			else /* USB_DEVICE_ID_APPLE_MAGICTRACKPAD */
 				input_event(input, EV_MSC, MSC_RAW, tdata[8]);
 		}
-
-		input_mt_sync(input);
 	}
 }
 
@@ -308,12 +295,6 @@ static int magicmouse_raw_event(struct hid_device *hdev,
 		for (ii = 0; ii < npoints; ii++)
 			magicmouse_emit_touch(msc, ii, data + ii * 9 + 4);
 
-		/* We don't need an MT sync here because trackpad emits a
-		 * BTN_TOUCH event in a new frame when all touches are released.
-		 */
-		if (msc->ntouches == 0)
-			msc->single_touch_id = NO_TOUCHES;
-
 		clicks = data[1];
 
 		/* The following bits provide a device specific timestamp. They
@@ -331,9 +312,6 @@ static int magicmouse_raw_event(struct hid_device *hdev,
 		for (ii = 0; ii < npoints; ii++)
 			magicmouse_emit_touch(msc, ii, data + ii * 8 + 6);
 
-		if (msc->ntouches == 0)
-			input_mt_sync(input);
-
 		/* When emulating three-button mode, it is important
 		 * to have the current touch information before
 		 * generating a click event.
@@ -366,25 +344,17 @@ static int magicmouse_raw_event(struct hid_device *hdev,
 		input_report_rel(input, REL_Y, y);
 	} else { /* USB_DEVICE_ID_APPLE_MAGICTRACKPAD */
 		input_report_key(input, BTN_MOUSE, clicks & 1);
-		input_report_key(input, BTN_TOUCH, msc->ntouches > 0);
-		input_report_key(input, BTN_TOOL_FINGER, msc->ntouches == 1);
-		input_report_key(input, BTN_TOOL_DOUBLETAP, msc->ntouches == 2);
-		input_report_key(input, BTN_TOOL_TRIPLETAP, msc->ntouches == 3);
-		input_report_key(input, BTN_TOOL_QUADTAP, msc->ntouches == 4);
-		if (msc->single_touch_id >= 0) {
-			input_report_abs(input, ABS_X,
-				msc->touches[msc->single_touch_id].x);
-			input_report_abs(input, ABS_Y,
-				msc->touches[msc->single_touch_id].y);
-		}
+		input_mt_report_pointer_emulation(input, true);
 	}
 
 	input_sync(input);
 	return 1;
 }
 
-static void magicmouse_setup_input(struct input_dev *input, struct hid_device *hdev)
+static int magicmouse_setup_input(struct input_dev *input, struct hid_device *hdev)
 {
+	int error;
+
 	__set_bit(EV_KEY, input->evbit);
 
 	if (input->id.product == USB_DEVICE_ID_APPLE_MAGICMOUSE) {
@@ -413,6 +383,7 @@ static void magicmouse_setup_input(struct input_dev *input, struct hid_device *h
 		__set_bit(BTN_TOOL_DOUBLETAP, input->keybit);
 		__set_bit(BTN_TOOL_TRIPLETAP, input->keybit);
 		__set_bit(BTN_TOOL_QUADTAP, input->keybit);
+		__set_bit(BTN_TOOL_QUINTTAP, input->keybit);
 		__set_bit(BTN_TOUCH, input->keybit);
 		__set_bit(INPUT_PROP_POINTER, input->propbit);
 		__set_bit(INPUT_PROP_BUTTONPAD, input->propbit);
@@ -421,7 +392,9 @@ static void magicmouse_setup_input(struct input_dev *input, struct hid_device *h
 
 	__set_bit(EV_ABS, input->evbit);
 
-	input_set_abs_params(input, ABS_MT_TRACKING_ID, 0, 15, 0, 0);
+	error = input_mt_init_slots(input, 16);
+	if (error)
+		return error;
 	input_set_abs_params(input, ABS_MT_TOUCH_MAJOR, 0, 255 << 2,
 			     4, 0);
 	input_set_abs_params(input, ABS_MT_TOUCH_MINOR, 0, 255 << 2,
@@ -468,6 +441,8 @@ static void magicmouse_setup_input(struct input_dev *input, struct hid_device *h
 		__set_bit(EV_MSC, input->evbit);
 		__set_bit(MSC_RAW, input->mscbit);
 	}
+
+	return 0;
 }
 
 static int magicmouse_input_mapping(struct hid_device *hdev,
@@ -506,8 +481,6 @@ static int magicmouse_probe(struct hid_device *hdev,
 	msc->quirks = id->driver_data;
 	hid_set_drvdata(hdev, msc);
 
-	msc->single_touch_id = NO_TOUCHES;
-
 	ret = hid_parse(hdev);
 	if (ret) {
 		hid_err(hdev, "magicmouse hid parse failed\n");
@@ -523,8 +496,13 @@ static int magicmouse_probe(struct hid_device *hdev,
 	/* We do this after hid-input is done parsing reports so that
 	 * hid-input uses the most natural button and axis IDs.
 	 */
-	if (msc->input)
-		magicmouse_setup_input(msc->input, hdev);
+	if (msc->input) {
+		ret = magicmouse_setup_input(msc->input, hdev);
+		if (ret) {
+			hid_err(hdev, "magicmouse setup input failed (%d)\n", ret);
+			goto err_stop_hw;
+		}
+	}
 
 	if (id->product == USB_DEVICE_ID_APPLE_MAGICMOUSE)
 		report = hid_register_report(hdev, HID_INPUT_REPORT,