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

[Yufeng Shen <miletus@chromium.org>]

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 adds the support
for the driver to report MT-B and makes it configurable through
module parameter so that existing codes that are relying on its
MT-A implemtation don't get affected.

Signed-off-by: Yufeng Shen <miletus@chromium.org>
---
 drivers/hid/hid-magicmouse.c |   29 ++++++++++++++++++++++++-----
 1 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/drivers/hid/hid-magicmouse.c b/drivers/hid/hid-magicmouse.c
index 40ac665..18d1ea0 100644
--- a/drivers/hid/hid-magicmouse.c
+++ b/drivers/hid/hid-magicmouse.c
@@ -17,6 +17,7 @@
 #include <linux/device.h>
 #include <linux/hid.h>
 #include <linux/module.h>
+#include <linux/input/mt.h>
 #include <linux/slab.h>
 #include <linux/usb.h>
 
@@ -56,6 +57,10 @@ static bool report_undeciphered;
 module_param(report_undeciphered, bool, 0644);
 MODULE_PARM_DESC(report_undeciphered, "Report undeciphered multi-touch state field using a MSC_RAW event");
 
+static bool use_MTB;
+module_param(use_MTB, bool, 0644);
+MODULE_PARM_DESC(use_MTB, "Whether using MT-B protocol to report touch events");
+
 #define TRACKPAD_REPORT_ID 0x28
 #define MOUSE_REPORT_ID    0x29
 #define DOUBLE_REPORT_ID   0xf7
@@ -275,9 +280,18 @@ static void magicmouse_emit_touch(struct magicmouse_sc *msc, int raw_id, u8 *tda
 	} else if (msc->single_touch_id == id)
 		msc->single_touch_id = SINGLE_TOUCH_UP;
 
+	if (!report_touches)
+		return;
+
+	if (use_MTB) {
+		input_mt_slot(input, id);
+		input_mt_report_slot_state(input, MT_TOOL_FINGER, down);
+	}
+
 	/* Generate the input events for this touch. */
-	if (report_touches && down) {
-		input_report_abs(input, ABS_MT_TRACKING_ID, id);
+	if (down) {
+		if (!use_MTB)
+			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);
@@ -290,8 +304,8 @@ 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);
+		if (!use_MTB)
+			input_mt_sync(input);
 	}
 }
 
@@ -425,7 +439,12 @@ static void magicmouse_setup_input(struct input_dev *input, struct hid_device *h
 	if (report_touches) {
 		__set_bit(EV_ABS, input->evbit);
 
-		input_set_abs_params(input, ABS_MT_TRACKING_ID, 0, 15, 0, 0);
+		if (use_MTB)
+			input_mt_init_slots(input, 16);
+		else
+			input_set_abs_params(input, ABS_MT_TRACKING_ID, 0, 15,
+					     0, 0);
+
 		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,
-- 
1.7.7.3