From: Benjamin Tissoires <benjamin.tissoi...@redhat.com>

Kernel tracking is used in 2 use cases:
- filter out jumps when the sensor is not relieable enough
- provide a MT protocol B when the sensor is providing MT protocol A data

Signed-off-by: Benjamin Tissoires <benjamin.tissoi...@redhat.com>
Tested-by: Andrew Duggan <adug...@synaptics.com>
---
 drivers/input/rmi4/rmi_f11.c | 153 +++++++++++++++++++++++++++++--------------
 include/linux/rmi.h          |  14 ++--
 2 files changed, 115 insertions(+), 52 deletions(-)

diff --git a/drivers/input/rmi4/rmi_f11.c b/drivers/input/rmi4/rmi_f11.c
index 02e3a6b..146691f 100644
--- a/drivers/input/rmi4/rmi_f11.c
+++ b/drivers/input/rmi4/rmi_f11.c
@@ -65,6 +65,9 @@
  * devices currently in the field.
  */
 
+/* maximum ABS_MT_POSITION displacement (in mm) */
+#define DMAX 10
+
 /**
  * @rezero - writing this to the F11 command register will cause the sensor to
  * calibrate to the current capacitive state.
@@ -497,9 +500,6 @@ struct f11_2d_data {
  * @data_pkt - buffer for data reported by this sensor.
  * @pkt_size - number of bytes in that buffer.
  * @sensor_index - identifies this particular 2D touch sensor
- * @type_a - some early RMI4 2D sensors do not reliably track the finger
- * position when two fingers are on the device.  When this is true, we
- * assume we have one of those sensors and report events appropriately.
  * @sensor_type - indicates whether we're touchscreen or touchpad.
  * @input - input device for absolute pointing stream
  * @input_phys - buffer for the absolute phys name for this sensor.
@@ -508,13 +508,16 @@ struct f11_2d_sensor {
        struct rmi_f11_2d_axis_alignment axis_align;
        struct f11_2d_sensor_queries sens_query;
        struct f11_2d_data data;
+       struct input_mt_pos *tracking_pos;
+       int *tracking_slots;
+       bool kernel_tracking;
+       int dmax;
        u16 max_x;
        u16 max_y;
        u8 nbr_fingers;
        u8 *data_pkt;
        int pkt_size;
        u8 sensor_index;
-       u32 type_a;     /* boolean but debugfs API requires u32 */
        bool topbuttonpad;
        enum rmi_f11_sensor_type sensor_type;
        struct input_dev *input;
@@ -604,6 +607,53 @@ static void rmi_f11_rel_pos_report(struct f11_2d_sensor 
*sensor, u8 n_finger)
        }
 }
 
+static void rmi_f11_abs_parse_xy(struct f11_data *f11,
+                                struct f11_2d_sensor *sensor,
+                                enum f11_finger_state finger_state,
+                                u8 n_finger)
+{
+       struct f11_2d_data *data = &sensor->data;
+       struct rmi_f11_2d_axis_alignment *axis_align = &sensor->axis_align;
+       u8 *pos_data = &data->abs_pos[n_finger * RMI_F11_ABS_BYTES];
+       u16 x, y;
+
+       /* we keep the previous values if the finger is released */
+       if (!finger_state)
+               return;
+
+       x = (pos_data[0] << 4) | (pos_data[2] & 0x0F);
+       y = (pos_data[1] << 4) | (pos_data[2] >> 4);
+
+       if (axis_align->swap_axes)
+               swap(x, y);
+
+       if (axis_align->flip_x)
+               x = max(sensor->max_x - x, 0);
+
+       if (axis_align->flip_y)
+               y = max(sensor->max_y - y, 0);
+
+       /*
+        * Here checking if X offset or y offset are specified is
+        * redundant. We just add the offsets or clip the values.
+        *
+        * Note: offsets need to be applied before clipping occurs,
+        * or we could get funny values that are outside of
+        * clipping boundaries.
+        */
+       x += axis_align->offset_x;
+       y += axis_align->offset_y;
+       x =  max(axis_align->clip_x_low, x);
+       y =  max(axis_align->clip_y_low, y);
+       if (axis_align->clip_x_high)
+               x = min(axis_align->clip_x_high, x);
+       if (axis_align->clip_y_high)
+               y =  min(axis_align->clip_y_high, y);
+
+       sensor->tracking_pos[n_finger].x = x;
+       sensor->tracking_pos[n_finger].y = y;
+}
+
 static void rmi_f11_abs_pos_report(struct f11_data *f11,
                                   struct f11_2d_sensor *sensor,
                                   enum f11_finger_state finger_state,
@@ -617,44 +667,16 @@ static void rmi_f11_abs_pos_report(struct f11_data *f11,
        int w_x, w_y, w_max, w_min, orient;
        int tool_type = rmi_f11_get_tool_type(sensor, finger_state);
 
-       if (sensor->type_a) {
-               input_report_abs(input, ABS_MT_TRACKING_ID, n_finger);
-               input_report_abs(input, ABS_MT_TOOL_TYPE, tool_type);
-       } else {
+       if (sensor->kernel_tracking)
+               input_mt_slot(input, sensor->tracking_slots[n_finger]);
+       else
                input_mt_slot(input, n_finger);
-               input_mt_report_slot_state(input, tool_type,
-                                          finger_state != F11_NO_FINGER);
-       }
+       input_mt_report_slot_state(input, tool_type,
+                                  finger_state != F11_NO_FINGER);
 
        if (finger_state) {
-               x = (pos_data[0] << 4) | (pos_data[2] & 0x0F);
-               y = (pos_data[1] << 4) | (pos_data[2] >> 4);
-
-               if (axis_align->swap_axes)
-                       swap(x, y);
-
-               if (axis_align->flip_x)
-                       x = max(sensor->max_x - x, 0);
-
-               if (axis_align->flip_y)
-                       y = max(sensor->max_y - y, 0);
-
-               /*
-                * Here checking if X offset or y offset are specified is
-                * redundant. We just add the offsets or clip the values.
-                *
-                * Note: offsets need to be applied before clipping occurs,
-                * or we could get funny values that are outside of
-                * clipping boundaries.
-                */
-               x += axis_align->offset_x;
-               y += axis_align->offset_y;
-               x =  max(axis_align->clip_x_low, x);
-               y =  max(axis_align->clip_y_low, y);
-               if (axis_align->clip_x_high)
-                       x = min(axis_align->clip_x_high, x);
-               if (axis_align->clip_y_high)
-                       y =  min(axis_align->clip_y_high, y);
+               x = sensor->tracking_pos[n_finger].x;
+               y = sensor->tracking_pos[n_finger].y;
 
                w_x = pos_data[3] & 0x0f;
                w_y = pos_data[3] >> 4;
@@ -690,10 +712,6 @@ static void rmi_f11_abs_pos_report(struct f11_data *f11,
                        "finger[%d]:%d - x:%d y:%d z:%d w_max:%d w_min:%d\n",
                        n_finger, finger_state, x, y, z, w_max, w_min);
        }
-
-       /* MT sync between fingers */
-       if (sensor->type_a)
-               input_mt_sync(input);
 }
 
 static inline u8 rmi_f11_parse_finger_state(const u8 *f_state, u8 n_finger)
@@ -724,13 +742,36 @@ static void rmi_f11_finger_handler(struct f11_data *f11,
                }
 
                if (abs_bits)
-                       rmi_f11_abs_pos_report(f11, sensor, finger_state, i);
+                       rmi_f11_abs_parse_xy(f11, sensor, finger_state, i);
 
                if (rel_bits)
                        rmi_f11_rel_pos_report(sensor, i);
        }
 
-       input_mt_sync_frame(sensor->input);
+       if (abs_bits) {
+               /*
+                * the absolute part is made in 2 parts to allow the kernel
+                * tracking to take place.
+                */
+               if (sensor->kernel_tracking)
+                       input_mt_assign_slots(sensor->input,
+                                             sensor->tracking_slots,
+                                             sensor->tracking_pos,
+                                             sensor->nbr_fingers,
+                                             sensor->dmax);
+
+               for (i = 0; i < sensor->nbr_fingers; i++) {
+                       finger_state = rmi_f11_parse_finger_state(f_state, i);
+                       if (finger_state == F11_RESERVED)
+                               /* no need to send twice the error */
+                               continue;
+
+                       rmi_f11_abs_pos_report(f11, sensor, finger_state, i);
+               }
+
+               input_mt_sync_frame(sensor->input);
+       }
+
        if (!sensor->unified_input)
                input_sync(sensor->input);
 }
@@ -1138,6 +1179,9 @@ static void f11_set_abs_params(struct rmi_function *fn, 
struct f11_data *f11)
        else
                input_flags = INPUT_MT_DIRECT;
 
+       if (sensor->kernel_tracking)
+               input_flags |= INPUT_MT_TRACK;
+
        if (sensor->axis_align.swap_axes) {
                int temp = device_x_max;
                device_x_max = device_y_max;
@@ -1189,10 +1233,12 @@ static void f11_set_abs_params(struct rmi_function *fn, 
struct f11_data *f11)
 
                input_abs_set_res(input, ABS_MT_POSITION_X, res_x);
                input_abs_set_res(input, ABS_MT_POSITION_Y, res_y);
+
+               if (!sensor->dmax)
+                       sensor->dmax = DMAX * res_x;
        }
 
-       if (!sensor->type_a)
-               input_mt_init_slots(input, sensor->nbr_fingers, input_flags);
+       input_mt_init_slots(input, sensor->nbr_fingers, input_flags);
        if (IS_ENABLED(CONFIG_RMI4_F11_PEN) && sensor->sens_query.has_pen)
                input_set_abs_params(input, ABS_MT_TOOL_TYPE,
                                     0, MT_TOOL_MAX, 0, 0);
@@ -1285,8 +1331,10 @@ static int rmi_f11_initialize(struct rmi_function *fn)
        if (pdata->f11_sensor_data) {
                sensor->axis_align =
                        pdata->f11_sensor_data->axis_align;
-               sensor->type_a = pdata->f11_sensor_data->type_a;
                sensor->topbuttonpad = pdata->f11_sensor_data->topbuttonpad;
+               sensor->kernel_tracking =
+                       pdata->f11_sensor_data->kernel_tracking;
+               sensor->dmax = pdata->f11_sensor_data->dmax;
 
                if (sensor->sens_query.has_physical_props) {
                        sensor->x_mm = sensor->sens_query.x_sensor_size_mm;
@@ -1336,6 +1384,15 @@ static int rmi_f11_initialize(struct rmi_function *fn)
        if (rc < 0)
                return rc;
 
+       /* allocate the in-kernel tracking buffers */
+       sensor->tracking_pos = devm_kzalloc(&fn->dev,
+                       sizeof(struct input_mt_pos) * sensor->nbr_fingers,
+                       GFP_KERNEL);
+       sensor->tracking_slots = devm_kzalloc(&fn->dev,
+                       sizeof(int) * sensor->nbr_fingers, GFP_KERNEL);
+       if (!sensor->tracking_pos || !sensor->tracking_slots)
+               return -ENOMEM;
+
        ctrl = &f11->dev_controls;
        if (sensor->axis_align.delta_x_threshold) {
                ctrl->ctrl0_9[RMI_F11_DELTA_X_THRESHOLD] =
diff --git a/include/linux/rmi.h b/include/linux/rmi.h
index 4ffe9fe..f270ff9 100644
--- a/include/linux/rmi.h
+++ b/include/linux/rmi.h
@@ -84,9 +84,6 @@ enum rmi_f11_sensor_type {
 /**
  * struct rmi_f11_sensor_data - overrides defaults for a single F11 2D sensor.
  * @axis_align - provides axis alignment overrides (see above).
- * @type_a - all modern RMI F11 firmwares implement Multifinger Type B
- * protocol.  Set this to true to force MF Type A behavior, in case you find
- * an older sensor.
  * @sensor_type - Forces the driver to treat the sensor as an indirect
  * pointing device (touchpad) rather than a direct pointing device
  * (touchscreen).  This is useful when F11_2D_QUERY14 register is not
@@ -95,15 +92,24 @@ enum rmi_f11_sensor_type {
  * by the firware.
  * @topbuttonpad - Used with the "5 buttons touchpads" found on the Lenovo 40
  * series
+ * @kernel_tracking - most moderns RMI f11 firmwares implement Multifinger
+ * Type B protocol. However, there are some corner cases where the user
+ * triggers some jumps by tapping with two fingers on the touchpad.
+ * Use this setting and dmax to filter out these jumps.
+ * Also, when using an old sensor using MF Type A behavior, set to true to
+ * report an actual MT protocol B.
+ * @dmax - the maximum distance (in sensor units) the kernel tracking allows 
two
+ * distincts fingers to be considered the same.
  */
 struct rmi_f11_sensor_data {
        struct rmi_f11_2d_axis_alignment axis_align;
-       bool type_a;
        enum rmi_f11_sensor_type sensor_type;
        int x_mm;
        int y_mm;
        int disable_report_mask;
        bool topbuttonpad;
+       bool kernel_tracking;
+       int dmax;
 };
 
 /**
-- 
2.1.4

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