hid: egalax: Add event filtering

Use estimated signal-to-noise ratios to reduce noise and limit the
amount of events emitted.

Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Cc: Stephane Chatty <chatty@enac.fr>
Signed-off-by: Henrik Rydberg <rydberg@euromail.se>

1 files changed, 10 insertions, 6 deletions

diff --git a/drivers/hid/hid-egalax.c b/drivers/hid/hid-egalax.c
index aac8a6326bbd..66b2c5d919af 100644
--- a/drivers/hid/hid-egalax.c
+++ b/drivers/hid/hid-egalax.c
@@ -25,6 +25,10 @@ MODULE_LICENSE("GPL");
 
 #include "hid-ids.h"
 
+/* estimated signal-to-noise ratios */
+#define SN_MOVE                 4096
+#define SN_PRESSURE             32
+
 struct egalax_data {
         __u16 x, y, z;
         __u8 id;
@@ -57,17 +61,17 @@ static int egalax_input_mapping(struct hid_device *hdev, struct hid_input *hi,
                         field->logical_maximum = 32760;
                         hid_map_usage(hi, usage, bit, max,
                                         EV_ABS, ABS_MT_POSITION_X);
-                        set_abs(input, ABS_MT_POSITION_X, field, 0);
+                        set_abs(input, ABS_MT_POSITION_X, field, SN_MOVE);
                         /* touchscreen emulation */
-                        set_abs(input, ABS_X, field, 0);
+                        set_abs(input, ABS_X, field, SN_MOVE);
                         return 1;
                 case HID_GD_Y:
                         field->logical_maximum = 32760;
                         hid_map_usage(hi, usage, bit, max,
                                         EV_ABS, ABS_MT_POSITION_Y);
-                        set_abs(input, ABS_MT_POSITION_Y, field, 0);
+                        set_abs(input, ABS_MT_POSITION_Y, field, SN_MOVE);
                         /* touchscreen emulation */
-                        set_abs(input, ABS_Y, field, 0);
+                        set_abs(input, ABS_Y, field, SN_MOVE);
                         return 1;
                 }
                 return 0;
@@ -93,9 +97,9 @@ static int egalax_input_mapping(struct hid_device *hdev, struct hid_input *hi,
                         field->logical_minimum = 0;
                         hid_map_usage(hi, usage, bit, max,
                                         EV_ABS, ABS_MT_PRESSURE);
-                        set_abs(input, ABS_MT_PRESSURE, field, 0);
+                        set_abs(input, ABS_MT_PRESSURE, field, SN_PRESSURE);
                         /* touchscreen emulation */
-                        set_abs(input, ABS_PRESSURE, field, 0);
+                        set_abs(input, ABS_PRESSURE, field, SN_PRESSURE);
                         return 1;
                 }
                 return 0;