Input: appletouch - verious updates for MacBooks
Change a bit the finger detection method used by the appletouch
driver to reduce touchpad "jumpiness":
- Adjust the method for detecting multiple fingers. Previously, it
recognized a new finger when a low sensor reading is followed by
a high sensor reading. The new method checks for 'humps' in the
sensor readings, so there doesn't necessarily have to be a low
sensor between two high sensors for two fingers to be triggered.
This allows detecting presence of two fingers on the touchpad
even when they touch each other.
- Change absolute coordinate calculation to us to get rid of "jumps".
Instead of using full value from a sensor once it passes the
threshold subtract theshold value from the reading.
- Allow adjusting threshold value via module parameter.
The patch doesn't seem to affect the Powerbooks but does greatly improve
the touchpad behaviour on the MacBooks.
Signed-off-by: Jason Parekh <jasonparekh@gmail.com>
Signed-off-by: Stelian Pop <stelian@popies.net>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
diff --git a/drivers/usb/input/appletouch.c b/drivers/usb/input/appletouch.c
index 4c21351..4825db4 100644
--- a/drivers/usb/input/appletouch.c
+++ b/drivers/usb/input/appletouch.c
@@ -154,6 +154,13 @@
MODULE_DESCRIPTION("Apple PowerBooks USB touchpad driver");
MODULE_LICENSE("GPL");
+/*
+ * Make the threshold a module parameter
+ */
+static int threshold = ATP_THRESHOLD;
+module_param(threshold, int, 0644);
+MODULE_PARM_DESC(threshold, "Discards any change in data from a sensor (trackpad has hundreds of these sensors) less than this value");
+
static int debug = 1;
module_param(debug, int, 0644);
MODULE_PARM_DESC(debug, "Activate debugging output");
@@ -183,16 +190,48 @@
int i;
/* values to calculate mean */
int pcum = 0, psum = 0;
+ int is_increasing = 0;
*fingers = 0;
for (i = 0; i < nb_sensors; i++) {
- if (xy_sensors[i] < ATP_THRESHOLD)
+ if (xy_sensors[i] < threshold) {
+ if (is_increasing)
+ is_increasing = 0;
+
continue;
- if ((i - 1 < 0) || (xy_sensors[i - 1] < ATP_THRESHOLD))
+ }
+
+ /*
+ * Makes the finger detection more versatile. For example,
+ * two fingers with no gap will be detected. Also, my
+ * tests show it less likely to have intermittent loss
+ * of multiple finger readings while moving around (scrolling).
+ *
+ * Changes the multiple finger detection to counting humps on
+ * sensors (transitions from nonincreasing to increasing)
+ * instead of counting transitions from low sensors (no
+ * finger reading) to high sensors (finger above
+ * sensor)
+ *
+ * - Jason Parekh <jasonparekh@gmail.com>
+ */
+ if (i < 1 || (!is_increasing && xy_sensors[i - 1] < xy_sensors[i])) {
(*fingers)++;
- pcum += xy_sensors[i] * i;
- psum += xy_sensors[i];
+ is_increasing = 1;
+ } else if (i > 0 && xy_sensors[i - 1] >= xy_sensors[i]) {
+ is_increasing = 0;
+ }
+
+ /*
+ * Subtracts threshold so a high sensor that just passes the threshold
+ * won't skew the calculated absolute coordinate. Fixes an issue
+ * where slowly moving the mouse would occassionaly jump a number of
+ * pixels (let me restate--slowly moving the mouse makes this issue
+ * most apparent).
+ */
+ pcum += (xy_sensors[i] - threshold) * i;
+ psum += (xy_sensors[i] - threshold);
}
if (psum > 0) {