Input: psmouse - expose drift duration for IBM trackpoints

IBM Trackpoints have a feature to compensate for drift by recalibrating
themselves periodically. By default, if for 0.5 seconds there is no change
in position, it's used as the new zero. This duration is too low. Often,
the calibration happens when the trackpoint is in fact being used.

IBM's Trackpoint Engineering Specifications show a configuration register
that allows changing this duration, rstdft1.

Expose it via sysfs among the other settings.
Signed-off-by: Mike Murdoch <main.haarp@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/mouse/trackpoint.c

@@ -227,6 +227,7 @@ TRACKPOINT_INT_ATTR(thresh, TP_THRESH, TP_DEF_THRESH);
 TRACKPOINT_INT_ATTR(upthresh, TP_UP_THRESH, TP_DEF_UP_THRESH);
 TRACKPOINT_INT_ATTR(ztime, TP_Z_TIME, TP_DEF_Z_TIME);
 TRACKPOINT_INT_ATTR(jenks, TP_JENKS_CURV, TP_DEF_JENKS_CURV);
+TRACKPOINT_INT_ATTR(drift_time, TP_DRIFT_TIME, TP_DEF_DRIFT_TIME);
 
 TRACKPOINT_BIT_ATTR(press_to_select, TP_TOGGLE_PTSON, TP_MASK_PTSON, 0,
 		    TP_DEF_PTSON);
@@ -246,6 +247,7 @@ static struct attribute *trackpoint_attrs[] = {
 	&psmouse_attr_upthresh.dattr.attr,
 	&psmouse_attr_ztime.dattr.attr,
 	&psmouse_attr_jenks.dattr.attr,
+	&psmouse_attr_drift_time.dattr.attr,
 	&psmouse_attr_press_to_select.dattr.attr,
 	&psmouse_attr_skipback.dattr.attr,
 	&psmouse_attr_ext_dev.dattr.attr,
@@ -312,6 +314,7 @@ static int trackpoint_sync(struct psmouse *psmouse, bool in_power_on_state)
 	TRACKPOINT_UPDATE(in_power_on_state, psmouse, tp, upthresh);
 	TRACKPOINT_UPDATE(in_power_on_state, psmouse, tp, ztime);
 	TRACKPOINT_UPDATE(in_power_on_state, psmouse, tp, jenks);
+	TRACKPOINT_UPDATE(in_power_on_state, psmouse, tp, drift_time);
 
 	/* toggles */
 	TRACKPOINT_UPDATE(in_power_on_state, psmouse, tp, press_to_select);
@@ -332,6 +335,7 @@ static void trackpoint_defaults(struct trackpoint_data *tp)
 	TRACKPOINT_SET_POWER_ON_DEFAULT(tp, upthresh);
 	TRACKPOINT_SET_POWER_ON_DEFAULT(tp, ztime);
 	TRACKPOINT_SET_POWER_ON_DEFAULT(tp, jenks);
+	TRACKPOINT_SET_POWER_ON_DEFAULT(tp, drift_time);
 	TRACKPOINT_SET_POWER_ON_DEFAULT(tp, inertia);
 
 	/* toggles */

drivers/input/mouse/trackpoint.h

@@ -70,6 +70,9 @@
 #define TP_UP_THRESH		0x5A	/* Used to generate a 'click' on Z-axis */
 #define TP_Z_TIME		0x5E	/* How sharp of a press */
 #define TP_JENKS_CURV		0x5D	/* Minimum curvature for double click */
+#define TP_DRIFT_TIME		0x5F	/* How long a 'hands off' condition */
+					/* must last (x*107ms) for drift */
+					/* correction to occur */
 
 /*
  * Toggling Flag bits
@@ -120,6 +123,7 @@
 #define TP_DEF_UP_THRESH	0xFF
 #define TP_DEF_Z_TIME		0x26
 #define TP_DEF_JENKS_CURV	0x87
+#define TP_DEF_DRIFT_TIME	0x05
 
 /* Toggles */
 #define TP_DEF_MB		0x00
@@ -137,6 +141,7 @@ struct trackpoint_data
 	unsigned char draghys, mindrag;
 	unsigned char thresh, upthresh;
 	unsigned char ztime, jenks;
+	unsigned char drift_time;
 
 	/* toggles */
 	unsigned char press_to_select;