ads7846: filtering based on pressure value

Limit the pressure value to the maximum specified in the board-
specific file. Samples with pressure values beyond the maximum are
considered non-reliable. Report the previously measured X and Y
values samples instead of the non-reliable ones.
Signed-off-by: Imre Deak <imre.deak@nokia.com>
Signed-off-by: Juha Yrjola <juha.yrjola@nokia.com>

drivers/input/touchscreen/ads7846.c

@@ -80,10 +80,14 @@ struct ads7846 {
 	u16			model;
 	u16			vref_delay_usecs;
 	u16			x_plate_ohms;
+	u16			pressure_max;
 
 	u8			read_x, read_y, read_z1, read_z2, pwrdown;
 	u16			dummy;		/* for the pwrdown read */
 	struct ts_event		tc;
+	u16			last_x;
+	u16			last_y;
+	u16			last_pressure;
 
 	struct spi_transfer	xfer[10];
 	struct spi_message	msg[5];
@@ -344,6 +348,18 @@ static void ads7846_rx(void *ads)
 	} else
 		Rt = 0;
 
+	if (Rt > ts->pressure_max) {
+		if (ts->last_pressure) {
+			x = ts->last_x;
+			y = ts->last_y;
+		}
+		Rt = ts->pressure_max;
+	}
+
+	ts->last_x = x;
+	ts->last_y = y;
+	ts->last_pressure = Rt;
+
 	/* NOTE:  "pendown" is inferred from pressure; we don't rely on
 	 * being able to check nPENIRQ status, or "friendly" trigger modes
 	 * (both-edges is much better than just-falling or low-level).
@@ -593,6 +609,7 @@ static int __devinit ads7846_probe(struct spi_device *spi)
 	ts->model = pdata->model ? : 7846;
 	ts->vref_delay_usecs = pdata->vref_delay_usecs ? : 100;
 	ts->x_plate_ohms = pdata->x_plate_ohms ? : 400;
+	ts->pressure_max = pdata->pressure_max ? : ~0;
 	ts->debounce_max = pdata->debounce_max ? : 1;
 	ts->debounce_tol = pdata->debounce_tol ? : 10;