[RESEND patch 2.6.22-rc4] ads7846 pendown status check

[David Brownell <david-b@pacbell.net>]

From: Semih Hazar <semih.hazar@indefia.com> 

Pendown status from the PENIRQ pin is currently read only at the beginning
of a sample set. If the pen is lifted just after sampling has began then
sampled values become wrong.

This patch adds an optional platform penirq_recheck_delay attribute.  If
non-zero, samples are only reported to the input subsystem if PENIRQ is
still active that long after the samples taken.

Signed-off-by: Semih Hazar <semih.hazar@indefia.com> 
Cc: Imre Deak <imre.deak@solidboot.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
---
Still applies fine against 2.6.22-git ... this should be in 2.6.23

 drivers/input/touchscreen/ads7846.c |   15 +++++++++++++++
 include/linux/spi/ads7846.h         |    6 ++++++
 2 files changed, 21 insertions(+)

--- g26.orig/include/linux/spi/ads7846.h	2007-06-16 04:33:43.000000000 -0700
+++ g26/include/linux/spi/ads7846.h	2007-06-16 09:46:32.000000000 -0700
@@ -24,6 +24,12 @@ struct ads7846_platform_data {
 	 */
 	u16	settle_delay_usecs;
 
+	/* If set to non-zero, after samples are taken this delay is applied
+	 * and penirq is rechecked, to help avoid false events.  This value
+	 * is affected by the material used to build the touch layer.
+	 */
+	u16	penirq_recheck_delay_usecs;
+
 	u16	x_plate_ohms;
 	u16	y_plate_ohms;
 
--- g26.orig/drivers/input/touchscreen/ads7846.c	2007-06-16 09:46:22.000000000 -0700
+++ g26/drivers/input/touchscreen/ads7846.c	2007-06-16 09:46:32.000000000 -0700
@@ -107,6 +107,8 @@ struct ads7846 {
 	u16			debounce_tol;
 	u16			debounce_rep;
 
+	u16			penirq_recheck_delay_usecs;
+
 	spinlock_t		lock;
 	struct hrtimer		timer;
 	unsigned		pendown:1;	/* P: lock */
@@ -553,6 +555,15 @@ static void ads7846_rx(void *ads)
 		return;
 	}
 
+	/* Maybe check the pendown state before reporting. This discards
+	 * false readings when the pen is lifted.
+	 */
+	if (ts->penirq_recheck_delay_usecs) {
+		udelay(ts->penirq_recheck_delay_usecs);
+		if (!ts->get_pendown_state())
+			Rt = 0;
+	}
+
 	/* NOTE: We can't rely on the pressure to determine the pen down
 	 * state, even this controller has a pressure sensor.  The pressure
 	 * value can fluctuate for quite a while after lifting the pen and
@@ -896,6 +907,10 @@ static int __devinit ads7846_probe(struc
 		ts->filter = ads7846_no_filter;
 	ts->get_pendown_state = pdata->get_pendown_state;
 
+	if (pdata->penirq_recheck_delay_usecs)
+		ts->penirq_recheck_delay_usecs =
+				pdata->penirq_recheck_delay_usecs;
+
 	snprintf(ts->phys, sizeof(ts->phys), "%s/input0", spi->dev.bus_id);
 
 	input_dev->name = "ADS784x Touchscreen";