[PATCH v2 4/4] Input: zforce_ts: Add support for minimum touch size limit

[Dirk Behme <dirk.behme@de.bosch.com>]

From: Knut Wohlrab <Knut.Wohlrab@de.bosch.com>

The minimum touch size can be set to support more reliable touch
detection under difficult conditions (e.g. dust on touch panel surface).

For usage details see documentation.

Signed-off-by: Knut Wohlrab <Knut.Wohlrab@de.bosch.com>
Signed-off-by: Oleksij Rempel <linux@rempel-privat.de>
---
 .../bindings/input/touchscreen/zforce_ts.txt       |  2 ++
 drivers/input/touchscreen/zforce_ts.c              | 29 ++++++++++++++++++++++
 include/linux/platform_data/zforce_ts.h            |  1 +
 3 files changed, 32 insertions(+)

diff --git a/Documentation/devicetree/bindings/input/touchscreen/zforce_ts.txt b/Documentation/devicetree/bindings/input/touchscreen/zforce_ts.txt
index d8d57ba..60dd78b 100644
--- a/Documentation/devicetree/bindings/input/touchscreen/zforce_ts.txt
+++ b/Documentation/devicetree/bindings/input/touchscreen/zforce_ts.txt
@@ -13,6 +13,7 @@ Optional properties:
 - vdd-supply: Regulator controlling the controller supply
 - scan-idle-hz: idle scanning frequency in Hz (0 - 65535 Hz; default 10 Hz)
 - scan-active-hz: touch scanning frequeny in Hz (0 - 65535 Hz; default 50 Hz)
+- touch-size-min: minimun touch size limit in mm (0 - 255 mm; 0 = no limit (default))
 
 Example:
 
@@ -32,6 +33,7 @@ Example:
 			y-size = <600>;
 			scan-idle-hz = <50>;
 			scan-active-hz = <250>;
+			touch-size-min = <5>;
 		};
 
 		/* ... */
diff --git a/drivers/input/touchscreen/zforce_ts.c b/drivers/input/touchscreen/zforce_ts.c
index 2a818d4..99fe7b6 100644
--- a/drivers/input/touchscreen/zforce_ts.c
+++ b/drivers/input/touchscreen/zforce_ts.c
@@ -54,6 +54,7 @@
 #define COMMAND_SETCONFIG	0x03
 #define COMMAND_DATAREQUEST	0x04
 #define COMMAND_SCANFREQ	0x08
+#define COMMAND_TOUCH_SIZE	0x09
 #define COMMAND_STATUS		0X1e
 
 /*
@@ -65,6 +66,7 @@
 #define RESPONSE_RESOLUTION	0x02
 #define RESPONSE_SETCONFIG	0x03
 #define RESPONSE_SCANFREQ	0x08
+#define RESPONSE_TOUCH_SIZE	0x09
 #define RESPONSE_STATUS		0X1e
 
 /*
@@ -276,6 +278,21 @@ static int zforce_scan_frequency(struct zforce_ts *ts, u16 idle, u16 finger,
 	return zforce_send_wait(ts, &buf[0], ARRAY_SIZE(buf));
 }
 
+static int zforce_touch_size_limit(struct zforce_ts *ts, u8 limit)
+{
+	struct i2c_client *client = ts->client;
+	u8 buf[] = { FRAME_START, 5, COMMAND_TOUCH_SIZE,
+		     0, 0, /* maximum size limit off */
+		     1, limit }; /* set minimum size limit */
+
+	if (!limit)
+		return 0;
+
+	dev_dbg(&client->dev, "set min. touch size limit to %d mm\n", limit);
+
+	return zforce_send_wait(ts, &buf[0], ARRAY_SIZE(buf));
+}
+
 static int zforce_setconfig(struct zforce_ts *ts, char b1)
 {
 	struct i2c_client *client = ts->client;
@@ -316,6 +333,13 @@ static int zforce_start(struct zforce_ts *ts)
 		goto error;
 	}
 
+	ret = zforce_touch_size_limit(ts, pdata->touch_size_min);
+	if (ret) {
+		dev_err(&client->dev, "Unable to set min. touch size, %d\n",
+			ret);
+		goto error;
+	}
+
 	ret = zforce_setconfig(ts, SETCONFIG_DUALTOUCH);
 	if (ret) {
 		dev_err(&client->dev, "Unable to set config\n");
@@ -577,6 +601,7 @@ static irqreturn_t zforce_irq_thread(int irq, void *dev_id)
 		case RESPONSE_SETCONFIG:
 		case RESPONSE_RESOLUTION:
 		case RESPONSE_SCANFREQ:
+		case RESPONSE_TOUCH_SIZE:
 			zforce_complete(ts, payload[RESPONSE_ID],
 					payload[RESPONSE_DATA]);
 			break;
@@ -852,6 +877,10 @@ static struct zforce_ts_platdata *zforce_parse_dt(struct device *dev)
 				 &pdata->scan_freq_finger))
 		pdata->scan_freq_finger = SCAN_FREQ_DEFAULT_FINGER;
 
+	if (of_property_read_u8(np, "touch-size-min",
+				&pdata->touch_size_min))
+		pdata->touch_size_min = 0;
+
 	return pdata;
 }
 
diff --git a/include/linux/platform_data/zforce_ts.h b/include/linux/platform_data/zforce_ts.h
index 90a1181..75e1a49 100644
--- a/include/linux/platform_data/zforce_ts.h
+++ b/include/linux/platform_data/zforce_ts.h
@@ -20,6 +20,7 @@ struct zforce_ts_platdata {
 	unsigned int y_max;
 	u16 scan_freq_idle;
 	u16 scan_freq_finger;
+	u8 touch_size_min;
 };
 
 #endif /* _LINUX_INPUT_ZFORCE_TS_H */
-- 
1.9.1