[PATCH 3/6] Input: elantech - packet checking for v2 hardware

[JJ Ding]

For v2 hardware, there is no real parity check, but we can still check
some constant bits for data integrity.

Signed-off-by: JJ Ding <jj_ding@xxxxxxxxxx>
---
 drivers/input/mouse/elantech.c |   26 +++++++++++++++++++++++---
 1 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/drivers/input/mouse/elantech.c b/drivers/input/mouse/elantech.c
index cf41f23..032181c 100644
--- a/drivers/input/mouse/elantech.c
+++ b/drivers/input/mouse/elantech.c
@@ -376,6 +376,25 @@ static int elantech_check_parity_v1(struct psmouse *psmouse)
 	       etd->parity[packet[3]] == p3;
 }
 
+static int packet_simple_check_v2(struct psmouse *psmouse)
+{
+	struct elantech_data *etd = psmouse->private;
+	unsigned char *packet = psmouse->packet;
+
+	if (etd->reports_pressure)
+		return (packet[0] & 0x0c) == 0x04 &&
+		       (packet[3] & 0x0f) == 0x02;
+
+	if ((packet[0] & 0xc0) == 0x80)
+		return (packet[0] & 0x0c) == 0x0c &&
+		       (packet[3] & 0x0e) == 0x08;
+
+	return (packet[0] & 0x3c) == 0x3c &&
+	       (packet[1] & 0xf0) == 0x00 &&
+	       (packet[3] & 0x3e) == 0x38 &&
+	       (packet[4] & 0xf0) == 0x00;
+}
+
 /*
  * Process byte stream from mouse and handle complete packets
  */
@@ -398,7 +417,9 @@ static psmouse_ret_t elantech_process_byte(struct psmouse *psmouse)
 		break;
 
 	case 2:
-		/* We don't know how to check parity in protocol v2 */
+		if (etd->paritycheck && !packet_simple_check_v2(psmouse))
+			return PSMOUSE_BAD_DATA;
+
 		elantech_report_absolute_v2(psmouse);
 		break;
 	}
@@ -799,8 +820,7 @@ int elantech_init(struct psmouse *psmouse)
 		etd->hw_version = 2;
 		/* For now show extra debug information */
 		etd->debug = 1;
-		/* Don't know how to do parity checking for version 2 */
-		etd->paritycheck = 0;
+		etd->paritycheck = 1;
 
 		if (etd->fw_version >= 0x020800)
 			etd->reports_pressure = true;
-- 
1.7.4.1

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