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

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Op 18-08-11 03:57, JJ Ding schreef:
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>
If you add some comments, as suggest by Dmitry, it looks perfect :-)

Signed-off-by: Éric Piel <eric.piel@xxxxxxxxxxxxxxxx>

Éric

---
  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;
--
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