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Subject[PATCH v4 5/8] Input: elantech - packet checking for v2 hardware
Date
For v2 hardware, there is no real parity check, but we can still check
some constant bits for data integrity.

Also rename elantech_check_parity_v1 to elantech_packet_check_v1 to make
these packet checking function names consistent.

Signed-off-by: JJ Ding <jj_ding@emc.com.tw>
Acked-by: Daniel Kurtz <djkurtz@chromium.org>
---
drivers/input/mouse/elantech.c | 39 ++++++++++++++++++++++++++++++++++-----
1 files changed, 34 insertions(+), 5 deletions(-)
diff --git a/drivers/input/mouse/elantech.c b/drivers/input/mouse/elantech.c
index 282b8b6..008e8c2 100644
--- a/drivers/input/mouse/elantech.c
+++ b/drivers/input/mouse/elantech.c
@@ -350,7 +350,7 @@ static void elantech_report_absolute_v2(struct psmouse *psmouse)
input_sync(dev);
}

-static int elantech_check_parity_v1(struct psmouse *psmouse)
+static int elantech_packet_check_v1(struct psmouse *psmouse)
{
struct elantech_data *etd = psmouse->private;
unsigned char *packet = psmouse->packet;
@@ -374,6 +374,34 @@ static int elantech_check_parity_v1(struct psmouse *psmouse)
etd->parity[packet[3]] == p3;
}

+static int elantech_packet_check_v2(struct psmouse *psmouse)
+{
+ struct elantech_data *etd = psmouse->private;
+ unsigned char *packet = psmouse->packet;
+
+ /*
+ * V2 hardware has two flavors. Older ones that do not report pressure,
+ * and newer ones that reports pressure and width. With newer ones, all
+ * packets (1, 2, 3 finger touch) have the same constant bits. With
+ * older ones, 1/3 finger touch packets and 2 finger touch packets
+ * have different constant bits.
+ * With all three cases, if the constant bits are not exactly what I
+ * expected, I consider them invalid.
+ */
+ 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
*/
@@ -389,14 +417,16 @@ static psmouse_ret_t elantech_process_byte(struct psmouse *psmouse)

switch (etd->hw_version) {
case 1:
- if (etd->paritycheck && !elantech_check_parity_v1(psmouse))
+ if (etd->paritycheck && !elantech_packet_check_v1(psmouse))
return PSMOUSE_BAD_DATA;

elantech_report_absolute_v1(psmouse);
break;

case 2:
- /* We don't know how to check parity in protocol v2 */
+ if (etd->paritycheck && !elantech_packet_check_v2(psmouse))
+ return PSMOUSE_BAD_DATA;
+
elantech_report_absolute_v2(psmouse);
break;
}
@@ -795,8 +825,7 @@ 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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