Hi Dmitry,

On Thu, 18 Aug 2011 00:52:26 -0700, Dmitry Torokhov [off-list ref] wrote:

On Thu, Aug 18, 2011 at 03:31:27PM +0800, JJ Ding wrote:

quoted

Hi Dmitry,

On Wed, 17 Aug 2011 23:38:18 -0700, Dmitry Torokhov [off-list ref] wrote:

quoted

On Thu, Aug 18, 2011 at 09:57:06AM +0800, JJ Ding wrote:

quoted

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 <redacted>
---
 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;

        this is for newer v2 hardware

quoted

quoted

+
+	if ((packet[0] & 0xc0) == 0x80)
+		return (packet[0] & 0x0c) == 0x0c &&
+		       (packet[3] & 0x0e) == 0x08;

        this is for older v2, two finger touch 

quoted

quoted

+
+	return (packet[0] & 0x3c) == 0x3c &&
+	       (packet[1] & 0xf0) == 0x00 &&
+	       (packet[3] & 0x3e) == 0x38 &&
+	       (packet[4] & 0xf0) == 0x00;

        this is for older v2, 1/3 finger touch
      

quoted

Can we please spell out the assumptions under which we decide that
packet is invalid?

Thanks.

-- 
Dmitry

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.

Dmitry, how do you want me to improve this? not enough comments?

Right, if you could put the above into comments right in the
packet_simple_check_v2() that woudl be great.

Thanks.

No problem. I will do that. 

-- 
Dmitry
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