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    SubjectRe: [PATCH 3/6] Input: elantech - packet checking for v2 hardware
    On Thu, Aug 18, 2011 at 09:57:06AM +0800, JJ Ding wrote:
    > 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@emc.com.tw>
    > ---
    > 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;

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

    Thanks.

    --
    Dmitry


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