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

Dmitry Torokhov
2011-08-18T06:38:25Z

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