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

[Dmitry Torokhov]

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@xxxxxxxxxx>
> ---
>  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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/