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

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Date:	Thu, 18 Aug 2011 10:49:29 +0800
From:	Daniel Kurtz <djkurtz@...omium.org>
To:	JJ Ding <jj_ding@....com.tw>
Cc:	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	Seth Forshee <seth.forshee@...onical.com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Aaron Huang <aaron_huang@....com.tw>,
	Tom Lin <tom_lin@....com.tw>,
	Eric Piel <E.A.B.Piel@...elft.nl>,
	Chase Douglas <chase.douglas@...onical.com>,
	Henrik Rydberg <rydberg@...omail.se>,
	Alessandro Rubini <rubini@...l.unipv.it>
Subject: Re: [PATCH 3/6] Input: elantech - packet checking for v2 hardware

On Thu, Aug 18, 2011 at 9:57 AM, JJ Ding <jj_ding@....com.tw> 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@....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;
> +}
> +
>  /*
>  * Process byte stream from mouse and handle complete packets
>  */
> @@ -398,7 +417,9 @@ static psmouse_ret_t elantech_process_byte(struct psmouse *psmouse)
>                break;
>
>        case 2:
> -               /* We don't know how to check parity in protocol v2 */
> +               if (etd->paritycheck && !packet_simple_check_v2(psmouse))
> +                       return PSMOUSE_BAD_DATA;
> +
>                elantech_report_absolute_v2(psmouse);
>                break;
>        }
> @@ -799,8 +820,7 @@ 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 we always do some sort of check, can we just remove etd->paritycheck now?

>
>                if (etd->fw_version >= 0x020800)
>                        etd->reports_pressure = true;
> --
> 1.7.4.1
>
>
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