linux-kernel - Re: [PATCH] Input: elantench - Fix the firmware misreport coordinates for trackpoint occasionally.

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Message-ID: <YS0+TU21/nok6Ge9@google.com>
Date:   Mon, 30 Aug 2021 13:23:41 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     phoenix <phoenix@....com.tw>
Cc:     linux-kernel@...r.kernel.org, linux-input@...r.kernel.org,
        jingle.wu@....com.tw, josh.chen@....com.tw, dave.wang@....com.tw
Subject: Re: [PATCH] Input: elantench - Fix the firmware misreport
 coordinates for trackpoint occasionally.

Hi Phoenix,

On Mon, Aug 30, 2021 at 08:19:48PM +0800, phoenix wrote:
> Hi Dmitry,
> 
> Would you review this patch, thanks
> 
> Best regards,
> Phoenix Huang
> 
> -----Original Message-----
> From: Phoenix Huang [mailto:phoenix@....com.tw] 
> Sent: Thursday, July 29, 2021 9:10 AM
> To: linux-kernel@...r.kernel.org; linux-input@...r.kernel.org;
> dmitry.torokhov@...il.com
> Cc: jingle.wu@....com.tw; josh.chen@....com.tw; dave.wang@....com.tw;
> Phoenix Huang <phoenix@....com.tw>
> Subject: [PATCH] Input: elantench - Fix the firmware misreport coordinates
> for trackpoint occasionally.
> 
> Signed-off-by: Phoenix Huang <phoenix@....com.tw>
> ---
>  drivers/input/mouse/elantech.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/drivers/input/mouse/elantech.c b/drivers/input/mouse/elantech.c
> index 2d0bc029619f..07e1098f2d31 100644
> --- a/drivers/input/mouse/elantech.c
> +++ b/drivers/input/mouse/elantech.c
> @@ -517,6 +517,17 @@ static void elantech_report_trackpoint(struct psmouse
> *psmouse,
>  	case 0x16008020U:
>  	case 0x26800010U:
>  	case 0x36808000U:
> +	
> +		/* This firmware misreport coordinates for trackpoint
> occasionally.
> +		* So we discard these packets by pattern to prevent cursor
> jumps.
> +		*/
> +		if (packet[4] == 0x80 || packet[5] == 0x80 ||
> +		    packet[1] >> 7 == packet[4] >> 7 ||

I think this will reject X coordinates in range [0, 127]. Is this really
what is needed? What kind of patterns are you observing when firmware
misreports coordinates?

Thanks.

-- 
Dmitry