Message-ID: <49d10207-6f31-f1a1-90f1-7f8df5a83ee2@redhat.com>
Date:   Sat, 18 Mar 2023 17:43:06 +0100
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.7.1
Subject: Re: [PATCH] Input: focaltech - use explicitly signed char type
Content-Language: en-US, nl
To:     "Jason A. Donenfeld" <Jason@zx2c4.com>, dmitry.torokhov@gmail.com,
        linux-input@vger.kernel.org, linux-kernel@vger.kernel.org,
        regressions@lists.linux.dev
Cc:     stable@vger.kernel.org, regressions@leemhuis.info,
        barry@messagefor.me.uk
References: <e20db4c4-b2a8-bc88-232f-d1213733d20c@leemhuis.info>
 <20230318133010.1285202-1-Jason@zx2c4.com>
From:   Hans de Goede <hdegoede@redhat.com>
In-Reply-To: <20230318133010.1285202-1-Jason@zx2c4.com>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
Precedence: bulk

Hi,

On 3/18/23 14:30, Jason A. Donenfeld wrote:
> The recent change of -funsigned-char causes additions of negative
> numbers to become additions of large positive numbers, leading to wrong
> calculations of mouse movement. Change these casts to be explictly
> signed, to take into account negative offsets.
> 
> Fixes: 3bc753c06dd0 ("kbuild: treat char as always unsigned")
> Cc: stable@vger.kernel.org
> Cc: regressions@leemhuis.info
> Cc: barry@messagefor.me.uk
> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
> ---
> Wrote this patch from my phone, untested, so it would be nice if
> somebody with hardware could confirm it works.

Thanks, patch looks good to me:

Reviewed-by: Hans de Goede <hdegoede@redhat.com>

Regards,

Hans


> 
>  drivers/input/mouse/focaltech.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/input/mouse/focaltech.c b/drivers/input/mouse/focaltech.c
> index 6fd5fff0cbff..3dbad0d8e8c9 100644
> --- a/drivers/input/mouse/focaltech.c
> +++ b/drivers/input/mouse/focaltech.c
> @@ -202,8 +202,8 @@ static void focaltech_process_rel_packet(struct psmouse *psmouse,
>  	state->pressed = packet[0] >> 7;
>  	finger1 = ((packet[0] >> 4) & 0x7) - 1;
>  	if (finger1 < FOC_MAX_FINGERS) {
> -		state->fingers[finger1].x += (char)packet[1];
> -		state->fingers[finger1].y += (char)packet[2];
> +		state->fingers[finger1].x += (signed char)packet[1];
> +		state->fingers[finger1].y += (signed char)packet[2];
>  	} else {
>  		psmouse_err(psmouse, "First finger in rel packet invalid: %d\n",
>  			    finger1);
> @@ -218,8 +218,8 @@ static void focaltech_process_rel_packet(struct psmouse *psmouse,
>  	 */
>  	finger2 = ((packet[3] >> 4) & 0x7) - 1;
>  	if (finger2 < FOC_MAX_FINGERS) {
> -		state->fingers[finger2].x += (char)packet[4];
> -		state->fingers[finger2].y += (char)packet[5];
> +		state->fingers[finger2].x += (signed char)packet[4];
> +		state->fingers[finger2].y += (signed char)packet[5];
>  	}
>  }
>