Re: [PATCH v4] Input: gunze: replace deprecated APIs and fix warning style

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 3 potential issue(s) to consider:

New issues:
- [High] Un-ratelimited dev_warn() calls in the interrupt handler lead to severe kernel log spam (dmesg flooding).
- [High] Replacing simple_strtoul() with kstrtoul() causes a behavioral regression due to strict parsing requirements.

Pre-existing issues:
- [High] Unconditional reporting of fallback coordinates on parse failure causes out-of-bounds values and cursor jumps.
--

--- Patch [1]: [PATCH v4] Input: gunze: replace deprecated APIs and fix warning style ---
commit 7f14b2c0978a817cc80d8103302866bba7c3bf3f
Author: Bivash Kumar Singh <bivashraj750@gmail.com>

Input: gunze: replace deprecated APIs and fix warning style

This commit replaces simple_strtoul() with kstrtoul() by copying the packet
data into a local NUL-terminated buffer first. It also updates the logging
style from printk() to dev_warn().

> diff --git a/drivers/input/touchscreen/gunze.c b/drivers/input/touchscreen/gunze.c
> --- a/drivers/input/touchscreen/gunze.c
> +++ b/drivers/input/touchscreen/gunze.c
> @@ -41,15 +41,26 @@ static void gunze_process_packet(struct gunze *gunze)
>  	struct input_dev *dev = gunze->dev;
> +	char buf[GUNZE_MAX_LENGTH + 1];
> +	unsigned long x = 0, y = 0;
>  
>  	if (gunze->idx != GUNZE_MAX_LENGTH || gunze->data[5] != ',' ||
>  		(gunze->data[0] != 'T' && gunze->data[0] != 'R')) {
> -		printk(KERN_WARNING "gunze.c: bad packet: >%.*s<\n", GUNZE_MAX_LENGTH, gunze->data);
> +		dev_warn(&gunze->serio->dev, "bad packet: >%.*s<\n", GUNZE_MAX_LENGTH, gunze->data);
>  		return;
>  	}
>  
> -	input_report_abs(dev, ABS_X, simple_strtoul(gunze->data + 1, NULL, 10));
> -	input_report_abs(dev, ABS_Y, 1024 - simple_strtoul(gunze->data + 6, NULL, 10));
> +	memcpy(buf, gunze->data, GUNZE_MAX_LENGTH);
> +	buf[5] = '\0';		/* NUL-terminate X portion: "1234\0" */
> +	buf[GUNZE_MAX_LENGTH] = '\0';	/* NUL-terminate Y portion */
> +
> +	if (kstrtoul(buf + 1, 10, &x))

[Severity: High]
In gunze_process_packet(), kstrtoul() requires a perfectly clean string
without trailing spaces or non-digit characters, whereas simple_strtoul()
would successfully stop parsing at the first non-digit.

If the legacy fixed-width hardware protocol pads coordinates with spaces
or contains noisy data, will kstrtoul() reject the entire packet and
return -EINVAL, resulting in a loss of valid touch coordinate data?

> +		dev_warn(&gunze->serio->dev, "failed to parse X coordinate\n");
> +	if (kstrtoul(buf + 6, 10, &y))
> +		dev_warn(&gunze->serio->dev, "failed to parse Y coordinate\n");

[Severity: High]
The commit message mentions that release packets can contain noisy data,
meaning parsing failures are an expected event.

Because gunze_process_packet() is called directly from the hardware interrupt
handler, could these un-ratelimited dev_warn() calls flood the kernel log and
cause high CPU overhead when users interact with the touchscreen?

> +
> +	input_report_abs(dev, ABS_X, x);
> +	input_report_abs(dev, ABS_Y, 1024 - y);

[Severity: High]
This is a pre-existing issue, but when parsing fails, the y coordinate falls
back to 0.

Does unconditionally reporting ABS_Y as 1024 - 0 cause the touch cursor to
instantaneously jump out of bounds and trigger spurious clicks or swipe
artifacts on the device?

>  	input_report_key(dev, BTN_TOUCH, gunze->data[0] == 'T');
>  	input_sync(dev);
>  }

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260719173700.4942-1-bivashraj750@gmail.com?part=1