[PATCH v5] Input: gunze: replace deprecated APIs and fix warning style

[Bivash Kumar Singh <bivashraj750@gmail.com>]

Replace printk(KERN_WARNING) with dev_warn_ratelimited() using the
serio device, which is the correct logging style for driver code and
prevents log spam on noisy serial lines.

Replace simple_strtoul() with sscanf() to parse the comma-separated
coordinate data. NUL-terminate the receive buffer in gunze_interrupt()
before calling gunze_process_packet() so sscanf() and the warning
message can safely treat the data as a string.

Signed-off-by: Bivash Kumar Singh <bivashraj750@gmail.com>
---
Changes in v5:
  - Switch from kstrtoul() to sscanf() as suggested by Dmitry Torokhov.
    sscanf() naturally handles comma-separated coordinate data without
    needing a local buffer copy or manual NUL termination tricks.
  - NUL-terminate receive buffer in gunze_interrupt() before processing.
  - Use dev_warn_ratelimited() to prevent log spam on noisy serial lines.

Changes in v4:
  - Remove early return on kstrtoul() failure to prevent touch state
    getting permanently stuck if a release packet contains noisy data.
    Initialize x and y to 0 as safe fallback values instead.
    (reported by Sashiko AI review)

Changes in v3:
  - Fix comment style: add space after /* and use NUL instead of NULL
  - Add missing Changes section that was absent in v2

Changes in v2:
  - Copy packet data to a local NUL-terminated buffer before calling
    kstrtoul(), so the comma separator does not cause parsing to fail
    on every valid touch event. (reported by Sashiko AI review)
---
 drivers/input/touchscreen/gunze.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/drivers/input/touchscreen/gunze.c b/drivers/input/touchscreen/gunze.c
index 2baeb4f3b941..7a92052eba80 100644
--- a/drivers/input/touchscreen/gunze.c
+++ b/drivers/input/touchscreen/gunze.c
@@ -41,15 +41,20 @@ struct gunze {
 static void gunze_process_packet(struct gunze *gunze)
 {
 	struct input_dev *dev = gunze->dev;
+	unsigned int x, y;
 
-	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);
+	if (gunze->data[0] != 'T' && gunze->data[0] != 'R') {
+		dev_warn_ratelimited(&gunze->serio->dev, "bad packet: >%s<\n", 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));
+	if (sscanf(gunze->data + 1, "%4u,%4u", &x, &y) != 2) {
+		dev_warn_ratelimited(&gunze->serio->dev, "bad packet: >%s<\n", gunze->data);
+		return;
+	}
+
+	input_report_abs(dev, ABS_X, x);
+	input_report_abs(dev, ABS_Y, 1024 - y);
 	input_report_key(dev, BTN_TOUCH, gunze->data[0] == 'T');
 	input_sync(dev);
 }
@@ -60,6 +65,7 @@ static irqreturn_t gunze_interrupt(struct serio *serio,
 	struct gunze *gunze = serio_get_drvdata(serio);
 
 	if (data == '\r') {
+		gunze->data[gunze->idx] = '\0';
 		gunze_process_packet(gunze);
 		gunze->idx = 0;
 	} else {
-- 
2.53.0