[PATCH 01/10] leds: rgb: ktd202x: Fix the flash period of short blinks on 32 bit

[Joseph Telaak via B4 Relay]

From: Joseph Telaak <joseph@xxxxxxxxxx>

When delay_on + delay_off is below 256 ms, the unsigned subtraction of
KTD202X_FLASH_PERIOD_MIN_MS wraps. On 64 bit the result truncates to -1
or -2 and gets clamped to the shortest period, but on 32 bit it
truncates to 33554431 or 33554430 and gets clamped to the longest one,
so asking for a fast blink gives a blink every 16 seconds.

Compare before subtracting.

Fixes: 0ebdb7210943 ("leds: Add ktd202x driver")
Cc: stable@xxxxxxxxxxxxxxx
Assisted-by: Claude:claude-opus-5-5
Signed-off-by: Joseph Telaak <joseph@xxxxxxxxxx>
---
 drivers/leds/rgb/leds-ktd202x.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/leds/rgb/leds-ktd202x.c b/drivers/leds/rgb/leds-ktd202x.c
index 143020945..539cf425c 100644
--- a/drivers/leds/rgb/leds-ktd202x.c
+++ b/drivers/leds/rgb/leds-ktd202x.c
@@ -296,9 +296,13 @@ static int ktd202x_blink_set(struct ktd202x_led *led, unsigned long *delay_on,
 	/* Convert into values the HW will understand. */
 
 	/* Integer representation of time of flash period */
-	num_steps = (*delay_on + *delay_off - KTD202X_FLASH_PERIOD_MIN_MS) /
-		    KTD202X_FLASH_PERIOD_STEP_MS;
-	num_steps = clamp(num_steps, 0, KTD202X_FLASH_PERIOD_MAX_STEPS);
+	delay_total_ms = *delay_on + *delay_off;
+	if (delay_total_ms < KTD202X_FLASH_PERIOD_MIN_MS)
+		num_steps = 0;
+	else
+		num_steps = min_t(unsigned long, KTD202X_FLASH_PERIOD_MAX_STEPS,
+				  (delay_total_ms - KTD202X_FLASH_PERIOD_MIN_MS) /
+				  KTD202X_FLASH_PERIOD_STEP_MS);
 
 	/* Integer representation of percentage of LED ON time */
 	on = (*delay_on * KTD202X_FLASH_ON_MAX) / (*delay_on + *delay_off);

-- 
Git-155)