From: Rudraksha Gupta <guptarud@gmail.com>

Extend the RT8515 driver to support flash ICs that use only a single
GPIO for both flash and torch modes (no separate ENT pin), with an
optional vin regulator that gates power to the flash IC.

When vin-supply is provided, the driver enables the regulator before
activating the LED and disables it when turning off.

Make ent-gpios optional and validate at probe time that exactly one of
ent-gpios or vin-supply is provided. When ent-gpios is absent, the
driver uses enf-gpios for both flash and torch brightness control.

Assisted-by: Claude:claude-opus-4.6
Signed-off-by: Rudraksha Gupta <guptarud@gmail.com>
---
 drivers/leds/flash/leds-rt8515.c | 90 ++++++++++++++++++++++++++++++++--------
 1 file changed, 72 insertions(+), 18 deletions(-)

diff --git a/drivers/leds/flash/leds-rt8515.c b/drivers/leds/flash/leds-rt8515.c
index f6b439674c03..739cac8789c8 100644
--- a/drivers/leds/flash/leds-rt8515.c
+++ b/drivers/leds/flash/leds-rt8515.c
@@ -63,16 +63,44 @@ static struct rt8515 *to_rt8515(struct led_classdev_flash *fled)
 	return container_of(fled, struct rt8515, fled);
 }
 
-static void rt8515_gpio_led_off(struct rt8515 *rt)
+static int rt8515_led_off(struct rt8515 *rt)
 {
+	int ret;
+
 	gpiod_set_value(rt->enable_flash, 0);
-	gpiod_set_value(rt->enable_torch, 0);
+	if (rt->enable_torch)
+		gpiod_set_value(rt->enable_torch, 0);
+
+	/* Disable regulator */
+	ret = regulator_is_enabled(rt->reg);
+	if (ret < 0)
+		return ret;
+	if (ret > 0)
+		return regulator_disable(rt->reg);
+
+	return 0;
 }
 
-static void rt8515_gpio_brightness_commit(struct gpio_desc *gpiod,
-					  int brightness)
+static int rt8515_set_flash_brightness(struct rt8515 *rt,
+					 struct gpio_desc *gpiod,
+					 int brightness)
 {
 	int i;
+	int ret;
+
+	/*
+	 * Reset the IC to start brightness from zero,
+	 * then re-enable and pulse to the desired level.
+	 */
+	ret = rt8515_led_off(rt);
+	if (ret)
+		return ret;
+	/* IC needs time to reset its brightness counter */
+	usleep_range(100, 200);
+	/* Enable regulator */
+	ret = regulator_enable(rt->reg);
+	if (ret)
+		return ret;
 
 	/*
 	 * Toggling a GPIO line with a small delay increases the
@@ -84,31 +112,41 @@ static void rt8515_gpio_brightness_commit(struct gpio_desc *gpiod,
 		gpiod_set_value(gpiod, 1);
 		udelay(1);
 	}
+
+	return 0;
 }
 
 /* This is setting the torch light level */
-static int rt8515_led_brightness_set(struct led_classdev *led,
+static int rt8515_set_brightness(struct led_classdev *led,
 				     enum led_brightness brightness)
 {
 	struct led_classdev_flash *fled = lcdev_to_flcdev(led);
 	struct rt8515 *rt = to_rt8515(fled);
+	int ret = 0;
 
 	mutex_lock(&rt->lock);
 
 	if (brightness == LED_OFF) {
 		/* Off */
-		rt8515_gpio_led_off(rt);
+		ret = rt8515_led_off(rt);
+		if (ret)
+			goto out;
 	} else if (brightness < RT8515_TORCH_MAX) {
-		/* Step it up to movie mode brightness using the flash pin */
-		rt8515_gpio_brightness_commit(rt->enable_torch, brightness);
+		/* Step it up to movie mode brightness */
+		ret = rt8515_set_flash_brightness(rt, rt->enable_torch ?
+				rt->enable_torch : rt->enable_flash, brightness);
+		if (ret)
+			goto out;
 	} else {
 		/* Max torch brightness requested */
-		gpiod_set_value(rt->enable_torch, 1);
+		gpiod_set_value(rt->enable_torch ? rt->enable_torch :
+				rt->enable_flash, 1);
 	}
 
+out:
 	mutex_unlock(&rt->lock);
 
-	return 0;
+	return ret;
 }
 
 static int rt8515_led_flash_strobe_set(struct led_classdev_flash *fled,
@@ -117,27 +155,33 @@ static int rt8515_led_flash_strobe_set(struct led_classdev_flash *fled,
 	struct rt8515 *rt = to_rt8515(fled);
 	struct led_flash_setting *timeout = &fled->timeout;
 	int brightness = rt->flash_max_intensity;
+	int ret = 0;
 
 	mutex_lock(&rt->lock);
 
 	if (state) {
 		/* Enable LED flash mode and set brightness */
-		rt8515_gpio_brightness_commit(rt->enable_flash, brightness);
+		ret = rt8515_set_flash_brightness(rt, rt->enable_flash, brightness);
+		if (ret)
+			goto out;
 		/* Set timeout */
 		mod_timer(&rt->powerdown_timer,
 			  jiffies + usecs_to_jiffies(timeout->val));
 	} else {
 		timer_delete_sync(&rt->powerdown_timer);
 		/* Turn the LED off */
-		rt8515_gpio_led_off(rt);
+		ret = rt8515_led_off(rt);
+		if (ret)
+			goto out;
 	}
 
 	fled->led_cdev.brightness = LED_OFF;
 	/* After this the torch LED will be disabled */
 
+out:
 	mutex_unlock(&rt->lock);
 
-	return 0;
+	return ret;
 }
 
 static int rt8515_led_flash_strobe_get(struct led_classdev_flash *fled,
@@ -166,9 +210,12 @@ static const struct led_flash_ops rt8515_flash_ops = {
 static void rt8515_powerdown_timer(struct timer_list *t)
 {
 	struct rt8515 *rt = timer_container_of(rt, t, powerdown_timer);
+	int ret;
 
 	/* Turn the LED off */
-	rt8515_gpio_led_off(rt);
+	ret = rt8515_led_off(rt);
+	if (ret)
+		dev_err(rt->dev, "failed to turn off LED (%d)\n", ret);
 }
 
 static void rt8515_init_flash_timeout(struct rt8515 *rt)
@@ -298,12 +345,18 @@ static int rt8515_probe(struct platform_device *pdev)
 		return dev_err_probe(dev, PTR_ERR(rt->enable_flash),
 				     "cannot get ENF (enable flash) GPIO\n");
 
-	/* ENT - Enable Torch line */
-	rt->enable_torch = devm_gpiod_get(dev, "ent", GPIOD_OUT_LOW);
+	/* ENT - Enable Torch line (optional for single-GPIO flash ICs) */
+	rt->enable_torch = devm_gpiod_get_optional(dev, "ent", GPIOD_OUT_LOW);
 	if (IS_ERR(rt->enable_torch))
 		return dev_err_probe(dev, PTR_ERR(rt->enable_torch),
 				     "cannot get ENT (enable torch) GPIO\n");
 
+	/* Optional VIN supply */
+	rt->reg = devm_regulator_get(dev, "vin");
+	if (IS_ERR(rt->reg))
+		return dev_err_probe(dev, PTR_ERR(rt->reg),
+				     "failed to get vin supply\n");
+
 	child = device_get_next_child_node(dev, NULL);
 	if (!child) {
 		dev_err(dev,
@@ -333,8 +386,9 @@ static int rt8515_probe(struct platform_device *pdev)
 
 	fled->ops = &rt8515_flash_ops;
 
-	led->max_brightness = rt->torch_max_intensity;
-	led->brightness_set_blocking = rt8515_led_brightness_set;
+	led->max_brightness = rt->enable_torch ?
+		rt->torch_max_intensity : rt->flash_max_intensity;
+	led->brightness_set_blocking = rt8515_set_brightness;
 	led->flags |= LED_CORE_SUSPENDRESUME | LED_DEV_CAP_FLASH;
 
 	mutex_init(&rt->lock);

-- 
2.53.0

Hi Rudraksha,

this is starting to look good, some remaining snags below:

On Thu, Mar 26, 2026 at 8:57 AM Rudraksha Gupta via B4 Relay
<devnull+guptarud.gmail.com@kernel.org> wrote:

> -static void rt8515_gpio_brightness_commit(struct gpio_desc *gpiod,
> -                                         int brightness)
> +static int rt8515_set_flash_brightness(struct rt8515 *rt,
> +                                        struct gpio_desc *gpiod,
> +                                        int brightness)

Do not change the name of the function, it's confusing.
This is also used for setting the brightness of the torch, and after
this change it looks like the function is just for the flash.

>         } else if (brightness < RT8515_TORCH_MAX) {
> -               /* Step it up to movie mode brightness using the flash pin */
> -               rt8515_gpio_brightness_commit(rt->enable_torch, brightness);
> +               /* Step it up to movie mode brightness */
> +               ret = rt8515_set_flash_brightness(rt, rt->enable_torch ?
> +                               rt->enable_torch : rt->enable_flash, brightness);
> +               if (ret)
> +                       goto out;

Add a comment befor this that if we don't have a separate torch
enable pin connected, we use the flash pin also for the torch.

Yours,
Linus Walleij