Re: [PATCH v5 2/3] leds: flash: rt8515: Support single-GPIO flash ICs with vin supply

[Lee Jones <lee@kernel.org>]

On Sun, 03 May 2026, Rudraksha Gupta via B4 Relay wrote:

> 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. When ent-gpios is absent, the driver uses
> enf-gpios for both flash and torch brightness control.
> 
> Assisted-by: Claude:claude-opus-4.6
> Reviewed-by: Linus Walleij <linusw@kernel.org>
> Signed-off-by: Rudraksha Gupta <guptarud@gmail.com>
> ---
>  drivers/leds/flash/leds-rt8515.c | 130 +++++++++++++++++++++++++++++++--------
>  1 file changed, 105 insertions(+), 25 deletions(-)
> 
> diff --git a/drivers/leds/flash/leds-rt8515.c b/drivers/leds/flash/leds-rt8515.c
> index f6b439674c03..4459874e6a6c 100644
> --- a/drivers/leds/flash/leds-rt8515.c
> +++ b/drivers/leds/flash/leds-rt8515.c
> @@ -31,6 +31,7 @@
>  #include <linux/platform_device.h>
>  #include <linux/property.h>
>  #include <linux/regulator/consumer.h>
> +#include <linux/workqueue.h>
>  
>  #include <media/v4l2-flash-led-class.h>
>  
> @@ -52,7 +53,7 @@ struct rt8515 {
>  	struct regulator *reg;
>  	struct gpio_desc *enable_torch;
>  	struct gpio_desc *enable_flash;
> -	struct timer_list powerdown_timer;
> +	struct delayed_work powerdown_work;
>  	u32 max_timeout; /* Flash max timeout */
>  	int flash_max_intensity;
>  	int torch_max_intensity;
> @@ -63,16 +64,50 @@ 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_gpio_led_off(struct rt8515 *rt)
>  {
> +	int ret;
> +
>  	gpiod_set_value(rt->enable_flash, 0);
>  	gpiod_set_value(rt->enable_torch, 0);
> +
> +	if (!rt->reg)
> +		return 0;
> +
> +	/* Disable regulator */

This comment is superfluous.

> +	ret = regulator_is_enabled(rt->reg);
> +	if (ret < 0)
> +		return ret;

Initialise ret to 0 and return ret then you can remove this branch.

> +	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_gpio_brightness_commit(struct rt8515 *rt,
> +					 struct gpio_desc *gpiod,
> +					 int brightness)

Use 100-chars to avoid this cramping.

>  {
>  	int i;
> +	int ret;
> +
> +	/*
> +	 * Reset the IC to start brightness from zero,
> +	 * then re-enable and pulse to the desired level.
> +	 */
> +	ret = rt8515_gpio_led_off(rt);
> +	if (ret)
> +		return ret;
> +
> +	/* IC needs time to reset its brightness counter */
> +	usleep_range(100, 200);
> +
> +	/* Enable regulator */

As above.

> +	if (rt->reg) {
> +		ret = regulator_enable(rt->reg);
> +		if (ret)
> +			return ret;
> +	}
>  
>  	/*
>  	 * Toggling a GPIO line with a small delay increases the
> @@ -84,6 +119,8 @@ 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 */
> @@ -92,23 +129,38 @@ static int rt8515_led_brightness_set(struct led_classdev *led,
>  {
>  	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_gpio_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.
> +		 * If there is no separate torch pin, use the flash pin
> +		 * for torch as well.
> +		 */
> +		ret = rt8515_gpio_brightness_commit(rt,
> +				rt->enable_torch ?: rt->enable_flash, brightness);
> +		if (ret)
> +			goto out;
>  	} else {
> -		/* Max torch brightness requested */
> -		gpiod_set_value(rt->enable_torch, 1);
> +		/*
> +		 * Max torch brightness requested.
> +		 * If there is no separate torch pin, use the flash pin
> +		 * for torch as well.
> +		 */
> +		gpiod_set_value(rt->enable_torch ?: rt->enable_flash, 1);

What does 1 mean in this context?  Maybe define it so it's clear.

>  	}
>  
> +out:
>  	mutex_unlock(&rt->lock);
>  
> -	return 0;
> +	return ret;
>  }
>  
>  static int rt8515_led_flash_strobe_set(struct led_classdev_flash *fled,
> @@ -117,27 +169,34 @@ 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_gpio_brightness_commit(rt, rt->enable_flash, brightness);
> +		if (ret)
> +			goto out;
> +
>  		/* Set timeout */
> -		mod_timer(&rt->powerdown_timer,
> -			  jiffies + usecs_to_jiffies(timeout->val));
> +		schedule_delayed_work(&rt->powerdown_work,
> +				      usecs_to_jiffies(timeout->val));
>  	} else {
> -		timer_delete_sync(&rt->powerdown_timer);
> +		cancel_delayed_work(&rt->powerdown_work);

Would it be safer to use 'cancel_delayed_work_sync()' here?  The previous
implementation used the synchronous 'timer_delete_sync()'.  Swapping to an
asynchronous cancellation might introduce a race condition if the work is
already executing.

>  		/* Turn the LED off */
> -		rt8515_gpio_led_off(rt);
> +		ret = rt8515_gpio_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,
> @@ -145,7 +204,7 @@ static int rt8515_led_flash_strobe_get(struct led_classdev_flash *fled,
>  {
>  	struct rt8515 *rt = to_rt8515(fled);
>  
> -	*state = timer_pending(&rt->powerdown_timer);
> +	*state = delayed_work_pending(&rt->powerdown_work);
>  
>  	return 0;
>  }
> @@ -163,12 +222,18 @@ static const struct led_flash_ops rt8515_flash_ops = {
>  	.timeout_set = rt8515_led_flash_timeout_set,
>  };
>  
> -static void rt8515_powerdown_timer(struct timer_list *t)
> +static void rt8515_powerdown_work(struct work_struct *work)
>  {
> -	struct rt8515 *rt = timer_container_of(rt, t, powerdown_timer);
> +	struct rt8515 *rt = container_of(work, struct rt8515, powerdown_work.work);
> +	int ret;
>  
>  	/* Turn the LED off */
> -	rt8515_gpio_led_off(rt);
> +	mutex_lock(&rt->lock);
> +	ret = rt8515_gpio_led_off(rt);
> +	mutex_unlock(&rt->lock);
> +
> +	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 +363,22 @@ 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");

The user doesn't care about 'ENT'.

  "Failed to obtain the Enable Torch GPIO"

> +
> +	/* Optional VIN supply */

Doesn't the function call already say this?

> +	rt->reg = devm_regulator_get_optional(dev, "vin");
> +	if (IS_ERR(rt->reg)) {
> +		ret = PTR_ERR(rt->reg);
> +		if (ret != -ENODEV)
> +			return dev_err_probe(dev, ret,
> +					     "failed to get vin supply\n");

Why are we erroring out on an optional regulator?

> +		rt->reg = NULL;
> +	}
> +
>  	child = device_get_next_child_node(dev, NULL);
>  	if (!child) {
>  		dev_err(dev,
> @@ -328,12 +403,17 @@ static int rt8515_probe(struct platform_device *pdev)
>  		dev_warn(dev,
>  			 "flash-max-timeout-us property missing\n");
>  	}
> -	timer_setup(&rt->powerdown_timer, rt8515_powerdown_timer, 0);
> +	INIT_DELAYED_WORK(&rt->powerdown_work, rt8515_powerdown_work);
>  	rt8515_init_flash_timeout(rt);
>  
>  	fled->ops = &rt8515_flash_ops;
>  
> -	led->max_brightness = rt->torch_max_intensity;
> +	/*
> +	 * If there is no separate torch pin, use the flash max intensity

Drop the "the".

> +	 * as the max brightness instead.
> +	 */
> +	led->max_brightness = rt->enable_torch ?
> +		rt->torch_max_intensity : rt->flash_max_intensity;
>  	led->brightness_set_blocking = rt8515_led_brightness_set;
>  	led->flags |= LED_CORE_SUSPENDRESUME | LED_DEV_CAP_FLASH;
>  
> @@ -372,7 +452,7 @@ static void rt8515_remove(struct platform_device *pdev)
>  	struct rt8515 *rt = platform_get_drvdata(pdev);
>  
>  	rt8515_v4l2_flash_release(rt);
> -	timer_delete_sync(&rt->powerdown_timer);
> +	cancel_delayed_work_sync(&rt->powerdown_work);
>  	mutex_destroy(&rt->lock);
>  }
>  
> 
> -- 
> 2.54.0
> 
> 

-- 
Lee Jones