Re: [PATCH v5 07/11] leds: flash: add support for Samsung S2M series PMIC flash LED device

["Kaustabh Chakraborty" <kauschluss@disroot.org>]

On 2026-05-07 17:46 +01:00, Lee Jones wrote:
> On Fri, 24 Apr 2026, Kaustabh Chakraborty wrote:
>
>> Add support for flash LEDs in certain Samsung S2M series PMICs.
>> The device has two channels for LEDs, typically for the back and front
>> cameras in mobile devices. Both channels can be independently
>> controlled, and can be operated in torch or flash modes.
>> 
>> The driver includes initial support for the S2MU005 PMIC flash LEDs.
>> 
>> Signed-off-by: Kaustabh Chakraborty <kauschluss@disroot.org>
>> ---
>>  drivers/leds/flash/Kconfig          |  12 ++
>>  drivers/leds/flash/Makefile         |   1 +
>>  drivers/leds/flash/leds-s2m-flash.c | 358 ++++++++++++++++++++++++++++++++++++
>>  3 files changed, 371 insertions(+)
>> 
>> diff --git a/drivers/leds/flash/Kconfig b/drivers/leds/flash/Kconfig
>> index 5e08102a67841..be62e05277429 100644
>> --- a/drivers/leds/flash/Kconfig
>> +++ b/drivers/leds/flash/Kconfig
>> @@ -114,6 +114,18 @@ config LEDS_RT8515
>>  	  To compile this driver as a module, choose M here: the module
>>  	  will be called leds-rt8515.
>>  
>> +config LEDS_S2M_FLASH
>> +	tristate "Samsung S2M series PMICs flash/torch LED support"
>> +	depends on LEDS_CLASS
>> +	depends on MFD_SEC_CORE
>> +	depends on V4L2_FLASH_LED_CLASS || !V4L2_FLASH_LED_CLASS
>
> The `|| !V4L2_FLASH_LED_CLASS` part of this dependency makes it
> unconditionally true. Was this intended? Perhaps this dependency can be
> removed entirely.

Right? Similar lines are also present in entries of other drivers too.
It is indeed weird, but I disregarded my doubts and added it anyway.

>> +	select REGMAP_IRQ
>> +	help
>> +	  This option enables support for the flash/torch LEDs found in
>> +	  certain Samsung S2M series PMICs, such as the S2MU005. It has
>> +	  a LED channel dedicated for every physical LED. The LEDs can
>> +	  be controlled in flash and torch modes.
>> +
>>  config LEDS_SGM3140
>>  	tristate "LED support for the SGM3140"
>>  	depends on V4L2_FLASH_LED_CLASS || !V4L2_FLASH_LED_CLASS
>> diff --git a/drivers/leds/flash/Makefile b/drivers/leds/flash/Makefile
>> index 712fb737a428e..44e6c1b4beb37 100644
>> --- a/drivers/leds/flash/Makefile
>> +++ b/drivers/leds/flash/Makefile
>> @@ -10,6 +10,7 @@ obj-$(CONFIG_LEDS_MAX77693)	+= leds-max77693.o
>>  obj-$(CONFIG_LEDS_QCOM_FLASH)	+= leds-qcom-flash.o
>>  obj-$(CONFIG_LEDS_RT4505)	+= leds-rt4505.o
>>  obj-$(CONFIG_LEDS_RT8515)	+= leds-rt8515.o
>> +obj-$(CONFIG_LEDS_S2M_FLASH)	+= leds-s2m-flash.o
>>  obj-$(CONFIG_LEDS_SGM3140)	+= leds-sgm3140.o
>>  obj-$(CONFIG_LEDS_SY7802)	+= leds-sy7802.o
>>  obj-$(CONFIG_LEDS_TPS6131X)	+= leds-tps6131x.o
>> diff --git a/drivers/leds/flash/leds-s2m-flash.c b/drivers/leds/flash/leds-s2m-flash.c
>> new file mode 100644
>> index 0000000000000..177d23b432ce6
>> --- /dev/null
>> +++ b/drivers/leds/flash/leds-s2m-flash.c
>> @@ -0,0 +1,358 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Flash and Torch LED Driver for Samsung S2M series PMICs.
>> + *
>> + * Copyright (c) 2015 Samsung Electronics Co., Ltd
>> + * Copyright (c) 2026 Kaustabh Chakraborty <kauschluss@disroot.org>
>> + */
>> +
>> +#include <linux/container_of.h>
>> +#include <linux/led-class-flash.h>
>> +#include <linux/mfd/samsung/core.h>
>> +#include <linux/mfd/samsung/s2mu005.h>
>> +#include <linux/module.h>
>> +#include <linux/of.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/regmap.h>
>> +#include <media/v4l2-flash-led-class.h>
>> +
>> +#define MAX_CHANNELS	2
>> +
>> +struct s2m_led {
>> +	struct regmap *regmap;
>> +	struct led_classdev_flash fled;
>> +	struct v4l2_flash *v4l2_flash;
>> +	/*
>> +	 * The mutex object prevents the concurrent access of flash control
>> +	 * registers by the LED and V4L2 subsystems.
>> +	 */
>> +	struct mutex lock;
>> +	unsigned int reg_enable;
>> +	u8 channel;
>> +	u8 flash_brightness;
>> +	u8 flash_timeout;
>> +};
>> +
>> +static struct s2m_led *to_s2m_led(struct led_classdev_flash *fled)
>> +{
>> +	return container_of(fled, struct s2m_led, fled);
>> +}
>> +
>> +static struct led_classdev_flash *to_s2m_fled(struct led_classdev *cdev)
>> +{
>> +	return container_of(cdev, struct led_classdev_flash, led_cdev);
>> +}
>> +
>> +static int s2m_fled_flash_brightness_set(struct led_classdev_flash *fled, u32 brightness)
>> +{
>> +	struct s2m_led *led = to_s2m_led(fled);
>> +	struct led_flash_setting *setting = &fled->brightness;
>> +
>> +	led->flash_brightness = (brightness - setting->min) / setting->step;
>> +
>> +	return 0;
>> +}
>> +
>> +static int s2m_fled_flash_timeout_set(struct led_classdev_flash *fled, u32 timeout)
>> +{
>> +	struct s2m_led *led = to_s2m_led(fled);
>> +	struct led_flash_setting *setting = &fled->timeout;
>> +
>> +	led->flash_timeout = (timeout - setting->min) / setting->step;
>> +
>> +	return 0;
>> +}
>> +
>> +#if IS_ENABLED(CONFIG_V4L2_FLASH_LED_CLASS)
>> +static int s2m_fled_flash_external_strobe_set(struct v4l2_flash *v4l2_flash, bool enable)
>> +{
>> +	struct s2m_led *led = to_led(v4l2_flash->fled_cdev);
>
> What is to_led()?
>
> Was this tested?

I honestly don't know what happened here, and yes this (well, not this
precisely) was tested. I had changed something later? Don't know, its
odd. Will fix.

>> +	mutex_lock(&led->lock);
>> +
>> +	led->fled.ops->strobe_set(&led->fled, enable);
>> +
>> +	mutex_unlock(&led->lock);
>> +
>> +	return 0;
>> +}
>> +
>> +static const struct v4l2_flash_ops s2m_fled_v4l2_flash_ops = {
>> +	.external_strobe_set = s2m_fled_flash_external_strobe_set,
>> +};
>> +#else
>> +static const struct v4l2_flash_ops s2m_fled_v4l2_flash_ops;
>> +#endif
>> +
>> +static void s2m_fled_v4l2_flash_release(void *v4l2_flash)
>> +{
>> +	v4l2_flash_release(v4l2_flash);
>> +}
>> +
>> +static int s2mu005_fled_torch_brightness_set(struct led_classdev *cdev, enum led_brightness value)
>> +{
>> +	struct s2m_led *led = to_s2m_led(to_s2m_fled(cdev));
>> +	int ret;
>> +
>> +	mutex_lock(&led->lock);
>> +
>> +	if (!value) {
>> +		ret = regmap_clear_bits(led->regmap, led->reg_enable,
>> +					S2MU005_FLED_TORCH_EN(led->channel));
>> +		if (ret < 0)
>> +			dev_err(cdev->dev, "failed to disable torch LED\n");
>> +		goto unlock;
>> +	}
>> +
>> +	ret = regmap_update_bits(led->regmap, S2MU005_REG_FLED_CH_CTRL1(led->channel),
>> +				 S2MU005_FLED_TORCH_IOUT,
>> +				 FIELD_PREP(S2MU005_FLED_TORCH_IOUT, value - 1));
>> +	if (ret < 0) {
>
> Is a positive number even possible?

As per the docs, no. Will fix here and in other instances as well.

>> +		dev_err(cdev->dev, "failed to set torch current\n");
>> +		goto unlock;
>> +	}
>> +
>> +	ret = regmap_set_bits(led->regmap, led->reg_enable, S2MU005_FLED_TORCH_EN(led->channel));
>> +	if (ret < 0) {
>> +		dev_err(cdev->dev, "failed to enable torch LED\n");
>> +		goto unlock;
>> +	}
>> +
>> +unlock:
>> +	mutex_unlock(&led->lock);
>> +
>> +	return ret;
>> +}
>> +
>> +static int s2mu005_fled_flash_strobe_set(struct led_classdev_flash *fled, bool state)
>> +{
>> +	struct s2m_led *led = to_s2m_led(fled);
>> +	int ret;
>> +
>> +	mutex_lock(&led->lock);
>> +
>> +	ret = regmap_clear_bits(led->regmap, led->reg_enable, S2MU005_FLED_FLASH_EN(led->channel));
>> +	if (ret < 0) {
>> +		dev_err(fled->led_cdev.dev, "failed to disable flash LED\n");
>> +		goto unlock;
>> +	}
>> +
>> +	if (!state)
>> +		goto unlock;
>> +
>> +	ret = regmap_update_bits(led->regmap, S2MU005_REG_FLED_CH_CTRL0(led->channel),
>> +				 S2MU005_FLED_FLASH_IOUT,
>> +				 FIELD_PREP(S2MU005_FLED_FLASH_IOUT, led->flash_brightness));
>> +	if (ret < 0) {
>> +		dev_err(fled->led_cdev.dev, "failed to set flash brightness\n");
>> +		goto unlock;
>> +	}
>> +
>> +	ret = regmap_update_bits(led->regmap, S2MU005_REG_FLED_CH_CTRL3(led->channel),
>> +				 S2MU005_FLED_FLASH_TIMEOUT,
>> +				 FIELD_PREP(S2MU005_FLED_FLASH_TIMEOUT, led->flash_timeout));
>> +	if (ret < 0) {
>> +		dev_err(fled->led_cdev.dev, "failed to set flash timeout\n");
>> +		goto unlock;
>> +	}
>> +
>> +	ret = regmap_set_bits(led->regmap, led->reg_enable, S2MU005_FLED_FLASH_EN(led->channel));
>> +	if (ret < 0) {
>> +		dev_err(fled->led_cdev.dev, "failed to enable flash LED\n");
>> +		goto unlock;
>> +	}
>> +
>> +unlock:
>> +	mutex_unlock(&led->lock);
>> +
>> +	return 0;
>
> It seems like this function swallows error codes.
>
> Better if they're propagated properly.
>
>> +}
>> +
>> +static int s2mu005_fled_flash_strobe_get(struct led_classdev_flash *fled, bool *state)
>> +{
>> +	struct s2m_led *led = to_s2m_led(fled);
>> +	u32 val;
>> +	int ret;
>> +
>> +	mutex_lock(&led->lock);
>> +
>> +	ret = regmap_read(led->regmap, S2MU005_REG_FLED_STATUS, &val);
>> +	if (ret < 0) {
>> +		dev_err(fled->led_cdev.dev, "failed to fetch LED status");
>
> Missed '/n'.
>
>> +		goto unlock;
>> +	}
>> +
>> +	*state = !!(val & S2MU005_FLED_FLASH_STATUS(led->channel));
>> +
>> +unlock:
>> +	mutex_unlock(&led->lock);
>> +
>> +	return ret;
>> +}
>> +
>> +static const struct led_flash_ops s2mu005_fled_flash_ops = {
>> +	.flash_brightness_set = s2m_fled_flash_brightness_set,
>> +	.timeout_set = s2m_fled_flash_timeout_set,
>> +	.strobe_set = s2mu005_fled_flash_strobe_set,
>> +	.strobe_get = s2mu005_fled_flash_strobe_get,
>> +};
>> +
>> +static int s2mu005_fled_init(struct s2m_led *led, struct device *dev, struct regmap *regmap,
>> +			     unsigned int nr_channels)
>> +{
>> +	unsigned int val;
>> +	int i, ret;
>> +
>> +	/* Enable the LED channels. */
>> +	ret = regmap_set_bits(regmap, S2MU005_REG_FLED_CTRL1, S2MU005_FLED_CH_EN);
>> +	if (ret < 0)
>> +		return dev_err_probe(dev, ret, "failed to enable LED channels\n");
>> +
>> +	ret = regmap_read(regmap, S2MU005_REG_ID, &val);
>> +	if (ret < 0)
>> +		return dev_err_probe(dev, ret, "failed to read revision\n");
>> +
>> +	for (i = 0; i < nr_channels; i++) {
>
> for (int i = 0; i < nr_channels; i++)

Is that allowed in the kernel source? I have never seen variable
declaration in a for loop.

>> +		/*
>> +		 * Read the revision register. Revision EVT0 has the register
>> +		 * at CTRL4, while EVT1 and higher have it at CTRL6.
>> +		 */
>> +		if (FIELD_GET(S2MU005_ID_MASK, val) == 0)
>
> Why not remove the " == 0" and reverse the branches?

My intention was to make it explicit that the value used is an integer
value, as opposed to a boolean.

>> +			led[i].reg_enable = S2MU005_REG_FLED_CTRL4;
>> +		else
>> +			led[i].reg_enable = S2MU005_REG_FLED_CTRL6;
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>> +static int s2mu005_fled_init_channel(struct s2m_led *led, struct device *dev,
>> +				     struct fwnode_handle *fwnp)
>> +{
>> +	struct led_classdev *cdev = &led->fled.led_cdev;
>> +	struct led_init_data init_data = {};
>> +	struct v4l2_flash_config v4l2_cfg = {};
>> +	int ret;
>> +
>> +	cdev->max_brightness = 16;
>> +	cdev->brightness_set_blocking = s2mu005_fled_torch_brightness_set;
>> +	cdev->flags |= LED_DEV_CAP_FLASH;
>> +
>> +	led->fled.timeout.min = 62000;
>> +	led->fled.timeout.step = 62000;
>> +	led->fled.timeout.max = 992000;
>> +	led->fled.timeout.val = 992000;
>> +
>> +	led->fled.brightness.min = 25000;
>> +	led->fled.brightness.step = 25000;
>> +	led->fled.brightness.max = 375000; /* 400000 causes flickering */
>> +	led->fled.brightness.val = 375000;
>> +
>> +	s2m_fled_flash_timeout_set(&led->fled, led->fled.timeout.val);
>> +	s2m_fled_flash_brightness_set(&led->fled, led->fled.brightness.val);
>> +
>> +	led->fled.ops = &s2mu005_fled_flash_ops;
>> +
>> +	init_data.fwnode = fwnp;
>> +	ret = devm_led_classdev_flash_register_ext(dev, &led->fled, &init_data);
>> +	if (ret < 0)
>> +		return dev_err_probe(dev, ret, "failed to create LED flash device\n");
>> +
>> +	v4l2_cfg.intensity.min = led->fled.timeout.min;
>> +	v4l2_cfg.intensity.step = led->fled.timeout.step;
>> +	v4l2_cfg.intensity.max = led->fled.timeout.max;
>> +	v4l2_cfg.intensity.val = led->fled.timeout.val;
>
> Is it correct to configure the V4L2 intensity settings from the timeout
> values?  I would expect these to be based on the brightness settings.

Stupid me. Admittedly, I am unable to test the v4l2 functionality
properly for now. I will remove all related code in the next revision.
Will add them back when they're needed and I'm able to test.

>> +
>> +	v4l2_cfg.has_external_strobe = true;
>> +
>> +	led->v4l2_flash = v4l2_flash_init(dev, fwnp, &led->fled, &s2m_fled_v4l2_flash_ops,
>> +					  &v4l2_cfg);
>> +	if (IS_ERR(led->v4l2_flash)) {
>> +		v4l2_flash_release(led->v4l2_flash);
>
> So you're going to try and release an error?
>
>> +		return dev_err_probe(dev, PTR_ERR(led->v4l2_flash),
>> +				     "failed to create V4L2 flash device\n");
>> +	}
>> +
>> +	ret = devm_add_action_or_reset(dev, (void *)s2m_fled_v4l2_flash_release, led->v4l2_flash);
>> +	if (ret < 0)
>> +		return dev_err_probe(dev, ret, "failed to add cleanup action\n");
>> +
>> +	return 0;
>> +}
>> +
>> +static int s2m_fled_probe(struct platform_device *pdev)
>> +{
>> +	struct device *dev = &pdev->dev;
>> +	struct sec_pmic_dev *ddata = dev_get_drvdata(dev->parent);
>> +	struct s2m_led *led;
>> +	int ret;
>> +
>> +	led = devm_kzalloc(dev, sizeof(*led) * MAX_CHANNELS, GFP_KERNEL);
>> +	if (!led)
>> +		return -ENOMEM;
>> +
>> +	switch (platform_get_device_id(pdev)->driver_data) {
>> +	case S2MU005:
>> +		ret = s2mu005_fled_init(led, dev, ddata->regmap_pmic, MAX_CHANNELS);
>> +		if (ret)
>> +			return ret;
>> +		break;
>> +	default:
>> +		return dev_err_probe(dev, -ENODEV, "device type %d is not supported by driver\n",
>> +				     ddata->device_type);
>> +	}
>
> Will this be expanded in the very near future?
>
> If not, having a switch () with only one entry seems odd.

I have plans to introduce support for S2MU004 at one point. I'll change
it now, and re-introduce the switch block later.

> if (platform_get_device_id(pdev)->driver_data != S2MU005)
> 	dev_err_probe()
>
>> +	device_for_each_child_node_scoped(dev, child) {
>> +		u32 reg;
>> +
>> +		if (fwnode_property_read_u32(child, "reg", &reg))
>> +			continue;
>> +
>> +		if (led[reg].regmap) {
>> +			dev_warn(dev, "duplicate node for channel %d\n", reg);
>> +			continue;
>> +		}
>
> If reg > MAX_CHANNELS, you just created an OOB condition.
>
>> +
>> +		led[reg].regmap = ddata->regmap_pmic;
>> +		led[reg].channel = (u8)reg;
>> +
>> +		ret = devm_mutex_init(dev, &led[reg].lock);
>> +		if (ret)
>> +			return dev_err_probe(dev, ret, "failed to create mutex\n");
>> +
>> +		switch (platform_get_device_id(pdev)->driver_data) {
>> +		case S2MU005:
>> +			ret = s2mu005_fled_init_channel(led + reg, dev, child);
>> +			if (ret < 0)
>> +				return ret;
>> +			break;
>> +		}
>
> This is even more odd!

What's exactly odd about it?

>> +	}
>> +
>> +	return 0;
>> +}
>> +
>> +static const struct platform_device_id s2m_fled_id_table[] = {
>> +	{ "s2mu005-flash", S2MU005 },
>> +	{ /* sentinel */ },
>> +};
>> +MODULE_DEVICE_TABLE(platform, s2m_fled_id_table);
>> +
>> +static const struct of_device_id s2m_fled_of_match_table[] = {
>> +	{ .compatible = "samsung,s2mu005-flash", .data = (void *)S2MU005 },
>> +	{ /* sentinel */ },
>> +};
>> +MODULE_DEVICE_TABLE(of, s2m_fled_of_match_table);
>> +
>> +static struct platform_driver s2m_fled_driver = {
>> +	.driver = {
>> +		.name = "s2m-flash",
>> +	},
>> +	.probe = s2m_fled_probe,
>> +	.id_table = s2m_fled_id_table,
>> +};
>> +module_platform_driver(s2m_fled_driver);
>> +
>> +MODULE_DESCRIPTION("Flash/Torch LED Driver For Samsung S2M Series PMICs");
>> +MODULE_AUTHOR("Kaustabh Chakraborty <kauschluss@disroot.org>");
>> +MODULE_LICENSE("GPL");