[PATCH v4 2/2] leds: ltc3208: Add driver for LTC3208 Multidisplay LED Driver

Jan Carlo Roleda
2026-04-16T02:39:39Z

Kernel driver implementation for LTC3208 Multidisplay LED Driver.

The LTC3208 is a Multi-display LED driver, designed to control up to
7 distinct LED channels (MAIN, SUB, AUX, CAMHI, CAMLO, RED, GREEN, BLUE),
each configurable with its own current level that is equally set to its
respective output current source pins for external LEDs.

It is programmed via the I2C serial interface.
MAIN and SUB support 8-bit current level resolution,
while AUX, CAMHI/LO, RED, GREEN, and BLUE support 4-bit levels.

The AUX LED channel can be configured to mirror the CAM, SUB, and MAIN
channel current levels, or as its own independent AUX channel.

The CAM LED channel is configured as 2 separate CAMHI and CAMLO register
sub-channels, which currnet is selected via the CAMHL pin, or set to
CAMHI register only via setting the S_CAMHILO bit high in register G (0x7).

Signed-off-by: Jan Carlo Roleda <jancarlo.roleda@analog.com>
---
MAINTAINERS | 2 +-
drivers/leds/Kconfig | 12 ++
drivers/leds/Makefile | 1 +
drivers/leds/leds-ltc3208.c | 278 ++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 292 insertions(+), 1 deletion(-)

diff --git a/MAINTAINERS b/MAINTAINERS
index 19b0b84e934d..48bae02057d5 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -15131,7 +15131,7 @@ M: Jan Carlo Roleda <jancarlo.roleda@analog.com>
L: linux-leds@vger.kernel.org
S: Maintained
W: https://ez.analog.com/linux-software-drivers
-F: Documentation/devicetree/bindings/leds/adi,ltc3208.yaml
+F: drivers/leds/leds-ltc3208.c

LTC4282 HARDWARE MONITOR DRIVER
M: Nuno Sa <nuno.sa@analog.com>
diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
index 597d7a79c988..d13bbec73f06 100644
--- a/drivers/leds/Kconfig
+++ b/drivers/leds/Kconfig
@@ -1029,6 +1029,18 @@ config LEDS_ACER_A500
This option enables support for the Power Button LED of
Acer Iconia Tab A500.

+config LEDS_LTC3208
+ tristate "LED Driver for Analog Devices LTC3208"
+ depends on LEDS_CLASS && I2C
+ select REGMAP_I2C
+ help
+ Say Y to enable the LTC3208 LED driver.
+ This enables the LED device LTC3208, a 7-channel, 17-current source
+ multidisplay high-current LED driver, configured via I2C.
+
+ To compile this driver as a module, choose M here: the module will
+ be called ltc3208.
+
source "drivers/leds/blink/Kconfig"

comment "Flash and Torch LED drivers"
diff --git a/drivers/leds/Makefile b/drivers/leds/Makefile
index 8fdb45d5b439..b08b539112b6 100644
--- a/drivers/leds/Makefile
+++ b/drivers/leds/Makefile
@@ -61,6 +61,7 @@ obj-$(CONFIG_LEDS_LP8788) += leds-lp8788.o
obj-$(CONFIG_LEDS_LP8860) += leds-lp8860.o
obj-$(CONFIG_LEDS_LP8864) += leds-lp8864.o
obj-$(CONFIG_LEDS_LT3593) += leds-lt3593.o
+obj-$(CONFIG_LEDS_LTC3208) += leds-ltc3208.o
obj-$(CONFIG_LEDS_MAX5970) += leds-max5970.o
obj-$(CONFIG_LEDS_MAX77650) += leds-max77650.o
obj-$(CONFIG_LEDS_MAX77705) += leds-max77705.o
diff --git a/drivers/leds/leds-ltc3208.c b/drivers/leds/leds-ltc3208.c
new file mode 100644
index 000000000000..9da8f4b359e3
--- /dev/null
+++ b/drivers/leds/leds-ltc3208.c
@@ -0,0 +1,278 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * LED driver for Analog Devices LTC3208 Multi-Display Driver
+ *
+ * Copyright 2026 Analog Devices Inc.
+ *
+ * Author: Jan Carlo Roleda <jancarlo.roleda@analog.com>
+ */
+#include <linux/bitfield.h>
+#include <linux/errno.h>
+#include <linux/i2c.h>
+#include <linux/leds.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/property.h>
+#include <linux/regmap.h>
+#include <linux/types.h>
+
+#define LTC3208_LED_SET_HIGH_BYTE_DATA GENMASK(7, 4)
+#define LTC3208_LED_SET_LOW_BYTE_DATA GENMASK(3, 0)
+
+/* Registers */
+#define LTC3208_REG_A_GRNRED 0x1 /* Green (High half-byte) */
+ /* and Red (Low half-byte) current DAC*/
+#define LTC3208_REG_B_AUXBLU 0x2 /* AUX (High half-byte) */
+ /* and Blue (Low half-byte) current DAC*/
+#define LTC3208_REG_C_MAIN 0x3 /* Main current DAC */
+#define LTC3208_REG_D_SUB 0x4 /* Sub current DAC */
+#define LTC3208_REG_E_AUX_SELECT 0x5 /* AUX DAC Select */
+#define LTC3208_AUX1_MASK GENMASK(1, 0)
+#define LTC3208_AUX2_MASK GENMASK(3, 2)
+#define LTC3208_AUX3_MASK GENMASK(5, 4)
+#define LTC3208_AUX4_MASK GENMASK(7, 6)
+#define LTC3208_REG_F_CAM 0x6 /* CAM (High half-byte and Low half-byte) current DAC*/
+#define LTC3208_REG_G_OPT 0x7 /* Device Options */
+#define LTC3208_OPT_CPO_MASK GENMASK(7, 6)
+#define LTC3208_OPT_DIS_RGBDROP BIT(3)
+#define LTC3208_OPT_DIS_CAMHILO BIT(2)
+#define LTC3208_OPT_EN_RGBS BIT(1)
+
+#define LTC3208_MAX_BRIGHTNESS_4BIT 0xF
+#define LTC3208_MAX_BRIGHTNESS_8BIT 0xFF
+
+#define LTC3208_NUM_LED_GRPS 8
+#define LTC3208_NUM_AUX_LEDS 4
+
+#define LTC3208_NUM_AUX_OPT 4
+#define LTC3208_MAX_CPO_OPT 3
+
+enum ltc3208_aux_channel {
+ LTC3208_AUX_CHAN_AUX = 0,
+ LTC3208_AUX_CHAN_MAIN,
+ LTC3208_AUX_CHAN_SUB,
+ LTC3208_AUX_CHAN_CAM
+};
+
+enum ltc3208_channel {
+ LTC3208_CHAN_MAIN = 0,
+ LTC3208_CHAN_SUB,
+ LTC3208_CHAN_AUX,
+ LTC3208_CHAN_CAML,
+ LTC3208_CHAN_CAMH,
+ LTC3208_CHAN_RED,
+ LTC3208_CHAN_BLUE,
+ LTC3208_CHAN_GREEN
+};
+
+static const char * const ltc3208_dt_aux_channels[] = {
+ "adi,aux1-channel", "adi,aux2-channel",
+ "adi,aux3-channel", "adi,aux4-channel"
+};
+
+static const char * const ltc3208_aux_opt[] = {
+ "aux", "main", "sub", "cam"
+};
+
+struct ltc3208_led {
+ struct led_classdev cdev;
+ struct i2c_client *client;
+ enum ltc3208_channel channel;
+};
+
+struct ltc3208_dev {
+ struct i2c_client *client;
+ struct regmap *map;
+ struct ltc3208_led *leds;
+};
+
+static const struct regmap_config ltc3208_regmap_cfg = {
+ .reg_bits = 8,
+ .val_bits = 8,
+};
+
+static int ltc3208_led_set_current_low(struct regmap *regmap, u8 reg, u8 level)
+{
+ return regmap_update_bits(regmap, reg, LTC3208_LED_SET_LOW_BYTE_DATA, level);
+}
+
+static int ltc3208_led_set_current_high(struct regmap *regmap, u8 reg, u8 level)
+{
+ return regmap_update_bits(regmap, reg, LTC3208_LED_SET_HIGH_BYTE_DATA, level);
+}
+
+static int ltc3208_led_set_brightness(struct led_classdev *led_cdev, enum led_brightness brightness)
+{
+ struct ltc3208_led *led = container_of(led_cdev, struct ltc3208_led, cdev);
+ struct i2c_client *client = led->client;
+ struct ltc3208_dev *dev = i2c_get_clientdata(client);
+ struct regmap *regmap = dev->map;
+ u8 current_level = brightness;
+
+ switch (led->channel) {
+ case LTC3208_CHAN_MAIN:
+ return regmap_write(regmap, LTC3208_REG_C_MAIN, current_level);
+ case LTC3208_CHAN_SUB:
+ return regmap_write(regmap, LTC3208_REG_D_SUB, current_level);
+ case LTC3208_CHAN_AUX:
+ return ltc3208_led_set_current_high(regmap, LTC3208_REG_B_AUXBLU, current_level);
+ case LTC3208_CHAN_BLUE:
+ return ltc3208_led_set_current_low(regmap, LTC3208_REG_B_AUXBLU, current_level);
+ case LTC3208_CHAN_CAMH:
+ return ltc3208_led_set_current_high(regmap, LTC3208_REG_F_CAM, current_level);
+ case LTC3208_CHAN_CAML:
+ return ltc3208_led_set_current_low(regmap, LTC3208_REG_F_CAM, current_level);
+ case LTC3208_CHAN_GREEN:
+ return ltc3208_led_set_current_high(regmap, LTC3208_REG_A_GRNRED, current_level);
+ case LTC3208_CHAN_RED:
+ return ltc3208_led_set_current_low(regmap, LTC3208_REG_A_GRNRED, current_level);
+ default:
+ dev_err(&client->dev, "Invalid LED Channel\n");
+ return -EINVAL;
+ }
+}
+
+static int ltc3208_update_options(struct ltc3208_dev *dev,
+ bool is_sub, bool is_cam_hi, bool is_rgb_drop)
+{
+ struct regmap *map = dev->map;
+ u8 val;
+
+ val = FIELD_PREP(LTC3208_OPT_EN_RGBS, is_sub) |
+ FIELD_PREP(LTC3208_OPT_DIS_CAMHILO, is_cam_hi) |
+ FIELD_PREP(LTC3208_OPT_DIS_RGBDROP, is_rgb_drop);
+
+ return regmap_write(map, LTC3208_REG_G_OPT, val);
+}
+
+static int ltc3208_update_aux_dac(struct ltc3208_dev *dev, enum ltc3208_aux_channel *aux_chan)
+{
+ struct regmap *map = dev->map;
+ u8 val;
+
+ val = FIELD_PREP(LTC3208_AUX1_MASK, aux_chan[0]) |
+ FIELD_PREP(LTC3208_AUX2_MASK, aux_chan[1]) |
+ FIELD_PREP(LTC3208_AUX3_MASK, aux_chan[2]) |
+ FIELD_PREP(LTC3208_AUX4_MASK, aux_chan[3]);
+
+ return regmap_write(map, LTC3208_REG_E_AUX_SELECT, val);
+}
+
+static int ltc3208_probe(struct i2c_client *client)
+{
+ enum ltc3208_aux_channel aux_channels[LTC3208_NUM_AUX_LEDS];
+ struct ltc3208_dev *dev_data;
+ struct ltc3208_led *leds;
+ struct regmap *regmap;
+ int ret;
+ u32 val;
+ bool dropdis_rgb_aux4;
+ bool dis_camhl;
+ bool en_rgbs;
+
+ regmap = devm_regmap_init_i2c(client, &ltc3208_regmap_cfg);
+ if (IS_ERR(regmap))
+ return dev_err_probe(&client->dev, PTR_ERR(regmap),
+ "Failed to initialize regmap\n");
+
+ dev_data = devm_kzalloc(&client->dev, sizeof(*dev_data), GFP_KERNEL);
+ if (!dev_data)
+ return -ENOMEM;
+
+ leds = devm_kcalloc(&client->dev, LTC3208_NUM_LED_GRPS,
+ sizeof(struct ltc3208_led), GFP_KERNEL);
+ if (!leds)
+ return -ENOMEM;
+
+ dev_data->client = client;
+ dev_data->map = regmap;
+
+ dis_camhl = device_property_read_bool(&client->dev, "adi,disable-camhl-pin");
+ en_rgbs = device_property_read_bool(&client->dev, "adi,cfg-enrgbs-pin");
+ dropdis_rgb_aux4 = device_property_read_bool(&client->dev, "adi,disable-rgb-aux4-dropout");
+
+ ret = ltc3208_update_options(dev_data, en_rgbs, dis_camhl,
+ dropdis_rgb_aux4);
+ if (ret)
+ return dev_err_probe(&client->dev, ret, "error writing to options register\n");
+
+ /* Initialize aux channel configurations from devicetree */
+ for (int i = 0; i < LTC3208_NUM_AUX_LEDS; i++) {
+ ret = device_property_match_property_string(&client->dev,
+ ltc3208_dt_aux_channels[i],
+ ltc3208_aux_opt,
+ LTC3208_NUM_AUX_OPT);
+ /* Use default value if absent in devicetree */
+ if (ret == -EINVAL)
+ aux_channels[i] = LTC3208_AUX_CHAN_AUX;
+ else if (ret >= 0)
+ aux_channels[i] = ret;
+ else
+ return dev_err_probe(&client->dev, ret,
+ "Failed getting aux-channel %d\n", i);
+ }
+
+ ret = ltc3208_update_aux_dac(dev_data, aux_channels);
+ if (ret)
+ return dev_err_probe(&client->dev, ret, "error writing to aux channel register.\n");
+
+ i2c_set_clientdata(client, dev_data);
+
+ device_for_each_child_node_scoped(&client->dev, child) {
+ struct ltc3208_led *led;
+ struct led_init_data init_data = {};
+
+ ret = fwnode_property_read_u32(child, "reg", &val);
+ if (ret)
+ return dev_err_probe(&client->dev, -EINVAL,
+ "Failed to get reg value of LED.\n");
+ else if (val >= LTC3208_NUM_LED_GRPS)
+ return dev_err_probe(&client->dev, -EINVAL,
+ "LED reg value not supported.\n");
+
+ led = &leds[val];
+ led->client = client;
+ led->channel = val;
+ led->cdev.brightness_set_blocking = ltc3208_led_set_brightness;
+ led->cdev.max_brightness = LTC3208_MAX_BRIGHTNESS_4BIT;
+ if (val == LTC3208_CHAN_MAIN || val == LTC3208_CHAN_SUB)
+ led->cdev.max_brightness = LTC3208_MAX_BRIGHTNESS_8BIT;
+
+ init_data.fwnode = child;
+
+ ret = devm_led_classdev_register_ext(&client->dev, &led->cdev,
+ &init_data);
+ if (ret)
+ return dev_err_probe(&client->dev, ret, "Failed to register LED %u\n", val);
+ }
+
+ dev_data->leds = leds;
+
+ return 0;
+}
+
+static const struct of_device_id ltc3208_match_table[] = {
+ {.compatible = "adi,ltc3208"},
+ { }
+};
+MODULE_DEVICE_TABLE(of, ltc3208_match_table);
+
+static const struct i2c_device_id ltc3208_idtable[] = {
+ { "ltc3208" },
+ { }
+};
+MODULE_DEVICE_TABLE(i2c, ltc3208_idtable);
+
+static struct i2c_driver ltc3208_driver = {
+ .driver = {
+ .name = "ltc3208",
+ .of_match_table = ltc3208_match_table,
+ },
+ .id_table = ltc3208_idtable,
+ .probe = ltc3208_probe,
+};
+module_i2c_driver(ltc3208_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Jan Carlo Roleda <jancarlo.roleda@analog.com>");
+MODULE_DESCRIPTION("LTC3208 LED Driver");

--
2.43.0