[PATCH 2/3] leds: ltc3208: add driver
From: Jan Carlo Roleda
Date: Wed Mar 18 2026 - 03:01:44 EST
Kernel driver implementation for LTC3208 Multidisplay LED Driver
Signed-off-by: Jan Carlo Roleda <jancarlo.roleda@xxxxxxxxxx>
---
MAINTAINERS | 1 +
drivers/leds/Kconfig | 11 ++
drivers/leds/Makefile | 1 +
drivers/leds/leds-ltc3208.c | 298 ++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 311 insertions(+)
diff --git a/MAINTAINERS b/MAINTAINERS
index 3f3331d7272a..48bae02057d5 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -15131,6 +15131,7 @@ M: Jan Carlo Roleda <jancarlo.roleda@xxxxxxxxxx>
L: linux-leds@xxxxxxxxxxxxxxx
S: Maintained
W: https://ez.analog.com/linux-software-drivers
+F: drivers/leds/leds-ltc3208.c
LTC4282 HARDWARE MONITOR DRIVER
M: Nuno Sa <nuno.sa@xxxxxxxxxx>
diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
index 597d7a79c988..867b120ea8ba 100644
--- a/drivers/leds/Kconfig
+++ b/drivers/leds/Kconfig
@@ -1029,6 +1029,17 @@ 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 supports the LED device LTC3208.
+
+ 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..24587942cd4e
--- /dev/null
+++ b/drivers/leds/leds-ltc3208.c
@@ -0,0 +1,298 @@
+// 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@xxxxxxxxxx>
+ */
+#include <linux/bitfield.h>
+#include <linux/errno.h>
+#include <linux/gpio/consumer.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/leds.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+#include <linux/regmap.h>
+#include <linux/types.h>
+#include <linux/workqueue.h>
+
+#define LTC3208_SET_HIGH_BYTE_DATA(x) FIELD_PREP(GENMASK(7, 4), (x))
+
+/* 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 0x5 /* AUX DAC Select */
+#define LTC3208_REG_F_CAM 0x6 /* CAM (High half-byte and Low half-byte) current DAC*/
+#define LTC3208_REG_G_OPT 0x7 /* Device Options */
+
+/* Device Options register */
+#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)
+
+/* Auxiliary DAC select masks */
+#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_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_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 *map = dev->map;
+ u8 current_level = brightness;
+
+ /*
+ * For registers with 4-bit splits (CAM, AUX/BLUE, GREEN/RED), the other
+ * half of the byte will be retrieved from the stored DAC value before
+ * updating the register.
+ */
+ switch (led->channel) {
+ case LTC3208_CHAN_MAIN:
+ return regmap_write(map, LTC3208_REG_C_MAIN, current_level);
+ case LTC3208_CHAN_SUB:
+ return regmap_write(map, LTC3208_REG_D_SUB, current_level);
+ case LTC3208_CHAN_AUX:
+ /* combine both low and high halves of byte */
+ current_level = LTC3208_SET_HIGH_BYTE_DATA(current_level);
+ current_level |= dev->leds[LTC3208_CHAN_BLUE].cdev.brightness;
+ return regmap_write(map, LTC3208_REG_B_AUXBLU, current_level);
+ case LTC3208_CHAN_BLUE:
+ /* apply high bits stored in other led */
+ current_level |= LTC3208_SET_HIGH_BYTE_DATA(
+ dev->leds[LTC3208_CHAN_AUX].cdev.brightness);
+ return regmap_write(map, LTC3208_REG_B_AUXBLU, current_level);
+ case LTC3208_CHAN_CAMH:
+ current_level = LTC3208_SET_HIGH_BYTE_DATA(current_level);
+ current_level |= dev->leds[LTC3208_CHAN_CAML].cdev.brightness;
+ return regmap_write(map, LTC3208_REG_F_CAM, current_level);
+ case LTC3208_CHAN_CAML:
+ current_level |= LTC3208_SET_HIGH_BYTE_DATA(
+ dev->leds[LTC3208_CHAN_CAMH].cdev.brightness);
+ return regmap_write(map, LTC3208_REG_F_CAM, current_level);
+ case LTC3208_CHAN_GREEN:
+ current_level = LTC3208_SET_HIGH_BYTE_DATA(current_level);
+ current_level |= dev->leds[LTC3208_CHAN_RED].cdev.brightness;
+ return regmap_write(map, LTC3208_REG_A_GRNRED, current_level);
+ case LTC3208_CHAN_RED:
+ current_level |= LTC3208_SET_HIGH_BYTE_DATA(
+ dev->leds[LTC3208_CHAN_GREEN].cdev.brightness);
+ return regmap_write(map, 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 = 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_1, enum ltc3208_aux_channel aux_2,
+ enum ltc3208_aux_channel aux_3, enum ltc3208_aux_channel aux_4)
+{
+ struct regmap *map = dev->map;
+ u8 val = FIELD_PREP(LTC3208_AUX1_MASK, aux_1) |
+ FIELD_PREP(LTC3208_AUX2_MASK, aux_2) |
+ FIELD_PREP(LTC3208_AUX3_MASK, aux_3) |
+ FIELD_PREP(LTC3208_AUX4_MASK, aux_4);
+
+ return regmap_write(map, LTC3208_REG_E_AUX, val);
+}
+
+static int ltc3208_probe(struct i2c_client *client)
+{
+ enum ltc3208_aux_channel aux_channels[LTC3208_NUM_AUX_LEDS];
+ struct ltc3208_dev *data;
+ struct ltc3208_led *leds;
+ struct regmap *map;
+ int ret, i;
+ u32 val;
+ bool dropdis_rgb_aux4;
+ bool dis_camhl;
+ bool en_rgbs;
+
+ map = devm_regmap_init_i2c(client, <c3208_regmap_cfg);
+ if (IS_ERR(map))
+ return dev_err_probe(&client->dev, PTR_ERR(map),
+ "Failed to initialize regmap\n");
+
+ data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
+ if (!data)
+ return -ENOMEM;
+
+ leds = devm_kcalloc(&client->dev, LTC3208_NUM_LED_GRPS,
+ sizeof(struct ltc3208_led), GFP_KERNEL);
+ if (!leds)
+ return -ENOMEM;
+
+ data->client = client;
+ data->map = map;
+
+ /* initialize options from devicetree */
+ 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(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 (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.\n");
+ }
+
+ ret = ltc3208_update_aux_dac(data, aux_channels[0], aux_channels[1],
+ aux_channels[2], aux_channels[3]);
+ if (ret)
+ return dev_err_probe(&client->dev, ret,
+ "error writing to aux %u channel register.\n", i);
+
+ i2c_set_clientdata(client, 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 || val >= LTC3208_NUM_LED_GRPS)
+ return dev_err_probe(&client->dev, -EINVAL,
+ "Invalid reg property for LED\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);
+ }
+
+ 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@xxxxxxxxxx>");
+MODULE_DESCRIPTION("LTC3208 LED Driver");
--
2.43.0