[PATCH v3 0/2] Add support for LTC3208 multi-display driver

[PATCH v3 0/2] Add support for LTC3208 multi-display driver

[Jan Carlo Roleda]

The LTC3208 is a multi-display LED driver, using a high-efficiency, low
noise charge pump to provide power to 5 channels (MAIN, SUB, RGB, CAM,
AUX). Current for each LED is controlled by the I2C serial interface.
Four AUX current sources can be independently assigned via the I2C port
to the CAM, SUB, MAIN, or AUX DAC controlled displays

Signed-off-by: Jan Carlo Roleda <jancarlo.roleda@analog.com>
---
Changes in v3:
- Edited device bindings descriptions
-- removed full stop in title
-- replaced quotes with double quotes for consistency
-- removed <dt-bindings/gpio/gpio.h> from example
-- removed led1-7 in example for brevity
- squashed maintainers commit to driver commit
- Link to v2: https://lore.kernel.org/r/20260326-upstream-ltc3208-v2-0-3dbc992b6098@analog.com

Changes in v2:
- Addressed DTSchema bot warnings and errors
-- removed extra blank lines
-- fixed $id to match current naming
- Addressed Kernel test warnings
-- fixed bounds for aux channel configurations
- Link to v0: https://lore.kernel.org/r/20260318-upstream-ltc3208-v1-0-015f1f1e9065@analog.com

---
Jan Carlo Roleda (2):
      leds: ltc3208: add driver
      dt-bindings: leds: Document LTC3208 Multidisplay LED Driver

 .../devicetree/bindings/leds/adi,ltc3208.yaml      | 129 +++++++++
 MAINTAINERS                                        |   8 +
 drivers/leds/Kconfig                               |  11 +
 drivers/leds/Makefile                              |   1 +
 drivers/leds/leds-ltc3208.c                        | 298 +++++++++++++++++++++
 5 files changed, 447 insertions(+)
---
base-commit: e68f95a51d1a8c1594b536c4d495cbea38d47561
change-id: 20260318-upstream-ltc3208-7cc8968bf69e

Best regards,
-- 
Jan Carlo Roleda <jancarlo.roleda@analog.com>

[PATCH v3 1/2] leds: ltc3208: add driver

[Jan Carlo Roleda]

Kernel driver implementation for LTC3208 Multidisplay LED Driver

Signed-off-by: Jan Carlo Roleda <jancarlo.roleda@analog.com>
---
 MAINTAINERS                 |   7 ++
 drivers/leds/Kconfig        |  11 ++
 drivers/leds/Makefile       |   1 +
 drivers/leds/leds-ltc3208.c | 298 ++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 317 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 55af015174a5..48bae02057d5 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -15126,6 +15126,13 @@ W:	https://ez.analog.com/linux-software-drivers
 F:	Documentation/devicetree/bindings/iio/temperature/adi,ltc2983.yaml
 F:	drivers/iio/temperature/ltc2983.c
 
+LTC3208 LED DRIVER
+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:	drivers/leds/leds-ltc3208.c
+
 LTC4282 HARDWARE MONITOR DRIVER
 M:	Nuno Sa <nuno.sa@analog.com>
 L:	linux-hwmon@vger.kernel.org
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..65e65cd73d73
--- /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@analog.com>
+ */
+#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, &ltc3208_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@analog.com>");
+MODULE_DESCRIPTION("LTC3208 LED Driver");

-- 
2.43.0

[PATCH v3 2/2] dt-bindings: leds: Document LTC3208 Multidisplay LED Driver

[Jan Carlo Roleda]

Add Documentation for LTC3208 Multidisplay LED Driver.

Signed-off-by: Jan Carlo Roleda <jancarlo.roleda@analog.com>
---
 .../devicetree/bindings/leds/adi,ltc3208.yaml      | 129 +++++++++++++++++++++
 MAINTAINERS                                        |   1 +
 2 files changed, 130 insertions(+)

diff --git a/Documentation/devicetree/bindings/leds/adi,ltc3208.yaml b/Documentation/devicetree/bindings/leds/adi,ltc3208.yaml
new file mode 100644
index 000000000000..2d53cf70e572
--- /dev/null
+++ b/Documentation/devicetree/bindings/leds/adi,ltc3208.yaml
@@ -0,0 +1,129 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+# Copyright (c) 2026 Analog Devices, Inc.
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/leds/adi,ltc3208.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: LTC3208 Multidisplay LED Controller from Linear Technologies (Now Analog Devices)
+
+maintainers:
+  - Jan Carlo Roleda <jancarlo.roleda@analog.com>
+
+description:
+  The LTC3208 is a multidisplay LED controller that can support up to 1A to all
+  connected LEDs.
+
+  The datasheet for this device can be found in
+  https://www.analog.com/en/products/ltc3208.html
+
+properties:
+  compatible:
+    const: adi,ltc3208
+
+  reg:
+    maxItems: 1
+
+  "#address-cells":
+    const: 1
+
+  "#size-cells":
+    const: 0
+
+  adi,disable-camhl-pin:
+    type: boolean
+    description:
+      Configures whether the external CAMHL pin is disabled.
+      If disabled then the output pins associated with CAM will always select
+      the CAM register's high half-byte brightness.
+
+  adi,cfg-enrgbs-pin:
+    type: boolean
+    description:
+      Configures which channel the ENRGBS pin toggles when it receives a signal.
+      ENRGBS pin controls the SUB channel's output pins if this is set,
+      or RGB channel's output pins if this is unset.
+
+  adi,disable-rgb-aux4-dropout:
+    type: boolean
+    description:
+      Configures the RGB and AUX4 dropout signals to be disabled.
+
+  adi,aux1-channel:
+    $ref: /schemas/types.yaml#/definitions/string
+    description:
+      LED Channel that the AUX1 output pin mirrors its brightness level from.
+    enum: [aux, main, sub, cam]
+    default: aux
+
+  adi,aux2-channel:
+    $ref: /schemas/types.yaml#/definitions/string
+    description:
+      LED Channel that the AUX2 output pin mirrors its brightness level from.
+    enum: [aux, main, sub, cam]
+    default: aux
+
+  adi,aux3-channel:
+    $ref: /schemas/types.yaml#/definitions/string
+    description:
+      LED Channel that the AUX3 output pin mirrors its brightness level from.
+    enum: [aux, main, sub, cam]
+    default: aux
+
+  adi,aux4-channel:
+    $ref: /schemas/types.yaml#/definitions/string
+    description:
+      LED Channel that the AUX4 output pin mirrors its brightness level from.
+    enum: [aux, main, sub, cam]
+    default: aux
+
+patternProperties:
+  "^led@[0-7]$":
+    type: object
+    $ref: /schemas/leds/common.yaml#
+    unevaluatedProperties: false
+    properties:
+      reg:
+        description:
+          LED Channel Number. each channel maps to a specific channel group used
+          to configure the brightness level of the output pins corresponding to
+          the channel.
+        enum:
+          - 0 # Main Channel (8-bit brightness)
+          - 1 # Sub Channel (8-bit brightness)
+          - 2 # AUX Channel (4-bit brightness)
+          - 3 # Camera Channel, Low-side byte (4-bit brightness)
+          - 4 # Camera Channel, High-side byte (4-bit brightness)
+          - 5 # Red Channel (4-bit brightness)
+          - 6 # Blue Channel (4-bit brightness)
+          - 7 # Green Channel (4-bit brightness)
+    required:
+      - reg
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/leds/common.h>
+    i2c {
+      #address-cells = <1>;
+      #size-cells = <0>;
+
+      led-controller@1b {
+        compatible = "adi,ltc3208";
+        reg = <0x1b>;
+        #address-cells = <1>;
+        #size-cells = <0>;
+        adi,disable-camhl-pin;
+        adi,cfg-enrgbs-pin;
+        adi,disable-rgb-aux4-dropout;
+
+        led@0 {
+          reg = <0>;
+        };
+      };
+    };
diff --git a/MAINTAINERS b/MAINTAINERS
index 48bae02057d5..97072e906928 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -15131,6 +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

-- 
2.43.0

Re: [PATCH v3 2/2] dt-bindings: leds: Document LTC3208 Multidisplay LED Driver

[Krzysztof Kozlowski]

On Mon, Apr 06, 2026 at 03:17:06PM +0800, Jan Carlo Roleda wrote:
> Add Documentation for LTC3208 Multidisplay LED Driver.
> 
> Signed-off-by: Jan Carlo Roleda <jancarlo.roleda@analog.com>
> ---

Still incorrect order.

...

> +
> +      led-controller@1b {
> +        compatible = "adi,ltc3208";
> +        reg = <0x1b>;
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +        adi,disable-camhl-pin;
> +        adi,cfg-enrgbs-pin;
> +        adi,disable-rgb-aux4-dropout;
> +
> +        led@0 {
> +          reg = <0>;

I still expect this to be complete, so at least function and color.

Best regards,
Krzysztof

Re: [PATCH v3 1/2] leds: ltc3208: add driver

[Lee Jones]

"Add driver" is not a good subject line.

> Kernel driver implementation for LTC3208 Multidisplay LED Driver

A one line commit messages is not suitable fore a 300 line driver!

What is the LTC3208 Multidisplay LED?
What does it do?
How does it operate?
What's special about it?
Any quirks?

> Signed-off-by: Jan Carlo Roleda <jancarlo.roleda@analog.com>
> ---
>  MAINTAINERS                 |   7 ++
>  drivers/leds/Kconfig        |  11 ++
>  drivers/leds/Makefile       |   1 +
>  drivers/leds/leds-ltc3208.c | 298 ++++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 317 insertions(+)
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 55af015174a5..48bae02057d5 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -15126,6 +15126,13 @@ W:	https://ez.analog.com/linux-software-drivers
>  F:	Documentation/devicetree/bindings/iio/temperature/adi,ltc2983.yaml
>  F:	drivers/iio/temperature/ltc2983.c
>  
> +LTC3208 LED DRIVER
> +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:	drivers/leds/leds-ltc3208.c
> +
>  LTC4282 HARDWARE MONITOR DRIVER
>  M:	Nuno Sa <nuno.sa@analog.com>
>  L:	linux-hwmon@vger.kernel.org
> 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.

You can do better!

> +	  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..65e65cd73d73
> --- /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@analog.com>
> + */
> +#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>

Are all of these headers strictly necessary? For instance, it doesn't appear we
are using GPIOs, platform devices, or workqueues in this driver.

> +#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)

Nit: This can look nicer nested:

#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_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

Nit: Can we have _all_ of the values line up nicely?

#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);

You can use 100-chars to avoid this awkwardness.

> +	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);

Should we be using 'regmap_update_bits()' or 'regmap_field' here instead?
Constructing the register value by reading the software state of another LED
instance could lead to races.

> +	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);

This lot is begging for a sub function:

static int ltc3208_led_set_current_level(struct regmap *regmap, u8 reg, u8 low, u8 high) {
{
	return regmap_write(regmap, reg, SET_HIGH_BYTE(high) | low);
}

> +	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);
> +

That tabbing is awkward.  In these cases it's better to do the
allocation after the declaration.

> +	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)

These should sit under the '('.

> +{
> +	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);

As above.

> +	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;

'data' is a terrible variable name.

> +	struct ltc3208_led *leds;
> +	struct regmap *map;

'regmap'

> +	int ret, i;
> +	u32 val;
> +	bool dropdis_rgb_aux4;
> +	bool dis_camhl;
> +	bool en_rgbs;
> +
> +	map = devm_regmap_init_i2c(client, &ltc3208_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 */

Capitalise comments and it's "Device Tree", although honestly, I think
the whole comment is superfluous.

> +	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");

Use 100-chars.

> +	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");

Capitalise.

> +	/* initialize aux channel configurations from devicetree */

As above and throughout.

> +	for (i = 0; i < LTC3208_NUM_AUX_LEDS; i++) {

for (int i = 0; ...

> +		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]);

Why not just aux_channels and pull the values out in the function.

> +	if (ret)
> +		return dev_err_probe(&client->dev, ret,
> +				     "error writing to aux %u channel register.\n", i);

When is 'i' not 'LTC3208_NUM_AUX_LEDS'?

> +	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");

Why aren't we propagating the real error?

> +
> +		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@analog.com>");
> +MODULE_DESCRIPTION("LTC3208 LED Driver");
> 
> -- 
> 2.43.0
> 

-- 
Lee Jones [李琼斯]