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Lukas Timmermannlag-linaro
Lukas Timmermann
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lag-linaro
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leds: as3668: Driver for the ams Osram 4-channel i2c LED driver
Since there were no existing drivers for the AS3668 or related devices, a new driver was introduced in a separate file. Similar devices were reviewed, but none shared enough characteristics to justify code reuse. As a result, this driver is written specifically for the AS3668. Signed-off-by: Lukas Timmermann <linux@timmermann.space> Link: https://patch.msgid.link/20260118165010.902086-3-linux@timmermann.space Signed-off-by: Lee Jones <lee@kernel.org>
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‎MAINTAINERS‎

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@@ -3791,6 +3791,7 @@ M: Lukas Timmermann <linux@timmermann.space>
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L: linux-leds@vger.kernel.org
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S: Maintained
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F: Documentation/devicetree/bindings/leds/ams,as3668.yaml
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F: drivers/leds/leds-as3668.c
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ASAHI KASEI AK7375 LENS VOICE COIL DRIVER
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M: Tianshu Qiu <tian.shu.qiu@intel.com>

‎drivers/leds/Kconfig‎

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Say Y to if your machine is a Dell Wyse 3020 thin client.
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config LEDS_OSRAM_AMS_AS3668
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tristate "LED support for Osram AMS AS3668"
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depends on LEDS_CLASS
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depends on I2C
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help
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This option enables support for the Osram AMS AS3668 LED controller.
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The AS3668 provides up to four LED channels and is controlled via
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the I2C bus. This driver offers basic brightness control for each
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channel, without support for blinking or other advanced features.
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To compile this driver as a module, choose M here: the module
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will be called leds-as3668.
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config LEDS_AW200XX
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tristate "LED support for Awinic AW20036/AW20054/AW20072/AW20108"
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depends on LEDS_CLASS

‎drivers/leds/Makefile‎

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@@ -15,6 +15,7 @@ obj-$(CONFIG_LEDS_ADP5520) += leds-adp5520.o
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obj-$(CONFIG_LEDS_AN30259A) += leds-an30259a.o
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obj-$(CONFIG_LEDS_APU) += leds-apu.o
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obj-$(CONFIG_LEDS_ARIEL) += leds-ariel.o
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obj-$(CONFIG_LEDS_AS3668) += leds-as3668.o
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obj-$(CONFIG_LEDS_AW200XX) += leds-aw200xx.o
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obj-$(CONFIG_LEDS_AW2013) += leds-aw2013.o
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obj-$(CONFIG_LEDS_BCM6328) += leds-bcm6328.o

‎drivers/leds/leds-as3668.c‎

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// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Osram AMS AS3668 LED Driver IC
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*
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* Copyright (C) 2025 Lukas Timmermann <linux@timmermann.space>
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*/
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#include <linux/bitfield.h>
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#include <linux/i2c.h>
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#include <linux/leds.h>
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#include <linux/module.h>
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#include <linux/uleds.h>
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#define AS3668_MAX_LEDS 4
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/* Chip Ident */
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#define AS3668_CHIP_ID1_REG 0x3e
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#define AS3668_CHIP_ID 0xa5
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/* Current Control */
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#define AS3668_CURR_MODE_REG 0x01
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#define AS3668_CURR_MODE_OFF 0x0
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#define AS3668_CURR_MODE_ON 0x1
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#define AS3668_CURR1_MODE_MASK GENMASK(1, 0)
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#define AS3668_CURR2_MODE_MASK GENMASK(3, 2)
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#define AS3668_CURR3_MODE_MASK GENMASK(5, 4)
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#define AS3668_CURR4_MODE_MASK GENMASK(7, 6)
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#define AS3668_CURR1_REG 0x02
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#define AS3668_CURR2_REG 0x03
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#define AS3668_CURR3_REG 0x04
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#define AS3668_CURR4_REG 0x05
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#define AS3668_CURR_MODE_PACK(mode) (((mode) << 0) | \
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((mode) << 2) | \
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((mode) << 4) | \
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((mode) << 6))
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struct as3668_led {
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struct led_classdev cdev;
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struct as3668 *chip;
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struct fwnode_handle *fwnode;
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u8 mode_mask;
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u8 current_reg;
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};
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struct as3668 {
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struct i2c_client *client;
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struct as3668_led leds[AS3668_MAX_LEDS];
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};
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static int as3668_channel_mode_set(struct as3668_led *led, u8 mode)
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{
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int ret;
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u8 channel_modes;
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ret = i2c_smbus_read_byte_data(led->chip->client, AS3668_CURR_MODE_REG);
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if (ret < 0) {
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dev_err(led->cdev.dev, "failed to read channel modes\n");
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return ret;
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}
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channel_modes = (u8)ret;
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channel_modes &= ~led->mode_mask;
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channel_modes |= led->mode_mask & (AS3668_CURR_MODE_PACK(mode));
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return i2c_smbus_write_byte_data(led->chip->client, AS3668_CURR_MODE_REG, channel_modes);
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}
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static enum led_brightness as3668_brightness_get(struct led_classdev *cdev)
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{
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struct as3668_led *led = container_of(cdev, struct as3668_led, cdev);
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return i2c_smbus_read_byte_data(led->chip->client, led->current_reg);
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}
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static void as3668_brightness_set(struct led_classdev *cdev, enum led_brightness brightness)
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{
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struct as3668_led *led = container_of(cdev, struct as3668_led, cdev);
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int err;
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err = as3668_channel_mode_set(led, !!brightness);
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if (err)
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dev_err(cdev->dev, "failed to set channel mode: %d\n", err);
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err = i2c_smbus_write_byte_data(led->chip->client, led->current_reg, brightness);
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if (err)
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dev_err(cdev->dev, "failed to set brightness: %d\n", err);
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}
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static int as3668_dt_init(struct as3668 *as3668)
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{
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struct device *dev = &as3668->client->dev;
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struct as3668_led *led;
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struct led_init_data init_data = {};
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int err;
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u32 reg;
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for_each_available_child_of_node_scoped(dev_of_node(dev), child) {
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err = of_property_read_u32(child, "reg", &reg);
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if (err)
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return dev_err_probe(dev, err, "failed to read 'reg' property");
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if (reg < 0 || reg >= AS3668_MAX_LEDS)
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return dev_err_probe(dev, -EINVAL,
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"unsupported LED: %d\n", reg);
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led = &as3668->leds[reg];
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led->fwnode = of_fwnode_handle(child);
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led->current_reg = reg + AS3668_CURR1_REG;
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led->mode_mask = AS3668_CURR1_MODE_MASK << (reg * 2);
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led->chip = as3668;
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led->cdev.max_brightness = U8_MAX;
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led->cdev.brightness_get = as3668_brightness_get;
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led->cdev.brightness_set = as3668_brightness_set;
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init_data.fwnode = led->fwnode;
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init_data.default_label = ":";
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err = devm_led_classdev_register_ext(dev, &led->cdev, &init_data);
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if (err)
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return dev_err_probe(dev, err, "failed to register LED %d\n", reg);
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}
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return 0;
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}
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static int as3668_probe(struct i2c_client *client)
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{
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struct as3668 *as3668;
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int err;
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u8 chip_id;
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chip_id = i2c_smbus_read_byte_data(client, AS3668_CHIP_ID1_REG);
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if (chip_id != AS3668_CHIP_ID)
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return dev_err_probe(&client->dev, -ENODEV,
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"expected chip ID 0x%02x, got 0x%02x\n",
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AS3668_CHIP_ID, chip_id);
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as3668 = devm_kzalloc(&client->dev, sizeof(*as3668), GFP_KERNEL);
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if (!as3668)
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return -ENOMEM;
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as3668->client = client;
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err = as3668_dt_init(as3668);
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if (err)
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return err;
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/* Set all four channel modes to 'off' */
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err = i2c_smbus_write_byte_data(client, AS3668_CURR_MODE_REG,
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FIELD_PREP(AS3668_CURR1_MODE_MASK, AS3668_CURR_MODE_OFF) |
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FIELD_PREP(AS3668_CURR2_MODE_MASK, AS3668_CURR_MODE_OFF) |
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FIELD_PREP(AS3668_CURR3_MODE_MASK, AS3668_CURR_MODE_OFF) |
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FIELD_PREP(AS3668_CURR4_MODE_MASK, AS3668_CURR_MODE_OFF));
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/* Set initial currents to 0mA */
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err |= i2c_smbus_write_byte_data(client, AS3668_CURR1_REG, 0);
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err |= i2c_smbus_write_byte_data(client, AS3668_CURR2_REG, 0);
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err |= i2c_smbus_write_byte_data(client, AS3668_CURR3_REG, 0);
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err |= i2c_smbus_write_byte_data(client, AS3668_CURR4_REG, 0);
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if (err)
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return dev_err_probe(&client->dev, -EIO, "failed to set zero initial current levels\n");
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return 0;
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}
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static void as3668_remove(struct i2c_client *client)
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{
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i2c_smbus_write_byte_data(client, AS3668_CURR_MODE_REG, 0);
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}
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static const struct i2c_device_id as3668_idtable[] = {
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{ "as3668" },
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{ }
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};
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MODULE_DEVICE_TABLE(i2c, as3668_idtable);
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static const struct of_device_id as3668_match_table[] = {
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{ .compatible = "ams,as3668" },
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{ }
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};
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MODULE_DEVICE_TABLE(of, as3668_match_table);
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static struct i2c_driver as3668_driver = {
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.driver = {
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.name = "leds_as3668",
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.of_match_table = as3668_match_table,
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},
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.probe = as3668_probe,
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.remove = as3668_remove,
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.id_table = as3668_idtable,
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};
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module_i2c_driver(as3668_driver);
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MODULE_AUTHOR("Lukas Timmermann <linux@timmermann.space>");
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MODULE_DESCRIPTION("AS3668 LED driver");
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MODULE_LICENSE("GPL");

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