[PATCH 3/3] backlight: lp8864: Convert from LED to backlight class driver
From: A. Sverdlin
Date: Mon Jun 15 2026 - 08:09:26 EST
From: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxxxx>
Move the TI LP8864/LP8866 driver from drivers/leds/ to
drivers/video/backlight/ and convert it to register a backlight class
device as its primary interface.
The motivation is a use case on a hot-pluggable segment of an I2C bus.
The generic led-backlight driver (drivers/video/backlight/led_bl.c) is a
platform driver and as such inherently non-hotpluggable. It cannot react
to dynamic appearance/disappearance of the underlying I2C device. By
making the LP8864 driver directly register a backlight class device, it
becomes a native I2C driver that properly supports hot-plug/unplug
events on the I2C bus.
Key changes:
- Register a backlight class device using
devm_backlight_device_register() as the primary interface
- Implement backlight_ops (update_status, get_brightness)
- The hardware 16-bit brightness register (0x0000-0xFFFF) is directly
exposed as the backlight brightness range
- Support DT properties "default-brightness" and "max-brightness"
from the backlight common binding
- Include BL_CORE_SUSPENDRESUME for proper power management integration
- Preserve backward-compatible LED class device registration: if the
"led" child node is present in the DT, an LED class device is also
registered (same as the original driver behavior)
- Preserve the CONFIG_LEDS_LP8864 Kconfig symbol name so that existing
kernel configurations are not affected
- Update MAINTAINERS to reflect the new file location
This will be noticeable for applications which already used the LP8864
as a backend for the generic led-backlight platform driver, as a
backlight device will now appear directly in addition to the LED class
device. However, no in-tree device-trees reference this driver, so
there is no mainline impact.
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxxxx>
---
MAINTAINERS | 2 +-
drivers/leds/Kconfig | 12 --
drivers/leds/Makefile | 1 -
drivers/video/backlight/Kconfig | 15 +++
drivers/video/backlight/Makefile | 1 +
.../backlight/lp8864_bl.c} | 111 ++++++++++++++----
6 files changed, 106 insertions(+), 36 deletions(-)
rename drivers/{leds/leds-lp8864.c => video/backlight/lp8864_bl.c} (70%)
diff --git a/MAINTAINERS b/MAINTAINERS
index dbd4552236e64..250e8b1ed4bb5 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -26481,7 +26481,7 @@ M: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxxxx>
L: linux-leds@xxxxxxxxxxxxxxx
S: Maintained
F: Documentation/devicetree/bindings/leds/backlight/ti,lp8864.yaml
-F: drivers/leds/leds-lp8864.c
+F: drivers/video/backlight/lp8864_bl.c
TEXAS INSTRUMENTS' SYSTEM CONTROL INTERFACE (TISCI) PROTOCOL DRIVER
M: Nishanth Menon <nm@xxxxxx>
diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
index f4a0a3c8c8705..990cb9ef18c1e 100644
--- a/drivers/leds/Kconfig
+++ b/drivers/leds/Kconfig
@@ -529,18 +529,6 @@ config LEDS_LP8860
on the LP8860 4 channel LED driver using the I2C communication
bus.
-config LEDS_LP8864
- tristate "LED support for the TI LP8864/LP8866 4/6 channel LED drivers"
- depends on LEDS_CLASS && I2C && OF
- select REGMAP_I2C
- help
- If you say yes here you get support for the TI LP8864-Q1,
- LP8864S-Q1, LP8866-Q1, LP8866S-Q1 4/6 channel LED backlight
- drivers with I2C interface.
-
- To compile this driver as a module, choose M here: the
- module will be called leds-lp8864.
-
config LEDS_CLEVO_MAIL
tristate "Mail LED on Clevo notebook"
depends on LEDS_CLASS && BROKEN
diff --git a/drivers/leds/Makefile b/drivers/leds/Makefile
index 8fdb45d5b4393..5e624a48aa2a5 100644
--- a/drivers/leds/Makefile
+++ b/drivers/leds/Makefile
@@ -59,7 +59,6 @@ obj-$(CONFIG_LEDS_LP55XX_COMMON) += leds-lp55xx-common.o
obj-$(CONFIG_LEDS_LP8501) += leds-lp8501.o
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-$(CONFIG_LEDS_MAX5970) += leds-max5970.o
obj-$(CONFIG_LEDS_MAX77650) += leds-max77650.o
diff --git a/drivers/video/backlight/Kconfig b/drivers/video/backlight/Kconfig
index a7a3fbaf7c29e..82ecd7e46236d 100644
--- a/drivers/video/backlight/Kconfig
+++ b/drivers/video/backlight/Kconfig
@@ -514,6 +514,21 @@ config BACKLIGHT_LED
If you have a LCD backlight adjustable by LED class driver, say Y
to enable this driver.
+config LEDS_LP8864
+ tristate "Backlight driver for TI LP8864/LP8866 4/6 channel LED drivers"
+ depends on I2C && OF
+ select REGMAP_I2C
+ select NEW_LEDS
+ select LEDS_CLASS
+ help
+ If you say yes here you get support for the TI LP8864-Q1,
+ LP8864S-Q1, LP8866-Q1, LP8866S-Q1 4/6 channel LED backlight
+ drivers with I2C interface. The driver registers a backlight
+ class device and optionally an LED class device.
+
+ To compile this driver as a module, choose M here: the
+ module will be called lp8864_bl.
+
endif # BACKLIGHT_CLASS_DEVICE
endmenu
diff --git a/drivers/video/backlight/Makefile b/drivers/video/backlight/Makefile
index 794820a98ed49..6a7287d01d81b 100644
--- a/drivers/video/backlight/Makefile
+++ b/drivers/video/backlight/Makefile
@@ -62,3 +62,4 @@ obj-$(CONFIG_BACKLIGHT_WM831X) += wm831x_bl.o
obj-$(CONFIG_BACKLIGHT_ARCXCNN) += arcxcnn_bl.o
obj-$(CONFIG_BACKLIGHT_RAVE_SP) += rave-sp-backlight.o
obj-$(CONFIG_BACKLIGHT_LED) += led_bl.o
+obj-$(CONFIG_LEDS_LP8864) += lp8864_bl.o
diff --git a/drivers/leds/leds-lp8864.c b/drivers/video/backlight/lp8864_bl.c
similarity index 70%
rename from drivers/leds/leds-lp8864.c
rename to drivers/video/backlight/lp8864_bl.c
index d05211b970c94..67b28f7daedd2 100644
--- a/drivers/leds/leds-lp8864.c
+++ b/drivers/video/backlight/lp8864_bl.c
@@ -1,12 +1,13 @@
// SPDX-License-Identifier: GPL-2.0-only
/*
- * TI LP8864/LP8866 4/6 Channel LED Driver
+ * TI LP8864/LP8866 4/6 Channel LED Backlight Driver
*
- * Copyright (C) 2024 Siemens AG
+ * Copyright (C) 2024-2026 Siemens AG
*
* Based on LP8860 driver by Dan Murphy <dmurphy@xxxxxx>
*/
+#include <linux/backlight.h>
#include <linux/gpio/consumer.h>
#include <linux/i2c.h>
#include <linux/init.h>
@@ -27,6 +28,8 @@
#define LP8864_LED_STATUS 0x12
#define LP8864_LED_STATUS_WR_MASK GENMASK(14, 9) /* Writeable bits in the LED_STATUS reg */
+#define LP8864_MAX_BRIGHTNESS 0xffff
+
/* Textual meaning for status bits, starting from bit 1 */
static const char *const lp8864_supply_status_msg[] = {
"Vin under-voltage fault",
@@ -71,13 +74,15 @@ static const char *const lp8864_led_status_msg[] = {
/**
* struct lp8864
* @client: Pointer to the I2C client
- * @led_dev: led class device pointer
+ * @led_dev: optional led class device pointer
+ * @bl: backlight device pointer
* @regmap: Devices register map
* @led_status_mask: Helps to report LED fault only once
*/
struct lp8864 {
struct i2c_client *client;
- struct led_classdev led_dev;
+ struct led_classdev *led_dev;
+ struct backlight_device *bl;
struct regmap *regmap;
u16 led_status_mask;
};
@@ -157,28 +162,59 @@ static int lp8864_fault_check(struct lp8864 *priv)
return ret;
}
-static int lp8864_brightness_set(struct led_classdev *led_cdev,
- enum led_brightness brt_val)
+static int lp8864_brightness_set(struct lp8864 *priv, unsigned int brightness)
{
- struct lp8864 *priv = container_of(led_cdev, struct lp8864, led_dev);
- /* Scale 0..LED_FULL into 16-bit HW brightness */
- unsigned int val = brt_val * 0xffff / LED_FULL;
int ret;
ret = lp8864_fault_check(priv);
if (ret)
return ret;
- ret = regmap_write(priv->regmap, LP8864_BRT_CONTROL, val);
+ ret = regmap_write(priv->regmap, LP8864_BRT_CONTROL, brightness);
if (ret)
dev_err(&priv->client->dev, "Failed to write brightness value\n");
return ret;
}
-static enum led_brightness lp8864_brightness_get(struct led_classdev *led_cdev)
+static int lp8864_backlight_update_status(struct backlight_device *bl)
+{
+ return lp8864_brightness_set(bl_get_data(bl), backlight_get_brightness(bl));
+}
+
+static int lp8864_backlight_get_brightness(struct backlight_device *bl)
{
- struct lp8864 *priv = container_of(led_cdev, struct lp8864, led_dev);
+ struct lp8864 *priv = bl_get_data(bl);
+ unsigned int val;
+ int ret;
+
+ ret = regmap_read(priv->regmap, LP8864_BRT_CONTROL, &val);
+ if (ret) {
+ dev_err(&priv->client->dev, "Failed to read brightness value\n");
+ return ret;
+ }
+
+ return val;
+}
+
+static const struct backlight_ops lp8864_backlight_ops = {
+ .options = BL_CORE_SUSPENDRESUME,
+ .update_status = lp8864_backlight_update_status,
+ .get_brightness = lp8864_backlight_get_brightness,
+};
+
+static int lp8864_led_brightness_set(struct led_classdev *led_cdev,
+ enum led_brightness brt_val)
+{
+ struct lp8864 *priv = dev_get_drvdata(led_cdev->dev->parent);
+
+ /* Scale 0..LED_FULL into 16-bit HW brightness */
+ return lp8864_brightness_set(priv, brt_val * 0xffff / LED_FULL);
+}
+
+static enum led_brightness lp8864_led_brightness_get(struct led_classdev *led_cdev)
+{
+ struct lp8864 *priv = dev_get_drvdata(led_cdev->dev->parent);
unsigned int val;
int ret;
@@ -212,18 +248,15 @@ static int lp8864_probe(struct i2c_client *client)
struct device_node *np = dev_of_node(&client->dev);
struct device_node *child_node;
struct led_init_data init_data = {};
+ struct backlight_device *bl;
+ struct backlight_properties props;
struct gpio_desc *enable_gpio;
+ u32 val;
priv = devm_kzalloc(&client->dev, sizeof(*priv), GFP_KERNEL);
if (!priv)
return -ENOMEM;
- child_node = of_get_next_available_child(np, NULL);
- if (!child_node) {
- dev_err(&client->dev, "No LED function defined\n");
- return -EINVAL;
- }
-
ret = devm_regulator_get_enable_optional(&client->dev, "vled");
if (ret && ret != -ENODEV)
return dev_err_probe(&client->dev, ret, "Failed to enable vled regulator\n");
@@ -238,8 +271,7 @@ static int lp8864_probe(struct i2c_client *client)
return ret;
priv->client = client;
- priv->led_dev.brightness_set_blocking = lp8864_brightness_set;
- priv->led_dev.brightness_get = lp8864_brightness_get;
+ i2c_set_clientdata(client, priv);
priv->regmap = devm_regmap_init_i2c(client, &lp8864_regmap_config);
if (IS_ERR(priv->regmap))
@@ -258,11 +290,46 @@ static int lp8864_probe(struct i2c_client *client)
if (ret)
return ret;
+ /* Register backlight class device */
+ memset(&props, 0, sizeof(props));
+ props.type = BACKLIGHT_RAW;
+ props.max_brightness = LP8864_MAX_BRIGHTNESS;
+ props.brightness = LP8864_MAX_BRIGHTNESS;
+ props.scale = BACKLIGHT_SCALE_LINEAR;
+
+ if (!device_property_read_u32(&client->dev, "max-brightness", &val))
+ props.max_brightness = val;
+
+ if (!device_property_read_u32(&client->dev, "default-brightness", &val))
+ props.brightness = val;
+
+ bl = devm_backlight_device_register(&client->dev, "lp8864-backlight",
+ &client->dev, priv,
+ &lp8864_backlight_ops, &props);
+ if (IS_ERR(bl))
+ return dev_err_probe(&client->dev, PTR_ERR(bl),
+ "Failed to register backlight device\n");
+
+ priv->bl = bl;
+ backlight_update_status(bl);
+
+ /* Register LED class device if "led" child node is present */
+ child_node = of_get_available_child_by_name(np, "led");
+ if (!child_node)
+ return 0;
+
+ priv->led_dev = devm_kzalloc(&client->dev, sizeof(*priv->led_dev), GFP_KERNEL);
+ if (!priv->led_dev)
+ return -ENOMEM;
+
+ priv->led_dev->brightness_set_blocking = lp8864_led_brightness_set;
+ priv->led_dev->brightness_get = lp8864_led_brightness_get;
+
init_data.fwnode = of_fwnode_handle(child_node);
init_data.devicename = "lp8864";
init_data.default_label = ":display_cluster";
- ret = devm_led_classdev_register_ext(&client->dev, &priv->led_dev, &init_data);
+ ret = devm_led_classdev_register_ext(&client->dev, priv->led_dev, &init_data);
if (ret)
dev_err(&client->dev, "Failed to register LED device (%pe)\n", ERR_PTR(ret));
@@ -291,6 +358,6 @@ static struct i2c_driver lp8864_driver = {
};
module_i2c_driver(lp8864_driver);
-MODULE_DESCRIPTION("Texas Instruments LP8864/LP8866 LED driver");
+MODULE_DESCRIPTION("Texas Instruments LP8864/LP8866 LED Backlight driver");
MODULE_AUTHOR("Alexander Sverdlin <alexander.sverdlin@xxxxxxxxxxx>");
MODULE_LICENSE("GPL");
--
2.54.0