# Re: \[PATCH 2/2\] backlight: add ktd3137 support - From: Daniel Thompson \ - Date: 2026-11-03 14:15:51 - List: linux-fbdev - Page: https://ratatoskr.run/linux-fbdev/2026/11/17853233 - Thread: https://ratatoskr.run/dri-devel/2026/11/17847320/t.md ```text On Mon, Nov 02, 2026 at 09:58:49PM +0200, Roman Vivchar via B4 Relay wrote: > From: Roman Vivchar > > Add support for the KTD3137 display backlight IC. It's used in various > Xiaomi phones, such as Xiaomi Redmi Note 9. > > Signed-off-by: Roman Vivchar > --- > MAINTAINERS | 1 + > drivers/video/backlight/Kconfig | 11 ++ > drivers/video/backlight/Makefile | 1 + > drivers/video/backlight/ktd3137.c | 262 ++++++++++++++++++++++++++++++++++++++ > 4 files changed, 275 insertions(+) > > diff --git a/MAINTAINERS b/MAINTAINERS > index 24dd5b43f167..23114fd09445 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -14622,6 +14622,7 @@ KTD3137 BACKLIGHT DRIVER > M: Roman Vivchar [ref] > S: Maintained > F: Documentation/devicetree/bindings/leds/backlight/kinetic,ktd3137.yaml > +F: drivers/video/backlight/ktd3137.c > > KTEST > M: Steven Rostedt [ref] > diff --git a/drivers/video/backlight/Kconfig b/drivers/video/backlight/Kconfig > index 7c66b8840d88..0196b8597367 100644 > --- a/drivers/video/backlight/Kconfig > +++ b/drivers/video/backlight/Kconfig > @@ -199,6 +199,17 @@ config BACKLIGHT_KTD2801 > Say Y to enable the backlight driver for the Kinetic KTD2801 1-wire > GPIO-controlled backlight found in Samsung Galaxy Core Prime VE LTE. > > +config BACKLIGHT_KTD3137 > + tristate "Backlight Driver for Kinetic KTD3137" > + depends on I2C > + select REGMAP_I2C > + help > + Say Y to enable the backlight driver for the Kinetic KTD3137 > + found in various Xiaomi smartphones. > + > + To compile this driver as a module, choose M here: the module > + will be called ktd3137. > + > config BACKLIGHT_KTZ8866 > tristate "Backlight Driver for Kinetic KTZ8866" > depends on I2C > diff --git a/drivers/video/backlight/Makefile b/drivers/video/backlight/Makefile > index 34469711c6cd..b2d3b69e9e32 100644 > --- a/drivers/video/backlight/Makefile > +++ b/drivers/video/backlight/Makefile > @@ -38,6 +38,7 @@ obj-$(CONFIG_BACKLIGHT_HP700) += jornada720_bl.o > obj-$(CONFIG_BACKLIGHT_IPAQ_MICRO) += ipaq_micro_bl.o > obj-$(CONFIG_BACKLIGHT_KTD253) += ktd253-backlight.o > obj-$(CONFIG_BACKLIGHT_KTD2801) += ktd2801-backlight.o > +obj-$(CONFIG_BACKLIGHT_KTD3137) += ktd3137.o > obj-$(CONFIG_BACKLIGHT_KTZ8866) += ktz8866.o > obj-$(CONFIG_BACKLIGHT_LM3509) += lm3509_bl.o > obj-$(CONFIG_BACKLIGHT_LM3533) += lm3533_bl.o > diff --git a/drivers/video/backlight/ktd3137.c b/drivers/video/backlight/ktd3137.c > new file mode 100644 > index 000000000000..a3ff334b8d46 > --- /dev/null > +++ b/drivers/video/backlight/ktd3137.c > @@ -0,0 +1,262 @@ > > +static int ktd3137_init(struct ktd3137 *ktd) > +{ > + u32 val = KTD3137_CONTROL_DEFAULT | KTD3137_CONTROL_LINEAR; > + int ret; > + > + ret = regmap_write(ktd->regmap, KTD3137_REG_CONTROL, val); Nitpicking but val seems a bit pointless here. > + if (ret) > + return ret; > + > + ret = regmap_write(ktd->regmap, KTD3137_REG_PWM, KTD3137_PWM_DEFAULT); > + if (ret) > + return ret; > + > + ret = regmap_write(ktd->regmap, KTD3137_REG_RAMP_ON, KTD3137_RAMP_DEFAULT); > + if (ret) > + return ret; > + > + ret = regmap_write(ktd->regmap, KTD3137_REG_TRANS_RAMP, 0x00); > + if (ret) > + return ret; > + > + return regmap_update_bits(ktd->regmap, KTD3137_REG_MODE, > + KTD3137_MODE_CURRENT_MASK, ktd->led_current); > +} > > +static int ktd3137_probe(struct i2c_client *client) > +{ > + struct backlight_device *backlight_dev; > + struct backlight_properties props = { }; > + struct ktd3137 *ktd; > + u32 val; > + int ret; > + > + ktd = devm_kzalloc(&client->dev, sizeof(*ktd), GFP_KERNEL); > + if (!ktd) > + return -ENOMEM; > + > + ktd->dev = &client->dev; > + > + ret = devm_regulator_get_enable(ktd->dev, "vin"); > + if (ret) > + return dev_err_probe(ktd->dev, ret, "failed to power up\n"); > + > + ktd->enable_gpio = devm_gpiod_get_optional(ktd->dev, "enable", > + GPIOD_OUT_HIGH); > + if (IS_ERR(ktd->enable_gpio)) > + return dev_err_probe(ktd->dev, PTR_ERR(ktd->enable_gpio), > + "failed to get enable gpio\n"); > + > + /* HWEN should stay HIGH for at least 150us before I2C can be used */ > + fsleep(150); > + > + ktd->regmap = devm_regmap_init_i2c(client, &ktd3137_regmap_config); > + if (IS_ERR(ktd->regmap)) > + return dev_err_probe(ktd->dev, PTR_ERR(ktd->regmap), > + "failed to init regmap\n"); > + > + ret = regmap_read(ktd->regmap, KTD3137_REG_DEV_ID, &val); > + if (ret) > + return dev_err_probe(ktd->dev, ret, "failed to read chip id\n"); > + > + if (val != KTD3137_DEV_ID_A && val != KTD3137_DEV_ID_B) > + return dev_err_probe(ktd->dev, -ENODEV, > + "unsupported chip id: 0x%02x\n", val); > + > + ret = ktd3137_parse_dt(ktd); > + if (ret) > + return ret; > + > + ret = ktd3137_init(ktd); > + if (ret) > + return dev_err_probe(ktd->dev, ret, "failed to init chip\n"); > + > + props.type = BACKLIGHT_RAW; > + props.max_brightness = KTD3137_MAX_BRIGHTNESS; > + props.brightness = KTD3137_DEFAULT_BRIGHTNESS; No need for KTD3137_DEFAULT_BRIGHTNESS. Just use KTD3137_MAX_BRIGHTNESS. > + props.scale = BACKLIGHT_SCALE_LINEAR; > + device_property_read_u32(ktd->dev, "default-brightness", &props.brightness); > + > + backlight_dev = devm_backlight_device_register(ktd->dev, > + "ktd3137-backlight", > + ktd->dev, ktd, > + &ktd3137_backlight_ops, > + &props); > + if (IS_ERR(backlight_dev)) > + return dev_err_probe(ktd->dev, PTR_ERR(backlight_dev), > + "failed to register backlight device\n"); dev_err_cast_probe() > + > + i2c_set_clientdata(client, backlight_dev); > + return backlight_update_status(backlight_dev); > +} > + > +static void ktd3137_remove(struct i2c_client *client) > +{ > + struct backlight_device *backlight_dev = i2c_get_clientdata(client); > + struct ktd3137 *ktd = bl_get_data(backlight_dev); > + > + backlight_dev->props.brightness = 0; > + backlight_update_status(backlight_dev); > + > + gpiod_set_value_cansleep(ktd->enable_gpio, 0); Is this needed? > +} Daniel. ```