RE: [PATCH v3] platform/x86/amd: Introduce Halo Box RGB LED driver

From: Lin, Leo

Date: Thu May 14 2026 - 05:21:07 EST

AMD General

> -----Original Message-----
> From: Armin Wolf <W_Armin@xxxxxx>
> Sent: Wednesday, May 13, 2026 5:16 PM
> To: Lin, Leo <Leo.Lin@xxxxxxx>; Hans de Goede <hansg@xxxxxxxxxx>; Ilpo
> Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>; Mario Limonciello (AMD)
> <superm1@xxxxxxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx; platform-driver-x86@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH v3] platform/x86/amd: Introduce Halo Box RGB LED driver
>
> [You don't often get email from w_armin@xxxxxx. Learn why this is important at
> https://aka.ms/LearnAboutSenderIdentification ]
>
> Am 08.05.26 um 10:42 schrieb Yo-Jung Leo Lin (AMD):
> > The Halo Box features an RGB LED light bar that can be controlled
> > through WMI methods to display any color combination.
> >
> > The driver exposes the LED through the LED multicolor subsystem,
> > allowing userspace to control RGB values via sysfs:
> > /sys/class/leds/amd_halo:multicolor:status/multi_intensity
> > /sys/class/leds/amd_halo:multicolor:status/brightness
> >
> > Hardware interface:
> > - Three separate RGB channels (Red, Green, Blue)
> > - Each channel controlled via individual WMI method calls
> > - Value range: 0-100 (matching hardware range directly)
> >
> > Co-developed-by: Mario Limonciello (AMD) <superm1@xxxxxxxxxx>
> > Signed-off-by: Mario Limonciello (AMD) <superm1@xxxxxxxxxx>
> > Signed-off-by: Yo-Jung Leo Lin (AMD) <Leo.Lin@xxxxxxx>
> > ---
> > v2 -> v3:
> > - Re-introduce OF/OFF method: implement them with wmidev_invoke_method
> > - Explicitly call the ON method on brightness_set callback for
> > brightness != 0; call the OFF method when brightness == 0
> > - Turn off light bar if TURN_ON/SET_LIGHTBAR can't function normally
> > - Replace get_unaligned_le64 with casting and le16_to_cpu()
> > - Add an inline function (wmi_status_to_err) to convert WMI return
> > values to errno
> > - Use amd_halo_wmi_set_channel in probe to set default color
> > - Use devm_mutex_init() instead
> > - Remove unused includes
> > - Link to v2:
> > https://lore.kernel.org/r/20260504-halo-leds-v2-plus-v2-1-af027727605b
> > @amd.com
> >
> > v1 -> v2:
> > - Fix Kconfig dependencies
> > - Remove amd_halo_wmi_turn_off(). Handle the case where brightness=0 with
> the
> > same logic where brightness != 0
> > - Remove the brightness_get callback, because currently there isn't a
> > well-defined global bightness in hardware. Note that the sysfs brightness
> > stil works. It just caches the value last set.
> > - Convert to wmidev_invoke_method()
> > - Convert to ARRAY_SIZE()
> > - Convert some macros to enum
> > - Convert to devm_led_classdev_multicolor_register_ext()
> > - Rename sysfs path to amd_halo:multicolor:status
> > - Fold default LED colors setting in probe, before registration
> > - Add no_singleton option
> > - Make default RGB values into macros and adjust their values
> > ---
> > MAINTAINERS | 7 +
> > drivers/platform/x86/amd/Kconfig | 11 ++
> > drivers/platform/x86/amd/Makefile | 1 +
> > drivers/platform/x86/amd/amd_halo_led.c | 312
> ++++++++++++++++++++++++++++++++
> > 4 files changed, 331 insertions(+)
> >
> > diff --git a/MAINTAINERS b/MAINTAINERS index
> > c871acf2179c..464bd4d16461 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -1124,6 +1124,13 @@ F: drivers/char/hw_random/geode-rng.c
> > F: drivers/crypto/geode*
> > F: drivers/video/fbdev/geode/
> >
> > +AMD HALO BOX RGB LED DRIVER
> > +M: Mario Limonciello (AMD) <superm1@xxxxxxxxxx>
> > +R: Yo-Jung Leo Lin (AMD) <Leo.Lin@xxxxxxx>
> > +L: platform-driver-x86@xxxxxxxxxxxxxxx
> > +S: Supported
> > +F: drivers/platform/x86/amd/amd_halo_led.c
> > +
> > AMD HSMP DRIVER
> > M: Naveen Krishna Chatradhi <naveenkrishna.chatradhi@xxxxxxx>
> > R: Carlos Bilbao <carlos.bilbao@xxxxxxxxxx> diff --git
> > a/drivers/platform/x86/amd/Kconfig b/drivers/platform/x86/amd/Kconfig
> > index b813f9265368..a1a74ef6c859 100644
> > --- a/drivers/platform/x86/amd/Kconfig
> > +++ b/drivers/platform/x86/amd/Kconfig
> > @@ -34,6 +34,17 @@ config AMD_WBRF
> > This mechanism will only be activated on platforms that advertise a
> > need for it.
> >
> > +config AMD_HALO_LED
> > + tristate "AMD Halo Box RGB LED Driver"
> > + depends on ACPI_WMI && LEDS_CLASS_MULTICOLOR
> > + help
> > + This driver provides RGB LED control for AMD Halo Box devices
> > + through the LED multicolor subsystem. The Halo Box light bar can
> > + be controlled via sysfs to display any RGB color combination.
> > +
> > + To compile this driver as a module, choose M here: the module
> > + will be called amd_halo_led.
> > +
> > config AMD_ISP_PLATFORM
> > tristate "AMD ISP4 platform driver"
> > depends on I2C && X86_64 && ACPI diff --git
> > a/drivers/platform/x86/amd/Makefile
> > b/drivers/platform/x86/amd/Makefile
> > index f6ff0c837f34..2f467dbbfc8a 100644
> > --- a/drivers/platform/x86/amd/Makefile
> > +++ b/drivers/platform/x86/amd/Makefile
> > @@ -10,5 +10,6 @@ obj-$(CONFIG_AMD_PMC) += pmc/
> > obj-$(CONFIG_AMD_HSMP) += hsmp/
> > obj-$(CONFIG_AMD_PMF) += pmf/
> > obj-$(CONFIG_AMD_WBRF) += wbrf.o
> > +obj-$(CONFIG_AMD_HALO_LED) += amd_halo_led.o
> > obj-$(CONFIG_AMD_ISP_PLATFORM) += amd_isp4.o
> > obj-$(CONFIG_AMD_HFI) += hfi/
> > diff --git a/drivers/platform/x86/amd/amd_halo_led.c
> > b/drivers/platform/x86/amd/amd_halo_led.c
> > new file mode 100644
> > index 000000000000..632ccdf07ffe
> > --- /dev/null
> > +++ b/drivers/platform/x86/amd/amd_halo_led.c
> > @@ -0,0 +1,312 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * AMD Halo Box RGB LED Driver
> > + *
> > + * Copyright (C) 2026 Advanced Micro Devices, Inc.
> > + *
> > + * This driver provides RGB LED control for AMD Halo Box devices
> > +through
> > + * the LED multicolor subsystem. The Halo Box light bar can be
> > +controlled
> > + * via sysfs to display any RGB color combination.
> > + */
> > +
> > +#include <linux/led-class-multicolor.h> #include <linux/leds.h>
> > +#include <linux/module.h> #include <linux/mutex.h> #include
> > +<linux/wmi.h>
> > +
> > +#define AMD_HALO_GUID "081E747B-E028-4232-AF24-EAAEAB2B1E86"
> > +
> > +/* WMI method IDs from MOF */
> > +enum {
> > + AMD_HALO_WMI_GET_LIGHTBAR = 0x01,
> > + AMD_HALO_WMI_SET_LIGHTBAR,
> > + AMD_HALO_WMI_TURN_ON,
> > + AMD_HALO_WMI_TURN_OFF
> > +};
> > +
> > +/* Channel selectors for Arg0 */
> > +enum {
> > + AMD_HALO_CHANNEL_RED = 0x01,
> > + AMD_HALO_CHANNEL_GREEN,
> > + AMD_HALO_CHANNEL_BLUE
> > +};
> > +
> > +/* Status codes from spec */
> > +#define AMD_HALO_STATUS_SUCCESS 0x0000
> > +#define AMD_HALO_STATUS_INVALID_PARAM 0xFFFD
> > +
> > +/* Brightness uses 0-100 range */
> > +#define AMD_HALO_MAX_HW_BRIGHTNESS 100
> > +
> > +/* Default RGB brightness */
> > +#define AMD_HALO_DEFAULT_RED 50
> > +#define AMD_HALO_DEFAULT_GREEN 30
> > +#define AMD_HALO_DEFAULT_BLUE 30
> > +
> > +/**
> > + * struct amd_halo_led_data - Driver private data
> > + * @wdev: WMI device pointer
> > + * @led_mc: LED multicolor class device
> > + * @subled_info: RGB channel information
> > + * @lock: Mutex to protect WMI calls
> > + */
> > +struct amd_halo_led_data {
> > + struct wmi_device *wdev;
> > + struct led_classdev_mc led_mc;
> > + struct mc_subled subled_info[3];
> > + struct mutex lock; /* Protects WMI method calls */
> > +};
> > +
> > +struct amd_halo_wmi_args {
> > + u32 arg0;
> > + u32 arg1;
>
> Hi,
>
> those two arguments are little-endian integers, so please use
> __le32 instead of u32. This will also require you to use le32_to_cpu() and
> cpu_to_le32() when populating and accesssing this struct.
>
> > +};
> > +
> > +static inline int wmi_status_to_err(u16 status) {
> > + switch (status) {
> > + case AMD_HALO_STATUS_SUCCESS:
> > + return 0;
> > + case AMD_HALO_STATUS_INVALID_PARAM:
> > + return -EINVAL;
> > + default:
> > + return -EIO;
> > + }
> > +}
> > +
> > +static int __amd_halo_wmi_call(struct wmi_device *wdev,
> > + u32 method_id,
> > + u32 arg0,
> > + u32 arg1) {
> > + struct amd_halo_wmi_args args = {
> > + .arg0 = arg0,
> > + .arg1 = arg1,
> > + };
>
> Use cpu_to_le32() to ensure that the firmware receives little-endian integers.
>
> > + struct wmi_buffer input = {
> > + .length = sizeof(args),
> > + .data = &args,
> > + };
> > + struct wmi_buffer output = { 0 };
> > + u16 result_status;
> > + int ret;
> > +
> > + ret = wmidev_invoke_method(wdev, 0, method_id,
> > + &input, &output, sizeof(result_status));
> > + if (ret)
> > + return ret;
> > +
> > + /* Return buffer per spec: Bytes[0:1] = Status (little-endian) */
> > + result_status = le16_to_cpu(*(__le16 *)output.data);
> > + ret = wmi_status_to_err(result_status);
> > +
> > + kfree(output.data);
>
> You could use "__le16 *result_status __free(kfree) = output.data" here to avoid
> having to call kfree() manually. You can also move this declaration to the top for
> the sizeof() expression, as long as you initialize it with NULL.
>
> > + return ret;
> > +}
> > +
> > +/**
> > + * amd_halo_wmi_turn_on - Turn on all LED channels
> > + * @wdev: WMI device pointer
> > + *
> > + * Return: 0 on success, negative error code on failure */ static
> > +int amd_halo_wmi_turn_on(struct wmi_device *wdev) {
> > + return __amd_halo_wmi_call(wdev, AMD_HALO_WMI_TURN_ON, 0, 0); }
> > +
> > +/**
> > + * amd_halo_wmi_turn_off - Turn off all LED channels
> > + * @wdev: WMI device pointer
> > + *
> > + * Return: 0 on success, negative error code on failure */ static
> > +int amd_halo_wmi_turn_off(struct wmi_device *wdev) {
> > + return __amd_halo_wmi_call(wdev, AMD_HALO_WMI_TURN_OFF, 0, 0); }
> > +
> > +/**
> > + * amd_halo_wmi_set_channel - Set a single RGB channel value
> > + * @wdev: WMI device pointer
> > + * @channel: Channel selector (1=Red, 2=Green, 3=Blue)
> > + * @brightness: brightness to set (0-100)
> > + *
> > + * Return: 0 on success, negative error code on failure */ static
> > +int amd_halo_wmi_set_channel(struct wmi_device *wdev, u32 channel,
> > + u32 brightness) {
> > + if (channel < AMD_HALO_CHANNEL_RED ||
> > + channel > AMD_HALO_CHANNEL_BLUE ||
> > + brightness > AMD_HALO_MAX_HW_BRIGHTNESS)
> > + return -EINVAL;
> > +
> > + return __amd_halo_wmi_call(wdev, AMD_HALO_WMI_SET_LIGHTBAR,
> > + channel, brightness); }
> > +
> > +/**
> > + * amd_halo_brightness_set - Set LED brightness and color
> > + * @cdev: LED class device
> > + * @brightness: Brightness value
> > + *
> > + * Return: 0 on success, negative error code on failure */ static
> > +int amd_halo_brightness_set(struct led_classdev *cdev,
> > + enum led_brightness brightness) {
> > + struct led_classdev_mc *mc_cdev = lcdev_to_mccdev(cdev);
> > + struct amd_halo_led_data *data = container_of(mc_cdev,
> > + struct amd_halo_led_data,
> > + led_mc);
> > + u32 red_hw, green_hw, blue_hw;
> > + int ret;
> > +
> > + guard(mutex)(&data->lock);
> > +
> > + led_mc_calc_color_components(mc_cdev, brightness);
> > +
> > + if (brightness == 0)
> > + return amd_halo_wmi_turn_off(data->wdev);
>
> When turning on this LED after turning it off, the RGB color might be wrong for a
> short amount of time. I suggest that you still update the RGB color even when the
> brightness is 0.

Hi Armin,

Thanks for the review. The BIOS clears RGB values to 0 when the off method is called, so I think there won't be staled RGB values here.

Will fix all the other things (including the ones Ilpo mentioned) in the next version.

BR,
Leo

>
> > +
> > + red_hw = mc_cdev->subled_info[0].brightness;
> > + green_hw = mc_cdev->subled_info[1].brightness;
> > + blue_hw = mc_cdev->subled_info[2].brightness;
> > +
> > + ret = amd_halo_wmi_turn_on(data->wdev);
> > + if (ret)
> > + goto out;
> > +
> > + ret = amd_halo_wmi_set_channel(data->wdev,
> AMD_HALO_CHANNEL_RED,
> > + red_hw);
> > + if (ret)
> > + goto out;
> > +
> > + ret = amd_halo_wmi_set_channel(data->wdev,
> AMD_HALO_CHANNEL_GREEN,
> > + green_hw);
> > + if (ret)
> > + goto out;
> > +
> > + ret = amd_halo_wmi_set_channel(data->wdev,
> AMD_HALO_CHANNEL_BLUE,
> > + blue_hw);
> > + if (ret)
> > + goto out;
> > +
> > + return 0;
> > +
> > +out:
> > + /*
> > + * Consider the light bar non-functional if TURN_ON or SET_LIGHTBAR
> failed.
> > + * Attempt to turn the LED off completely as clean-up.
> > + */
> > + if (amd_halo_wmi_turn_off(data->wdev))
> > + dev_warn_ratelimited(&data->wdev->dev, "Failed to turn
> > +LED off on cleanup\n");
> > +
> > + return ret;
> > +}
> > +
> > +/**
> > + * amd_halo_probe - Driver probe function
> > + * @wdev: WMI device
> > + * @context: Context data (unused)
> > + *
> > + * Return: 0 on success, negative error code on failure */ static
> > +int amd_halo_probe(struct wmi_device *wdev, const void *context) {
> > + struct led_init_data led_init_data = {
> > + .devicename = "amd_halo",
> > + .default_label = "multicolor:" LED_FUNCTION_STATUS,
> > + .devname_mandatory = true
> > + };
> > + struct amd_halo_led_data *data;
> > + int ret;
> > +
> > + data = devm_kzalloc(&wdev->dev, sizeof(*data), GFP_KERNEL);
> > + if (!data)
> > + return -ENOMEM;
> > +
> > + ret = devm_mutex_init(&wdev->dev, &data->lock);
> > + if (ret)
> > + return ret;
> > +
> > + data->wdev = wdev;
> > + dev_set_drvdata(&wdev->dev, data);
> > +
> > + data->subled_info[0].color_index = LED_COLOR_ID_RED;
> > + data->subled_info[1].color_index = LED_COLOR_ID_GREEN;
> > + data->subled_info[2].color_index = LED_COLOR_ID_BLUE;
> > + data->subled_info[0].intensity = AMD_HALO_DEFAULT_RED;
> > + data->subled_info[1].intensity = AMD_HALO_DEFAULT_GREEN;
> > + data->subled_info[2].intensity = AMD_HALO_DEFAULT_BLUE;
> > +
> > + data->led_mc.led_cdev.brightness = AMD_HALO_MAX_HW_BRIGHTNESS;
> > + data->led_mc.led_cdev.max_brightness =
> AMD_HALO_MAX_HW_BRIGHTNESS;
> > + data->led_mc.led_cdev.brightness_set_blocking =
> amd_halo_brightness_set;
> > + data->led_mc.led_cdev.flags = LED_CORE_SUSPENDRESUME |
> LED_RETAIN_AT_SHUTDOWN;
> > + data->led_mc.num_colors = ARRAY_SIZE(data->subled_info);
> > + data->led_mc.subled_info = data->subled_info;
> > +
> > + ret = amd_halo_wmi_turn_on(wdev);
> > + if (ret)
> > + goto out;
> > +
> > + ret = amd_halo_wmi_set_channel(wdev, AMD_HALO_CHANNEL_RED,
> > + AMD_HALO_DEFAULT_RED);
> > + if (ret)
> > + goto out;
> > +
> > + ret = amd_halo_wmi_set_channel(wdev, AMD_HALO_CHANNEL_GREEN,
> > + AMD_HALO_DEFAULT_GREEN);
> > + if (ret)
> > + goto out;
> > +
> > + ret = amd_halo_wmi_set_channel(wdev, AMD_HALO_CHANNEL_BLUE,
> > + AMD_HALO_DEFAULT_BLUE);
> > + if (ret)
> > + goto out;
> > +
> > + ret = devm_led_classdev_multicolor_register_ext(&wdev->dev, &data-
> >led_mc,
> > + &led_init_data);
> > + if (ret)
> > + return dev_err_probe(&wdev->dev, ret,
> > + "Failed to register multicolor LED\n");
> > + return 0;
> > +
> > +out:
> > + /*
> > + * Attempt to turn LED off as a cleanup if either TURN_ON or
> SET_LIGHTBAR
> > + * fails. For probe failure due to non-WMI errors, keep the LED in the
> > + * default color.
> > + */
> > + dev_warn(&data->wdev->dev, "Light bar non-functional, turning it
> > +off\n");
> > +
> > + if (amd_halo_wmi_turn_off(data->wdev))
> > + dev_warn(&data->wdev->dev, "Failed to turn LED off on
> > + cleanup\n");
>
> I do not think that this cleanup is necessary during probe, please remove it and
> just return an error instead.
>
> Otherwise the driver seems good to me.
>
> Thanks,
> Armin Wolf
>
> > +
> > + return dev_err_probe(&wdev->dev, ret, "WMI call failed during
> > +probe!\n"); }
> > +
> > +static const struct wmi_device_id amd_halo_id_table[] = {
> > + { .guid_string = AMD_HALO_GUID },
> > + { }
> > +};
> > +MODULE_DEVICE_TABLE(wmi, amd_halo_id_table);
> > +
> > +static struct wmi_driver amd_halo_driver = {
> > + .driver = {
> > + .name = "amd_halo_led",
> > + },
> > + .id_table = amd_halo_id_table,
> > + .probe = amd_halo_probe,
> > + .no_singleton = true,
> > +};
> > +
> > +module_wmi_driver(amd_halo_driver);
> > +
> > +MODULE_AUTHOR("Mario Limonciello (AMD) <superm1@xxxxxxxxxx>");
> > +MODULE_AUTHOR("Yo-Jung Leo Lin (AMD) <Leo.Lin@xxxxxxx>");
> > +MODULE_DESCRIPTION("AMD Halo Box RGB LED Control Driver");
> > +MODULE_LICENSE("GPL");
> >
> > ---
> > base-commit: 39704f00f747aba3144289870b5fd8ac230a9aaf
> > change-id: 20260429-halo-leds-v2-plus-722c8083afe8
> >
> > Best regards,