Re: [PATCH v2] platform/x86: add Xiaomi WMI key driver

[Armin Wolf <W_Armin@gmx.de>]

Am 22.10.26 um 20:56 schrieb Lucy Wong:

> Certain Xiaomi laptops expose extra function keys through a single WMI
> event GUID (B74AF83F-8B2F-4069-ACAC-36D176F62FC0). Unlike the existing
> xiaomi-wmi driver where each key has its own GUID, here all keys share
> one GUID and the event buffer encodes both an event type and a keycode:
>
>    buffer[1] = event type
>      0x02: press/release keys (5 keys with abstract icons)
>      0x03: firmware-handled toggles (touchpad, Fn lock)
>    buffer[2] = keycode within that type
>
> The keys with abstract icons are mapped to programmable macro keys for
> userspace to bind. The touchpad and Fn lock toggles, as well as the
> keyboard backlight level events, are handled by the firmware and are
> ignored.
>
> Link: https://lore.kernel.org/platform-driver-x86/20260601151404.93049-1-lucywong2778@gmail.com/
> Signed-off-by: Lucy Wong <lucywong2778@gmail.com>
> ---
> Changes in v2:
> - Convert to .notify_new and set .min_event_size
> - Ignore firmware-handled backlight and toggle events, which removes the
>    toggle deduplication state
> - Add the missing select INPUT_SPARSEKMAP
> - Name the event codes and align the defines
> - Add the dev_printk.h include
> ---
>   MAINTAINERS                            |   6 ++
>   drivers/platform/x86/Kconfig           |  12 +++
>   drivers/platform/x86/Makefile          |   1 +
>   drivers/platform/x86/xiaomi-wmi-keys.c | 123 +++++++++++++++++++++++++
>   4 files changed, 142 insertions(+)
>   create mode 100644 drivers/platform/x86/xiaomi-wmi-keys.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 839e39825455..7969b82c8315 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -29124,6 +29124,12 @@ F:	fs/xfs/
>   F:	include/uapi/linux/dqblk_xfs.h
>   F:	include/uapi/linux/fsmap.h
>   
> +XIAOMI WMI KEYS DRIVER
> +M:	Lucy Wong <lucywong2778@gmail.com>
> +L:	platform-driver-x86@vger.kernel.org
> +S:	Maintained
> +F:	drivers/platform/x86/xiaomi-wmi-keys.c
> +
>   XILINX AMS DRIVER
>   M:	Salih Erim <salih.erim@amd.com>
>   M:	Conall O'Griofa <conall.ogriofa@amd.com>
> diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
> index b54b5212b204..1e7128f88adf 100644
> --- a/drivers/platform/x86/Kconfig
> +++ b/drivers/platform/x86/Kconfig
> @@ -90,6 +90,18 @@ config XIAOMI_WMI
>   	  To compile this driver as a module, choose M here: the module will
>   	  be called xiaomi-wmi.
>   
> +config XIAOMI_WMI_KEYS
> +	tristate "Xiaomi WMI key events driver"
> +	depends on ACPI_WMI
> +	depends on INPUT
> +	select INPUT_SPARSEKMAP
> +	help
> +	  Say Y here if you want to support WMI-based hotkey events on certain
> +	  Xiaomi laptops.
> +
> +	  To compile this driver as a module, choose M here: the module will
> +	  be called xiaomi-wmi-keys.
> +
>   config REDMI_WMI
>   	tristate "Redmibook WMI key driver"
>   	depends on ACPI_WMI
> diff --git a/drivers/platform/x86/Makefile b/drivers/platform/x86/Makefile
> index 872ac3842391..d852bb0bf61b 100644
> --- a/drivers/platform/x86/Makefile
> +++ b/drivers/platform/x86/Makefile
> @@ -12,6 +12,7 @@ obj-$(CONFIG_HUAWEI_WMI)		+= huawei-wmi.o
>   obj-$(CONFIG_MXM_WMI)			+= mxm-wmi.o
>   obj-$(CONFIG_NVIDIA_WMI_EC_BACKLIGHT)	+= nvidia-wmi-ec-backlight.o
>   obj-$(CONFIG_XIAOMI_WMI)		+= xiaomi-wmi.o
> +obj-$(CONFIG_XIAOMI_WMI_KEYS)		+= xiaomi-wmi-keys.o
>   obj-$(CONFIG_REDMI_WMI)			+= redmi-wmi.o
>   obj-$(CONFIG_GIGABYTE_WMI)		+= gigabyte-wmi.o
>   obj-$(CONFIG_BITLAND_MIFS_WMI)		+= bitland-mifs-wmi.o
> diff --git a/drivers/platform/x86/xiaomi-wmi-keys.c b/drivers/platform/x86/xiaomi-wmi-keys.c
> new file mode 100644
> index 000000000000..a01ef01e501e
> --- /dev/null
> +++ b/drivers/platform/x86/xiaomi-wmi-keys.c
> @@ -0,0 +1,123 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Xiaomi laptop WMI hotkey driver
> + *
> + * Copyright (C) 2026 Lucy Wong <lucywong2778@gmail.com>
> + */
> +
> +#include <linux/device.h>
> +#include <linux/dev_printk.h>
> +#include <linux/input.h>
> +#include <linux/input/sparse-keymap.h>
> +#include <linux/module.h>
> +#include <linux/wmi.h>
> +
> +#define XIAOMI_WMI_EVENT_GUID	"B74AF83F-8B2F-4069-ACAC-36D176F62FC0"
> +
> +#define XIAOMI_EVENT_TYPE_KEY	0x02

Please also document event type 0x03 and 0x01. Does your device contain embedded BMOF data?
I would be interested in taking a look at it.

> +
> +#define XIAOMI_KEY_PRESS_FIRST	0x01
> +#define XIAOMI_KEY_COUNT	5
> +#define XIAOMI_KEY_RELEASE_FIRST	\
> +	(XIAOMI_KEY_PRESS_FIRST + XIAOMI_KEY_COUNT)
> +
> +struct xiaomi_wmi_keys_event {
> +	u8 reserved;
> +	u8 type;
> +	u8 code;
> +};
> +
> +struct xiaomi_wmi_keys {
> +	struct input_dev *input_dev;
> +};
> +
> +static const struct key_entry xiaomi_wmi_keys_keymap[] = {
> +	/* programmable keys with abstract icons */
> +	{ KE_KEY, 0x01, { KEY_MACRO1 } },
> +	{ KE_KEY, 0x02, { KEY_MACRO2 } },
> +	{ KE_KEY, 0x03, { KEY_MACRO3 } },
> +	{ KE_KEY, 0x04, { KEY_MACRO4 } },
> +	{ KE_KEY, 0x05, { KEY_MACRO5 } },
> +	{ KE_END, 0 },
> +};
> +
> +static int xiaomi_wmi_keys_probe(struct wmi_device *wdev, const void *context)
> +{
> +	struct xiaomi_wmi_keys *data;
> +	int ret;
> +
> +	data = devm_kzalloc(&wdev->dev, sizeof(*data), GFP_KERNEL);
> +	if (!data)
> +		return -ENOMEM;
> +	dev_set_drvdata(&wdev->dev, data);

You need a mutex to sync each invocation of sparse_keymap_report_event().

> +
> +	data->input_dev = devm_input_allocate_device(&wdev->dev);
> +	if (!data->input_dev)
> +		return -ENOMEM;
> +
> +	data->input_dev->name = "Xiaomi WMI keys";
> +	data->input_dev->phys = "wmi/input0";
> +	data->input_dev->id.bustype = BUS_HOST;
> +
> +	ret = sparse_keymap_setup(data->input_dev, xiaomi_wmi_keys_keymap, NULL);
> +	if (ret)
> +		return ret;
> +
> +	return input_register_device(data->input_dev);
> +}
> +
> +static void xiaomi_wmi_keys_notify(struct wmi_device *wdev,
> +				   const struct wmi_buffer *buffer)
> +{
> +	const struct xiaomi_wmi_keys_event *event = buffer->data;
> +	struct xiaomi_wmi_keys *data = dev_get_drvdata(&wdev->dev);

Reverse XMAS tree ordering please, move the above assignment to the top.

> +	unsigned int code;
> +	bool pressed;
> +
> +	/*
> +	 * Only the press/release keys are reported. Event types 0x01
> +	 * (backlight) and 0x03 (touchpad and Fn-lock toggles) are handled by
> +	 * the firmware and need no action from the driver.
> +	 */
> +	if (event->type != XIAOMI_EVENT_TYPE_KEY) {
> +		dev_dbg(&wdev->dev, "ignoring event type 0x%02x\n", event->type);
> +		return;
> +	}
> +
> +	if (event->code >= XIAOMI_KEY_PRESS_FIRST &&
> +	    event->code < XIAOMI_KEY_PRESS_FIRST + XIAOMI_KEY_COUNT) {
> +		code = event->code;
> +		pressed = true;
> +	} else if (event->code >= XIAOMI_KEY_RELEASE_FIRST &&
> +		   event->code < XIAOMI_KEY_RELEASE_FIRST + XIAOMI_KEY_COUNT) {
> +		code = event->code - XIAOMI_KEY_COUNT;
> +		pressed = false;
> +	} else {
> +		dev_dbg(&wdev->dev, "ignoring key code 0x%02x\n", event->code);

Maybe use dev_notice() here to notify users that a unknown key index was received.

> +		return;
> +	}
> +
> +	sparse_keymap_report_event(data->input_dev, code, pressed, false);
> +}
> +
> +static const struct wmi_device_id xiaomi_wmi_keys_id_table[] = {
> +	{ .guid_string = XIAOMI_WMI_EVENT_GUID },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(wmi, xiaomi_wmi_keys_id_table);
> +
> +static struct wmi_driver xiaomi_wmi_keys_driver = {
> +	.driver = {
> +		.name = "xiaomi-wmi-keys",

Please add .probe_type = PROBE_PREFER_ASYNCHRONOUS here.

Other than that the driver looks promising.

Thanks,
Armin Wolf

> +	},
> +	.id_table = xiaomi_wmi_keys_id_table,
> +	.min_event_size = sizeof(struct xiaomi_wmi_keys_event),
> +	.probe = xiaomi_wmi_keys_probe,
> +	.notify_new = xiaomi_wmi_keys_notify,
> +	.no_singleton = true,
> +};
> +module_wmi_driver(xiaomi_wmi_keys_driver);
> +
> +MODULE_AUTHOR("Lucy Wong <lucywong2778@gmail.com>");
> +MODULE_DESCRIPTION("Xiaomi laptop WMI hotkey driver");
> +MODULE_LICENSE("GPL");