platform/x86: Add WMI driver for Redmibook keyboard

This driver implements support for various Fn keys (like Cut) and Xiaomi
specific AI button.

Reviewed-by: Armin Wolf <W_Armin@gmx.de>
Signed-off-by: Gladyshev Ilya <foxido@foxido.dev>
Link: https://lore.kernel.org/r/20250820174140.41410-1-foxido@foxido.dev
[ij: use BIT(8) instead of 0x00000100]
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

MAINTAINERS

@@ -21253,6 +21253,12 @@ S:	Maintained
 T:	git https://github.com/pkshih/rtw.git
 F:	drivers/net/wireless/realtek/rtw89/
 
+REDMIBOOK WMI DRIVERS
+M:	Gladyshev Ilya <foxido@foxido.dev>
+L:	platform-driver-x86@vger.kernel.org
+S:	Maintained
+F:	drivers/platform/x86/redmi-wmi.c
+
 REDPINE WIRELESS DRIVER
 L:	linux-wireless@vger.kernel.org
 S:	Orphan

drivers/platform/x86/Kconfig

@@ -118,6 +118,18 @@ config XIAOMI_WMI
 	  To compile this driver as a module, choose M here: the module will
 	  be called xiaomi-wmi.
 
+config REDMI_WMI
+	tristate "Redmibook WMI key driver"
+	depends on ACPI_WMI
+	depends on INPUT
+	select INPUT_SPARSEKMAP
+	help
+	  Say Y here if you want support for WMI-based hotkey events on
+	  Xiaomi Redmibook devices.
+
+	  To compile this driver as a module, choose M here: the module will
+	  be called redmi-wmi.
+
 config GIGABYTE_WMI
 	tristate "Gigabyte WMI temperature driver"
 	depends on ACPI_WMI

drivers/platform/x86/Makefile

@@ -13,6 +13,7 @@ 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-$(CONFIG_REDMI_WMI)			+= redmi-wmi.o
 obj-$(CONFIG_GIGABYTE_WMI)		+= gigabyte-wmi.o
 
 # Acer

drivers/platform/x86/redmi-wmi.c

@@ -0,0 +1,130 @@
+// SPDX-License-Identifier: GPL-2.0
+/* WMI driver for Xiaomi Redmibooks */
+
+#include <linux/acpi.h>
+#include <linux/bits.h>
+#include <linux/device.h>
+#include <linux/input.h>
+#include <linux/input/sparse-keymap.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/unaligned.h>
+#include <linux/wmi.h>
+
+#include <uapi/linux/input-event-codes.h>
+
+#define WMI_REDMIBOOK_KEYBOARD_EVENT_GUID "46C93E13-EE9B-4262-8488-563BCA757FEF"
+
+#define AI_KEY_VALUE_MASK BIT(8)
+
+static const struct key_entry redmi_wmi_keymap[] = {
+	{KE_KEY, 0x00000201,	{KEY_SELECTIVE_SCREENSHOT}},
+	{KE_KEY, 0x00000301,	{KEY_ALL_APPLICATIONS}},
+	{KE_KEY, 0x00001b01,	{KEY_SETUP}},
+
+	/* AI button has code for each position */
+	{KE_KEY, 0x00011801,	{KEY_ASSISTANT}},
+	{KE_KEY, 0x00011901,	{KEY_ASSISTANT}},
+
+	/* Keyboard backlight */
+	{KE_IGNORE, 0x00000501, {}},
+	{KE_IGNORE, 0x00800501, {}},
+	{KE_IGNORE, 0x00050501, {}},
+	{KE_IGNORE, 0x000a0501, {}},
+
+	{KE_END}
+};
+
+struct redmi_wmi {
+	struct input_dev *input_dev;
+	/* Protects the key event sequence */
+	struct mutex key_lock;
+};
+
+static int redmi_wmi_probe(struct wmi_device *wdev, const void *context)
+{
+	struct redmi_wmi *data;
+	int err;
+
+	/* Init dev */
+	data = devm_kzalloc(&wdev->dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	dev_set_drvdata(&wdev->dev, data);
+
+	err = devm_mutex_init(&wdev->dev, &data->key_lock);
+	if (err)
+		return err;
+
+	data->input_dev = devm_input_allocate_device(&wdev->dev);
+	if (!data->input_dev)
+		return -ENOMEM;
+
+	data->input_dev->name = "Redmibook WMI keys";
+	data->input_dev->phys = "wmi/input0";
+
+	err = sparse_keymap_setup(data->input_dev, redmi_wmi_keymap, NULL);
+	if (err)
+		return err;
+
+	return input_register_device(data->input_dev);
+}
+
+static void redmi_wmi_notify(struct wmi_device *wdev, union acpi_object *obj)
+{
+	struct key_entry *entry;
+	struct redmi_wmi *data = dev_get_drvdata(&wdev->dev);
+	bool autorelease = true;
+	u32 payload;
+	int value = 1;
+
+	if (obj->type != ACPI_TYPE_BUFFER) {
+		dev_err(&wdev->dev, "Bad response type %u\n", obj->type);
+		return;
+	}
+
+	if (obj->buffer.length < 32) {
+		dev_err(&wdev->dev, "Invalid buffer length %u\n", obj->buffer.length);
+		return;
+	}
+
+	payload = get_unaligned_le32(obj->buffer.pointer);
+	entry = sparse_keymap_entry_from_scancode(data->input_dev, payload);
+
+	if (!entry) {
+		dev_dbg(&wdev->dev, "Unknown WMI event with payload %u", payload);
+		return;
+	}
+
+	/* AI key quirk */
+	if (entry->keycode == KEY_ASSISTANT) {
+		value = !(payload & AI_KEY_VALUE_MASK);
+		autorelease = false;
+	}
+
+	guard(mutex)(&data->key_lock);
+	sparse_keymap_report_entry(data->input_dev, entry, value, autorelease);
+}
+
+static const struct wmi_device_id redmi_wmi_id_table[] = {
+	{ WMI_REDMIBOOK_KEYBOARD_EVENT_GUID, NULL },
+	{ }
+};
+
+static struct wmi_driver redmi_wmi_driver = {
+	.driver = {
+		.name = "redmi-wmi",
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
+	},
+	.id_table = redmi_wmi_id_table,
+	.probe = redmi_wmi_probe,
+	.notify = redmi_wmi_notify,
+	.no_singleton = true,
+};
+module_wmi_driver(redmi_wmi_driver);
+
+MODULE_DEVICE_TABLE(wmi, redmi_wmi_id_table);
+MODULE_AUTHOR("Gladyshev Ilya <foxido@foxido.dev>");
+MODULE_DESCRIPTION("Redmibook WMI driver");
+MODULE_LICENSE("GPL");