Message-ID: <20250727223516.29244-1-foxido@foxido.dev>
Date: Mon, 28 Jul 2025 01:34:59 +0300
From: Gladyshev Ilya <foxido@...ido.dev>
To: foxido@...ido.dev
Cc: w_armin@....de,
	Hans de Goede <hansg@...nel.org>,
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
	linux-kernel@...r.kernel.org,
	platform-driver-x86@...r.kernel.org
Subject: [PATCH 1/1] Add WMI driver for Redmibook keyboard.

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

Signed-off-by: Gladyshev Ilya <foxido@...ido.dev>
---
 MAINTAINERS                      |   6 ++
 drivers/platform/x86/Kconfig     |  10 ++
 drivers/platform/x86/Makefile    |   1 +
 drivers/platform/x86/redmi-wmi.c | 164 +++++++++++++++++++++++++++++++
 4 files changed, 181 insertions(+)
 create mode 100644 drivers/platform/x86/redmi-wmi.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 10850512c118..b3956f3d2eb8 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -20965,6 +20965,12 @@ S:	Maintained
 T:	git https://github.com/pkshih/rtw.git
 F:	drivers/net/wireless/realtek/rtw89/
 
+REDMIBOOK WMI DRIVERS
+M:	Gladyshev Ilya <foxido@...ido.dev>
+L:	platform-driver-x86@...r.kernel.org
+S:	Maintained
+F:	drivers/platform/x86/redmi-wmi.c
+
 REDPINE WIRELESS DRIVER
 L:	linux-wireless@...r.kernel.org
 S:	Orphan
diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
index e5cbd58a99f3..b8d426e6b5a3 100644
--- a/drivers/platform/x86/Kconfig
+++ b/drivers/platform/x86/Kconfig
@@ -109,6 +109,16 @@ 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
+	help
+	  Say Y here if you want to support WMI-based keys on Redmibooks.
+
+	  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
diff --git a/drivers/platform/x86/Makefile b/drivers/platform/x86/Makefile
index abbc2644ff6d..56903d7408cd 100644
--- a/drivers/platform/x86/Makefile
+++ b/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
diff --git a/drivers/platform/x86/redmi-wmi.c b/drivers/platform/x86/redmi-wmi.c
new file mode 100644
index 000000000000..0bb6ea7b1081
--- /dev/null
+++ b/drivers/platform/x86/redmi-wmi.c
@@ -0,0 +1,164 @@
+// SPDX-License-Identifier: GPL-2.0
+/* WMI driver for Xiaomi Redmibooks */
+
+#include <linux/acpi.h>
+#include <linux/device.h>
+#include <linux/input.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/wmi.h>
+
+#include <uapi/linux/input-event-codes.h>
+
+#define WMI_REDMIBOOK_KEYBOARD_EVENT_GUID "46c93e13-ee9b-4262-8488-563bca757fef"
+
+/* Supported WMI keys ... */
+#define ACPI_CUT_PAYLOAD		0x00000201
+#define ACPI_ALL_APPS_PAYLOAD		0x00000301
+#define ACPI_SETUP_PAYLOAD		0x00001b01
+#define ACPI_CST_KEY_PRESS_PAYLOAD	0x00011801
+#define ACPI_CST_KEY_RELEASE_PAYLOAD	0x00011901
+
+/* ... and their mappings */
+#define WMI_CUT_KEY		KEY_PROG1
+#define WMI_ALL_APPS_KEY	KEY_ALL_APPLICATIONS
+#define WMI_SETUP_KEY		KEY_SETUP
+#define WMI_CST_KEY		KEY_ASSISTANT
+
+/* Keyboard backlight key (not supported yet) */
+#define BACKLIGHT_LEVEL_0_PAYLOAD	0x00000501
+#define BACKLIGHT_LEVEL_1_PAYLOAD	0x00800501
+#define BACKLIGHT_LEVEL_2_PAYLOAD	0x00050501
+#define BACKLIGHT_LEVEL_3_PAYLOAD	0x000a0501
+
+struct redmi_wmi {
+	struct input_dev *input_dev;
+	/* Protects the key event sequence */
+	struct mutex key_lock;
+};
+
+static void redmi_mutex_destroy(void *data)
+{
+	struct mutex *lock = data;
+
+	mutex_destroy(lock);
+}
+
+static int redmi_wmi_probe(struct wmi_device *wdev, const void *context)
+{
+	struct redmi_wmi *data;
+	int ret;
+
+	/* Init dev */
+	data = devm_kzalloc(&wdev->dev, sizeof(struct redmi_wmi), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	dev_set_drvdata(&wdev->dev, data);
+
+	/* Init mutex & setup destroy at exit */
+	mutex_init(&data->key_lock);
+	ret = devm_add_action_or_reset(&wdev->dev, redmi_mutex_destroy, &data->key_lock);
+	if (ret < 0)
+		return ret;
+
+	/* Setup input device */
+	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";
+
+	set_bit(EV_KEY, data->input_dev->evbit);
+
+	/* "Cut" key*/
+	set_bit(WMI_CUT_KEY, data->input_dev->keybit);
+	/* "All apps" key*/
+	set_bit(WMI_ALL_APPS_KEY, data->input_dev->keybit);
+	/* "Settings" key */
+	set_bit(WMI_SETUP_KEY, data->input_dev->keybit);
+	/* Custom (AI?) key */
+	set_bit(WMI_CST_KEY, data->input_dev->keybit);
+
+	return input_register_device(data->input_dev);
+}
+
+static void press_and_release_key(struct input_dev *dev, unsigned int code)
+{
+	input_report_key(dev, code, 1);
+	input_sync(dev);
+	input_report_key(dev, code, 0);
+	input_sync(dev);
+}
+
+static void redmi_wmi_notify(struct wmi_device *wdev, union acpi_object *obj)
+{
+	struct redmi_wmi *data = dev_get_drvdata(&wdev->dev);
+
+	if (obj->type != ACPI_TYPE_BUFFER) {
+		dev_err(&wdev->dev, "Bad response type %u\n", obj->type);
+		return;
+	}
+
+	if (obj->buffer.length < 4) {
+		dev_err(&wdev->dev, "Invalid buffer length %u\n", obj->buffer.length);
+		return;
+	}
+
+	/* For linearizability */
+	guard(mutex)(&data->key_lock);
+
+	u32 payload = ((u32 *)obj->buffer.pointer)[0];
+
+	switch (payload) {
+	case ACPI_CUT_PAYLOAD:
+		press_and_release_key(data->input_dev, WMI_CUT_KEY);
+		break;
+	case ACPI_ALL_APPS_PAYLOAD:
+		press_and_release_key(data->input_dev, WMI_ALL_APPS_KEY);
+		break;
+	case ACPI_SETUP_PAYLOAD:
+		press_and_release_key(data->input_dev, WMI_SETUP_KEY);
+		break;
+	case ACPI_CST_KEY_PRESS_PAYLOAD:
+		input_report_key(data->input_dev, WMI_CST_KEY, 1);
+		input_sync(data->input_dev);
+		break;
+	case ACPI_CST_KEY_RELEASE_PAYLOAD:
+		input_report_key(data->input_dev, WMI_CST_KEY, 0);
+		input_sync(data->input_dev);
+		break;
+	case BACKLIGHT_LEVEL_0_PAYLOAD:
+	case BACKLIGHT_LEVEL_1_PAYLOAD:
+	case BACKLIGHT_LEVEL_2_PAYLOAD:
+	case BACKLIGHT_LEVEL_3_PAYLOAD:
+		pr_debug("keyboard backlight WMI event, no action");
+		break;
+	default:
+		pr_debug("unsupported Redmibook WMI event with 4byte payload %u", payload);
+		break;
+	}
+}
+
+static const struct wmi_device_id redmi_wmi_id_table[] = {
+	{ .guid_string = WMI_REDMIBOOK_KEYBOARD_EVENT_GUID },
+	/* Terminating entry */
+	{ }
+};
+
+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@...ido.dev>");
+MODULE_DESCRIPTION("Redmibook WMI driver");
+MODULE_LICENSE("GPL");
-- 
2.50.0

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