platform/x86: add lenovo WMI camera button driver

Add lenovo WMI camera button driver to support camera button.
The Camera button is a GPIO device. This driver receives ACPI notifications
when the camera button is switched on/off. This driver is used in
Lenovo A70, it is a Computer integrated machine.

Signed-off-by: Ai Chao <aichao@kylinos.cn>
Link: https://lore.kernel.org/r/20240327082737.336992-1-aichao@kylinos.cn
Reviewed-by: Armin Wolf <W_Armin@gmx.de>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

drivers/platform/x86/Kconfig

@@ -996,6 +996,18 @@ config INSPUR_PLATFORM_PROFILE
 	To compile this driver as a module, choose M here: the module
 	will be called inspur-platform-profile.
 
+config LENOVO_WMI_CAMERA
+	tristate "Lenovo WMI Camera Button driver"
+	depends on ACPI_WMI
+	depends on INPUT
+	help
+	  This driver provides support for Lenovo camera button. The Camera
+	  button is a GPIO device. This driver receives ACPI notifications when
+	  the camera button is switched on/off.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called lenovo-wmi-camera.
+
 source "drivers/platform/x86/x86-android-tablets/Kconfig"
 
 config FW_ATTR_CLASS

drivers/platform/x86/Makefile

@@ -66,6 +66,7 @@ obj-$(CONFIG_SENSORS_HDAPS)	+= hdaps.o
 obj-$(CONFIG_THINKPAD_ACPI)	+= thinkpad_acpi.o
 obj-$(CONFIG_THINKPAD_LMI)	+= think-lmi.o
 obj-$(CONFIG_YOGABOOK)		+= lenovo-yogabook.o
+obj-$(CONFIG_LENOVO_WMI_CAMERA)	+= lenovo-wmi-camera.o
 
 # Intel
 obj-y				+= intel/

drivers/platform/x86/lenovo-wmi-camera.c

@@ -0,0 +1,127 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Lenovo WMI Camera Button Driver
+ *
+ * Author: Ai Chao <aichao@kylinos.cn>
+ * Copyright (C) 2024 KylinSoft Corporation.
+ */
+
+#include <linux/acpi.h>
+#include <linux/device.h>
+#include <linux/input.h>
+#include <linux/types.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/wmi.h>
+
+#define WMI_LENOVO_CAMERABUTTON_EVENT_GUID "50C76F1F-D8E4-D895-0A3D-62F4EA400013"
+
+struct lenovo_wmi_priv {
+	struct input_dev *idev;
+	struct mutex notify_lock;	/* lenovo WMI camera button notify lock */
+};
+
+enum {
+	SW_CAMERA_OFF	= 0,
+	SW_CAMERA_ON	= 1,
+};
+
+static void lenovo_wmi_notify(struct wmi_device *wdev, union acpi_object *obj)
+{
+	struct lenovo_wmi_priv *priv = dev_get_drvdata(&wdev->dev);
+	unsigned int keycode;
+	u8 camera_mode;
+
+	if (obj->type != ACPI_TYPE_BUFFER) {
+		dev_err(&wdev->dev, "Bad response type %u\n", obj->type);
+		return;
+	}
+
+	if (obj->buffer.length != 1) {
+		dev_err(&wdev->dev, "Invalid buffer length %u\n", obj->buffer.length);
+		return;
+	}
+
+	/*
+	 * obj->buffer.pointer[0] is camera mode:
+	 *      0 camera close
+	 *      1 camera open
+	 */
+	camera_mode = obj->buffer.pointer[0];
+	if (camera_mode > SW_CAMERA_ON) {
+		dev_err(&wdev->dev, "Unknown camera mode %u\n", camera_mode);
+		return;
+	}
+
+	mutex_lock(&priv->notify_lock);
+
+	keycode = camera_mode == SW_CAMERA_ON ?
+		   KEY_CAMERA_ACCESS_ENABLE : KEY_CAMERA_ACCESS_DISABLE;
+	input_report_key(priv->idev, keycode, 1);
+	input_sync(priv->idev);
+	input_report_key(priv->idev, keycode, 0);
+	input_sync(priv->idev);
+
+	mutex_unlock(&priv->notify_lock);
+}
+
+static int lenovo_wmi_probe(struct wmi_device *wdev, const void *context)
+{
+	struct lenovo_wmi_priv *priv;
+	int ret;
+
+	priv = devm_kzalloc(&wdev->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	dev_set_drvdata(&wdev->dev, priv);
+
+	priv->idev = devm_input_allocate_device(&wdev->dev);
+	if (!priv->idev)
+		return -ENOMEM;
+
+	priv->idev->name = "Lenovo WMI Camera Button";
+	priv->idev->phys = "wmi/input0";
+	priv->idev->id.bustype = BUS_HOST;
+	priv->idev->dev.parent = &wdev->dev;
+	input_set_capability(priv->idev, EV_KEY, KEY_CAMERA_ACCESS_ENABLE);
+	input_set_capability(priv->idev, EV_KEY, KEY_CAMERA_ACCESS_DISABLE);
+
+	ret = input_register_device(priv->idev);
+	if (ret)
+		return ret;
+
+	mutex_init(&priv->notify_lock);
+
+	return 0;
+}
+
+static void lenovo_wmi_remove(struct wmi_device *wdev)
+{
+	struct lenovo_wmi_priv *priv = dev_get_drvdata(&wdev->dev);
+
+	mutex_destroy(&priv->notify_lock);
+}
+
+static const struct wmi_device_id lenovo_wmi_id_table[] = {
+	{ .guid_string = WMI_LENOVO_CAMERABUTTON_EVENT_GUID },
+	{  }
+};
+MODULE_DEVICE_TABLE(wmi, lenovo_wmi_id_table);
+
+static struct wmi_driver lenovo_wmi_driver = {
+	.driver = {
+		.name = "lenovo-wmi-camera",
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
+	},
+	.id_table = lenovo_wmi_id_table,
+	.no_singleton = true,
+	.probe = lenovo_wmi_probe,
+	.notify = lenovo_wmi_notify,
+	.remove = lenovo_wmi_remove,
+};
+module_wmi_driver(lenovo_wmi_driver);
+
+MODULE_AUTHOR("Ai Chao <aichao@kylinos.cn>");
+MODULE_DESCRIPTION("Lenovo WMI Camera Button Driver");
+MODULE_LICENSE("GPL");