platform/x86: dell-privacy: Add support for Dell hardware privacy

add support for Dell privacy driver for the Dell units equipped
hardware privacy design, which protect users privacy of audio and
camera from hardware level. Once the audio or camera privacy mode
activated, any applications will not get any audio or video stream
when user pressed ctrl+F4 hotkey, audio privacy mode will be
enabled, micmute led will be also changed accordingly
The micmute led is fully controlled by hardware & EC(embedded controller)
and camera mute hotkey is Ctrl+F9. Currently design only emits
SW_CAMERA_LENS_COVER event while the camera lens shutter will be
changed by EC & HW(hardware) control

*The flow is like this:
1) User presses key. HW does stuff with this key (timeout timer is started)
2) WMI event is emitted from BIOS to kernel
3) WMI event is received by dell-privacy
4) KEY_MICMUTE emitted from dell-privacy
5) Userland picks up key and modifies kcontrol for SW mute
6) Codec kernel driver catches and calls ledtrig_audio_set
7) dell-privacy notifies EC, the timeout is cancelled and the HW mute
   is activated. If the EC is not notified then the HW mic mute will
   activate when the timeout triggers, just a bit later than with the
   active ack.
Signed-off-by: Perry Yuan <perry_yuan@dell.com>
Link: https://lore.kernel.org/r/20210506115605.1504-1-Perry_Yuan@Dell.com
[hdegoede@redhat.com: Rework Kconfig/Makefile bits + other small fixups]
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

Documentation/ABI/testing/sysfs-platform-dell-privacy-wmi

+What:		/sys/bus/wmi/devices/6932965F-1671-4CEB-B988-D3AB0A901919/dell_privacy_supported_type
+Date:		Apr 2021
+KernelVersion:	5.13
+Contact:	"perry.yuan@dell.com>"
+Description:
+		Display which dell hardware level privacy devices are supported
+		“Dell Privacy” is a set of HW, FW, and SW features to enhance
+		Dell’s commitment to platform privacy for MIC, Camera, and
+		ePrivacy screens.
+		The supported hardware privacy devices are:
+Attributes:
+		Microphone Mute:
+				Identifies the local microphone can be muted by hardware, no applications
+				is available to capture system mic sound
+
+		Camera Shutter:
+				Identifies camera shutter controlled by hardware, which is a micromechanical
+				shutter assembly that is built onto the camera module to block capturing images
+				from outside the laptop
+
+		supported:
+				The privacy device is supported by this system
+
+		unsupported:
+				The privacy device is not supported on this system
+
+		For example to check which privacy devices are supported:
+
+		# cat /sys/bus/wmi/drivers/dell-privacy/6932965F-1671-4CEB-B988-D3AB0A901919/dell_privacy_supported_type
+		[Microphone Mute] [supported]
+		[Camera Shutter] [supported]
+		[ePrivacy Screen] [unsupported]
+
+What:		/sys/bus/wmi/devices/6932965F-1671-4CEB-B988-D3AB0A901919/dell_privacy_current_state
+Date:		Apr 2021
+KernelVersion:	5.13
+Contact:	"perry.yuan@dell.com>"
+Description:
+		Allow user space to check current dell privacy device state.
+		Describes the Device State class exposed by BIOS which can be
+		consumed by various applications interested in knowing the Privacy
+		feature capabilities
+Attributes:
+		muted:
+			Identifies the privacy device is turned off and cannot send stream to OS applications
+
+		unmuted:
+			Identifies the privacy device is turned on ,audio or camera driver can get
+			stream from mic and camera module to OS applications
+
+		For example to check all supported current privacy device states:
+
+		# cat /sys/bus/wmi/drivers/dell-privacy/6932965F-1671-4CEB-B988-D3AB0A901919/dell_privacy_current_state
+		[Microphone] [unmuted]
+		[Camera Shutter] [unmuted]

MAINTAINERS

@@ -5172,6 +5172,13 @@ M:	Pali Rohár <pali@kernel.org>
 S:	Maintained
 F:	drivers/platform/x86/dell/dell-wmi-base.c
 
+DELL WMI HARDWARE PRIVACY SUPPORT
+M:	Perry Yuan <Perry.Yuan@dell.com>
+L:	Dell.Client.Kernel@dell.com
+L:	platform-driver-x86@vger.kernel.org
+S:	Maintained
+F:	drivers/platform/x86/dell/dell-wmi-privacy.c
+
 DELTA ST MEDIA DRIVER
 M:	Hugues Fruchet <hugues.fruchet@foss.st.com>
 L:	linux-media@vger.kernel.org

drivers/platform/x86/dell/Kconfig

@@ -53,6 +53,7 @@ config DELL_LAPTOP
 	depends on BACKLIGHT_CLASS_DEVICE
 	depends on ACPI_VIDEO || ACPI_VIDEO = n
 	depends on RFKILL || RFKILL = n
+	depends on DELL_WMI || DELL_WMI = n
 	depends on SERIO_I8042
 	depends on DELL_SMBIOS
 	select POWER_SUPPLY
@@ -164,6 +165,14 @@ config DELL_WMI
 	  To compile this driver as a module, choose M here: the module will
 	  be called dell-wmi.
 
+config DELL_WMI_PRIVACY
+	bool "Dell WMI Hardware Privacy Support"
+	depends on DELL_WMI
+	depends on LEDS_TRIGGER_AUDIO
+	help
+	  This option adds integration with the "Dell Hardware Privacy"
+	  feature of Dell laptops to the dell-wmi driver.
+
 config DELL_WMI_AIO
 	tristate "WMI Hotkeys for Dell All-In-One series"
 	default m

drivers/platform/x86/dell/Makefile

@@ -16,6 +16,7 @@ dell-smbios-$(CONFIG_DELL_SMBIOS_SMM)	+= dell-smbios-smm.o
 obj-$(CONFIG_DELL_SMO8800)		+= dell-smo8800.o
 obj-$(CONFIG_DELL_WMI)			+= dell-wmi.o
 dell-wmi-objs				:= dell-wmi-base.o
+dell-wmi-$(CONFIG_DELL_WMI_PRIVACY)	+= dell-wmi-privacy.o
 obj-$(CONFIG_DELL_WMI_AIO)		+= dell-wmi-aio.o
 obj-$(CONFIG_DELL_WMI_DESCRIPTOR)	+= dell-wmi-descriptor.o
 obj-$(CONFIG_DELL_WMI_LED)		+= dell-wmi-led.o

drivers/platform/x86/dell/dell-laptop.c

@@ -31,6 +31,8 @@
 #include "dell-rbtn.h"
 #include "dell-smbios.h"
 
+#include "dell-wmi-privacy.h"
+
 struct quirk_entry {
 	bool touchpad_led;
 	bool kbd_led_not_present;
@@ -90,6 +92,7 @@ static struct rfkill *wifi_rfkill;
 static struct rfkill *bluetooth_rfkill;
 static struct rfkill *wwan_rfkill;
 static bool force_rfkill;
+static bool micmute_led_registered;
 
 module_param(force_rfkill, bool, 0444);
 MODULE_PARM_DESC(force_rfkill, "enable rfkill on non whitelisted models");
@@ -2205,11 +2208,13 @@ static int __init dell_init(void)
 	dell_laptop_register_notifier(&dell_laptop_notifier);
 
 	if (dell_smbios_find_token(GLOBAL_MIC_MUTE_DISABLE) &&
-	    dell_smbios_find_token(GLOBAL_MIC_MUTE_ENABLE)) {
+	    dell_smbios_find_token(GLOBAL_MIC_MUTE_ENABLE) &&
+	    !dell_privacy_has_mic_mute()) {
 		micmute_led_cdev.brightness = ledtrig_audio_get(LED_AUDIO_MICMUTE);
 		ret = led_classdev_register(&platform_device->dev, &micmute_led_cdev);
 		if (ret < 0)
 			goto fail_led;
+		micmute_led_registered = true;
 	}
 
 	if (acpi_video_get_backlight_type() != acpi_backlight_vendor)
@@ -2257,6 +2262,7 @@ static int __init dell_init(void)
 fail_get_brightness:
 	backlight_device_unregister(dell_backlight_device);
 fail_backlight:
+	if (micmute_led_registered)
 		led_classdev_unregister(&micmute_led_cdev);
 fail_led:
 	dell_cleanup_rfkill();
@@ -2278,6 +2284,7 @@ static void __exit dell_exit(void)
 		touchpad_led_exit();
 	kbd_led_exit();
 	backlight_device_unregister(dell_backlight_device);
+	if (micmute_led_registered)
 		led_classdev_unregister(&micmute_led_cdev);
 	dell_cleanup_rfkill();
 	if (platform_device) {

drivers/platform/x86/dell/dell-wmi-base.c

@@ -27,6 +27,7 @@
 #include <acpi/video.h>
 #include "dell-smbios.h"
 #include "dell-wmi-descriptor.h"
+#include "dell-wmi-privacy.h"
 
 MODULE_AUTHOR("Matthew Garrett <mjg@redhat.com>");
 MODULE_AUTHOR("Pali Rohár <pali@kernel.org>");
@@ -427,7 +428,6 @@ static void dell_wmi_notify(struct wmi_device *wdev,
 
 		switch (buffer_entry[1]) {
 		case 0x0000: /* One key pressed or event occurred */
-		case 0x0012: /* Event with extended data occurred */
 			if (len > 2)
 				dell_wmi_process_key(wdev, buffer_entry[1],
 						     buffer_entry[2]);
@@ -439,6 +439,13 @@ static void dell_wmi_notify(struct wmi_device *wdev,
 				dell_wmi_process_key(wdev, buffer_entry[1],
 						     buffer_entry[i]);
 			break;
+		case 0x0012:
+			if ((len > 4) && dell_privacy_process_event(buffer_entry[1], buffer_entry[3],
+								    buffer_entry[4]))
+				/* dell_privacy_process_event has handled the event */;
+			else if (len > 2)
+				dell_wmi_process_key(wdev, buffer_entry[1], buffer_entry[2]);
+			break;
 		default: /* Unknown event */
 			pr_info("Unknown WMI event type 0x%x\n",
 				(int)buffer_entry[1]);
@@ -747,6 +754,10 @@ static int __init dell_wmi_init(void)
 		}
 	}
 
+	err = dell_privacy_register_driver();
+	if (err)
+		return err;
+
 	return wmi_driver_register(&dell_wmi_driver);
 }
 late_initcall(dell_wmi_init);
@@ -757,6 +768,7 @@ static void __exit dell_wmi_exit(void)
 		dell_wmi_events_set_enabled(false);
 
 	wmi_driver_unregister(&dell_wmi_driver);
+	dell_privacy_unregister_driver();
 }
 module_exit(dell_wmi_exit);
 

drivers/platform/x86/dell/dell-wmi-privacy.c

+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Dell privacy notification driver
+ *
+ * Copyright (C) 2021 Dell Inc. All Rights Reserved.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/acpi.h>
+#include <linux/bitops.h>
+#include <linux/input.h>
+#include <linux/input/sparse-keymap.h>
+#include <linux/list.h>
+#include <linux/leds.h>
+#include <linux/module.h>
+#include <linux/wmi.h>
+
+#include "dell-wmi-privacy.h"
+
+#define DELL_PRIVACY_GUID "6932965F-1671-4CEB-B988-D3AB0A901919"
+#define MICROPHONE_STATUS		BIT(0)
+#define CAMERA_STATUS		        BIT(1)
+#define DELL_PRIVACY_AUDIO_EVENT  0x1
+#define DELL_PRIVACY_CAMERA_EVENT 0x2
+#define led_to_priv(c)       container_of(c, struct privacy_wmi_data, cdev)
+
+/*
+ * The wmi_list is used to store the privacy_priv struct with mutex protecting
+ */
+static LIST_HEAD(wmi_list);
+static DEFINE_MUTEX(list_mutex);
+
+struct privacy_wmi_data {
+	struct input_dev *input_dev;
+	struct wmi_device *wdev;
+	struct list_head list;
+	struct led_classdev cdev;
+	u32 features_present;
+	u32 last_status;
+};
+
+/* DELL Privacy Type */
+enum dell_hardware_privacy_type {
+	DELL_PRIVACY_TYPE_AUDIO = 0,
+	DELL_PRIVACY_TYPE_CAMERA,
+	DELL_PRIVACY_TYPE_SCREEN,
+	DELL_PRIVACY_TYPE_MAX,
+};
+
+static const char * const privacy_types[DELL_PRIVACY_TYPE_MAX] = {
+	[DELL_PRIVACY_TYPE_AUDIO] = "Microphone",
+	[DELL_PRIVACY_TYPE_CAMERA] = "Camera Shutter",
+	[DELL_PRIVACY_TYPE_SCREEN] = "ePrivacy Screen",
+};
+
+/*
+ * Keymap for WMI privacy events of type 0x0012
+ */
+static const struct key_entry dell_wmi_keymap_type_0012[] = {
+	/* privacy mic mute */
+	{ KE_KEY, 0x0001, { KEY_MICMUTE } },
+	/* privacy camera mute */
+	{ KE_SW,  0x0002, { SW_CAMERA_LENS_COVER } },
+	{ KE_END, 0},
+};
+
+bool dell_privacy_has_mic_mute(void)
+{
+	struct privacy_wmi_data *priv;
+
+	mutex_lock(&list_mutex);
+	priv = list_first_entry_or_null(&wmi_list,
+			struct privacy_wmi_data,
+			list);
+	mutex_unlock(&list_mutex);
+
+	return priv && (priv->features_present & BIT(DELL_PRIVACY_TYPE_AUDIO));
+}
+EXPORT_SYMBOL_GPL(dell_privacy_has_mic_mute);
+
+/*
+ * The flow of privacy event:
+ * 1) User presses key. HW does stuff with this key (timeout is started)
+ * 2) WMI event is emitted from BIOS
+ * 3) WMI event is received by dell-privacy
+ * 4) KEY_MICMUTE emitted from dell-privacy
+ * 5) Userland picks up key and modifies kcontrol for SW mute
+ * 6) Codec kernel driver catches and calls ledtrig_audio_set which will call
+ *    led_set_brightness() on the LED registered by dell_privacy_leds_setup()
+ * 7) dell-privacy notifies EC, the timeout is cancelled and the HW mute activates.
+ *    If the EC is not notified then the HW mic mute will activate when the timeout
+ *    triggers, just a bit later than with the active ack.
+ */
+bool dell_privacy_process_event(int type, int code, int status)
+{
+	struct privacy_wmi_data *priv;
+	const struct key_entry *key;
+	bool ret = false;
+
+	mutex_lock(&list_mutex);
+	priv = list_first_entry_or_null(&wmi_list,
+			struct privacy_wmi_data,
+			list);
+	if (!priv)
+		goto error;
+
+	key = sparse_keymap_entry_from_scancode(priv->input_dev, (type << 16) | code);
+	if (!key) {
+		dev_warn(&priv->wdev->dev, "Unknown key with type 0x%04x and code 0x%04x pressed\n",
+			type, code);
+		goto error;
+	}
+	dev_dbg(&priv->wdev->dev, "Key with type 0x%04x and code 0x%04x pressed\n", type, code);
+
+	switch (code) {
+	case DELL_PRIVACY_AUDIO_EVENT: /* Mic mute */
+	case DELL_PRIVACY_CAMERA_EVENT: /* Camera mute */
+		priv->last_status = status;
+		sparse_keymap_report_entry(priv->input_dev, key, 1, true);
+		ret = true;
+		break;
+	default:
+		dev_dbg(&priv->wdev->dev, "unknown event type 0x%04x 0x%04x\n", type, code);
+	}
+
+error:
+	mutex_unlock(&list_mutex);
+	return ret;
+}
+
+static ssize_t dell_privacy_supported_type_show(struct device *dev,
+					struct device_attribute *attr,
+					char *buf)
+{
+	struct privacy_wmi_data *priv = dev_get_drvdata(dev);
+	enum dell_hardware_privacy_type type;
+	u32 privacy_list;
+	int len = 0;
+
+	privacy_list = priv->features_present;
+	for (type = DELL_PRIVACY_TYPE_AUDIO; type < DELL_PRIVACY_TYPE_MAX; type++) {
+		if (privacy_list & BIT(type))
+			len += sysfs_emit_at(buf, len, "[%s] [supported]\n", privacy_types[type]);
+		else
+			len += sysfs_emit_at(buf, len, "[%s] [unsupported]\n", privacy_types[type]);
+	}
+
+	return len;
+}
+
+static ssize_t dell_privacy_current_state_show(struct device *dev,
+					struct device_attribute *attr,
+					char *buf)
+{
+	struct privacy_wmi_data *priv = dev_get_drvdata(dev);
+	u32 privacy_supported = priv->features_present;
+	enum dell_hardware_privacy_type type;
+	u32 privacy_state = priv->last_status;
+	int len = 0;
+
+	for (type = DELL_PRIVACY_TYPE_AUDIO; type < DELL_PRIVACY_TYPE_MAX; type++) {
+		if (privacy_supported & BIT(type)) {
+			if (privacy_state & BIT(type))
+				len += sysfs_emit_at(buf, len, "[%s] [unmuted]\n", privacy_types[type]);
+			else
+				len += sysfs_emit_at(buf, len, "[%s] [muted]\n", privacy_types[type]);
+		}
+	}
+
+	return len;
+}
+
+static DEVICE_ATTR_RO(dell_privacy_supported_type);
+static DEVICE_ATTR_RO(dell_privacy_current_state);
+
+static struct attribute *privacy_attributes[] = {
+	&dev_attr_dell_privacy_supported_type.attr,
+	&dev_attr_dell_privacy_current_state.attr,
+	NULL,
+};
+
+static const struct attribute_group privacy_attribute_group = {
+	.attrs = privacy_attributes
+};
+
+/*
+ * Describes the Device State class exposed by BIOS which can be consumed by
+ * various applications interested in knowing the Privacy feature capabilities.
+ * class DeviceState
+ * {
+ *  [key, read] string InstanceName;
+ *  [read] boolean ReadOnly;
+ *
+ *  [WmiDataId(1), read] uint32 DevicesSupported;
+ *   0 - None; 0x1 - Microphone; 0x2 - Camera; 0x4 - ePrivacy  Screen
+ *
+ *  [WmiDataId(2), read] uint32 CurrentState;
+ *   0 - Off; 1 - On; Bit0 - Microphone; Bit1 - Camera; Bit2 - ePrivacyScreen
+ * };
+ */
+static int get_current_status(struct wmi_device *wdev)
+{
+	struct privacy_wmi_data *priv = dev_get_drvdata(&wdev->dev);
+	union acpi_object *obj_present;
+	u32 *buffer;
+	int ret = 0;
+
+	if (!priv) {
+		dev_err(&wdev->dev, "dell privacy priv is NULL\n");
+		return -EINVAL;
+	}
+	/* check privacy support features and device states */
+	obj_present = wmidev_block_query(wdev, 0);
+	if (!obj_present) {
+		dev_err(&wdev->dev, "failed to read Binary MOF\n");
+		return -EIO;
+	}
+
+	if (obj_present->type != ACPI_TYPE_BUFFER) {
+		dev_err(&wdev->dev, "Binary MOF is not a buffer!\n");
+		ret = -EIO;
+		goto obj_free;
+	}
+	/*  Although it's not technically a failure, this would lead to
+	 *  unexpected behavior
+	 */
+	if (obj_present->buffer.length != 8) {
+		dev_err(&wdev->dev, "Dell privacy buffer has unexpected length (%d)!\n",
+				obj_present->buffer.length);
+		ret = -EINVAL;
+		goto obj_free;
+	}
+	buffer = (u32 *)obj_present->buffer.pointer;
+	priv->features_present = buffer[0];
+	priv->last_status = buffer[1];
+
+obj_free:
+	kfree(obj_present);
+	return ret;
+}
+
+static int dell_privacy_micmute_led_set(struct led_classdev *led_cdev,
+					enum led_brightness brightness)
+{
+	struct privacy_wmi_data *priv = led_to_priv(led_cdev);
+	static char *acpi_method = (char *)"ECAK";
+	acpi_status status;
+	acpi_handle handle;
+
+	handle = ec_get_handle();
+	if (!handle)
+		return -EIO;
+
+	if (!acpi_has_method(handle, acpi_method))
+		return -EIO;
+
+	status = acpi_evaluate_object(handle, acpi_method, NULL, NULL);
+	if (ACPI_FAILURE(status)) {
+		dev_err(&priv->wdev->dev, "Error setting privacy EC ack value: %s\n",
+				acpi_format_exception(status));
+		return -EIO;
+	}
+
+	return 0;
+}
+
+/*
+ * Pressing the mute key activates a time delayed circuit to physically cut
+ * off the mute. The LED is in the same circuit, so it reflects the true
+ * state of the HW mute.  The reason for the EC "ack" is so that software
+ * can first invoke a SW mute before the HW circuit is cut off.  Without SW
+ * cutting this off first does not affect the time delayed muting or status
+ * of the LED but there is a possibility of a "popping" noise.
+ *
+ * If the EC receives the SW ack, the circuit will be activated before the
+ * delay completed.
+ *
+ * Exposing as an LED device allows the codec drivers notification path to
+ * EC ACK to work
+ */
+static int dell_privacy_leds_setup(struct device *dev)
+{
+	struct privacy_wmi_data *priv = dev_get_drvdata(dev);
+
+	priv->cdev.name = "dell-privacy::micmute";
+	priv->cdev.max_brightness = 1;
+	priv->cdev.brightness_set_blocking = dell_privacy_micmute_led_set;
+	priv->cdev.default_trigger = "audio-micmute";
+	priv->cdev.brightness = ledtrig_audio_get(LED_AUDIO_MICMUTE);
+	return devm_led_classdev_register(dev, &priv->cdev);
+}
+
+static int dell_privacy_wmi_probe(struct wmi_device *wdev, const void *context)
+{
+	struct privacy_wmi_data *priv;
+	struct key_entry *keymap;
+	int ret, i;
+
+	ret = wmi_has_guid(DELL_PRIVACY_GUID);
+	if (!ret)
+		pr_debug("Unable to detect available Dell privacy devices!\n");
+
+	priv = devm_kzalloc(&wdev->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	dev_set_drvdata(&wdev->dev, priv);
+	priv->wdev = wdev;
+	/* create evdev passing interface */
+	priv->input_dev = devm_input_allocate_device(&wdev->dev);
+	if (!priv->input_dev)
+		return -ENOMEM;
+
+	/* remap the wmi keymap event to new keymap */
+	keymap = kcalloc(ARRAY_SIZE(dell_wmi_keymap_type_0012),
+			sizeof(struct key_entry), GFP_KERNEL);
+	if (!keymap)
+		return -ENOMEM;
+
+	/* remap the keymap code with Dell privacy key type 0x12 as prefix
+	 * KEY_MICMUTE scancode will be reported as 0x120001
+	 */
+	for (i = 0; i < ARRAY_SIZE(dell_wmi_keymap_type_0012); i++) {
+		keymap[i] = dell_wmi_keymap_type_0012[i];
+		keymap[i].code |= (0x0012 << 16);
+	}
+	ret = sparse_keymap_setup(priv->input_dev, keymap, NULL);
+	kfree(keymap);
+	if (ret)
+		return ret;
+
+	priv->input_dev->dev.parent = &wdev->dev;
+	priv->input_dev->name = "Dell Privacy Driver";
+	priv->input_dev->id.bustype = BUS_HOST;
+
+	ret = input_register_device(priv->input_dev);
+	if (ret)
+		return ret;
+
+	ret = get_current_status(priv->wdev);
+	if (ret)
+		return ret;
+
+	ret = devm_device_add_group(&wdev->dev, &privacy_attribute_group);
+	if (ret)
+		return ret;
+
+	if (priv->features_present & BIT(DELL_PRIVACY_TYPE_AUDIO)) {
+		ret = dell_privacy_leds_setup(&priv->wdev->dev);
+		if (ret)
+			return ret;
+	}
+	mutex_lock(&list_mutex);
+	list_add_tail(&priv->list, &wmi_list);
+	mutex_unlock(&list_mutex);
+	return 0;
+}
+
+static void dell_privacy_wmi_remove(struct wmi_device *wdev)
+{
+	struct privacy_wmi_data *priv = dev_get_drvdata(&wdev->dev);
+
+	mutex_lock(&list_mutex);
+	list_del(&priv->list);
+	mutex_unlock(&list_mutex);
+}
+
+static const struct wmi_device_id dell_wmi_privacy_wmi_id_table[] = {
+	{ .guid_string = DELL_PRIVACY_GUID },
+	{ },
+};
+
+static struct wmi_driver dell_privacy_wmi_driver = {
+	.driver = {
+		.name = "dell-privacy",
+	},
+	.probe = dell_privacy_wmi_probe,
+	.remove = dell_privacy_wmi_remove,
+	.id_table = dell_wmi_privacy_wmi_id_table,
+};
+
+int dell_privacy_register_driver(void)
+{
+	return wmi_driver_register(&dell_privacy_wmi_driver);
+}
+
+void dell_privacy_unregister_driver(void)
+{
+	wmi_driver_unregister(&dell_privacy_wmi_driver);
+}

drivers/platform/x86/dell/dell-wmi-privacy.h

+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Dell privacy notification driver
+ *
+ * Copyright (C) 2021 Dell Inc. All Rights Reserved.
+ */
+
+#ifndef _DELL_PRIVACY_WMI_H_
+#define _DELL_PRIVACY_WMI_H_
+
+#if IS_ENABLED(CONFIG_DELL_WMI_PRIVACY)
+bool dell_privacy_has_mic_mute(void);
+bool dell_privacy_process_event(int type, int code, int status);
+int dell_privacy_register_driver(void);
+void dell_privacy_unregister_driver(void);
+#else /* CONFIG_DELL_PRIVACY */
+static inline bool dell_privacy_has_mic_mute(void)
+{
+	return false;
+}
+
+static inline bool dell_privacy_process_event(int type, int code, int status)
+{
+	return false;
+}
+
+static inline int dell_privacy_register_driver(void)
+{
+	return 0;
+}
+
+static inline void dell_privacy_unregister_driver(void)
+{
+}
+#endif /* CONFIG_DELL_PRIVACY */
+#endif