diff --git a/drivers/platform/surface/surface_aggregator_registry.c b/drivers/platform/surface/surface_aggregator_registry.c
index a051d941ad96..0d802804594c 100644
--- a/drivers/platform/surface/surface_aggregator_registry.c
+++ b/drivers/platform/surface/surface_aggregator_registry.c
@@ -11,9 +11,12 @@
 
 #include <linux/acpi.h>
 #include <linux/kernel.h>
+#include <linux/limits.h>
 #include <linux/module.h>
+#include <linux/mutex.h>
 #include <linux/platform_device.h>
 #include <linux/property.h>
+#include <linux/types.h>
 
 #include <linux/surface_aggregator/controller.h>
 #include <linux/surface_aggregator/device.h>
@@ -38,6 +41,12 @@ static const struct software_node ssam_node_root = {
 	.name = "ssam_platform_hub",
 };
 
+/* Base device hub (devices attached to Surface Book 3 base). */
+static const struct software_node ssam_node_hub_base = {
+	.name = "ssam:00:00:02:00:00",
+	.parent = &ssam_node_root,
+};
+
 /* Devices for Surface Book 2. */
 static const struct software_node *ssam_node_group_sb2[] = {
 	&ssam_node_root,
@@ -47,6 +56,7 @@ static const struct software_node *ssam_node_group_sb2[] = {
 /* Devices for Surface Book 3. */
 static const struct software_node *ssam_node_group_sb3[] = {
 	&ssam_node_root,
+	&ssam_node_hub_base,
 	NULL,
 };
 
@@ -177,6 +187,230 @@ static int ssam_hub_add_devices(struct device *parent, struct ssam_controller *c
 }
 
 
+/* -- SSAM base-hub driver. ------------------------------------------------- */
+
+enum ssam_base_hub_state {
+	SSAM_BASE_HUB_UNINITIALIZED,
+	SSAM_BASE_HUB_CONNECTED,
+	SSAM_BASE_HUB_DISCONNECTED,
+};
+
+struct ssam_base_hub {
+	struct ssam_device *sdev;
+
+	struct mutex lock;  /* Guards state update checks and transitions. */
+	enum ssam_base_hub_state state;
+
+	struct ssam_event_notifier notif;
+};
+
+static SSAM_DEFINE_SYNC_REQUEST_R(ssam_bas_query_opmode, u8, {
+	.target_category = SSAM_SSH_TC_BAS,
+	.target_id       = 0x01,
+	.command_id      = 0x0d,
+	.instance_id     = 0x00,
+});
+
+#define SSAM_BAS_OPMODE_TABLET		0x00
+#define SSAM_EVENT_BAS_CID_CONNECTION	0x0c
+
+static int ssam_base_hub_query_state(struct ssam_base_hub *hub, enum ssam_base_hub_state *state)
+{
+	u8 opmode;
+	int status;
+
+	status = ssam_retry(ssam_bas_query_opmode, hub->sdev->ctrl, &opmode);
+	if (status < 0) {
+		dev_err(&hub->sdev->dev, "failed to query base state: %d\n", status);
+		return status;
+	}
+
+	if (opmode != SSAM_BAS_OPMODE_TABLET)
+		*state = SSAM_BASE_HUB_CONNECTED;
+	else
+		*state = SSAM_BASE_HUB_DISCONNECTED;
+
+	return 0;
+}
+
+static ssize_t ssam_base_hub_state_show(struct device *dev, struct device_attribute *attr,
+					char *buf)
+{
+	struct ssam_base_hub *hub = dev_get_drvdata(dev);
+	bool connected;
+
+	mutex_lock(&hub->lock);
+	connected = hub->state == SSAM_BASE_HUB_CONNECTED;
+	mutex_unlock(&hub->lock);
+
+	return sysfs_emit(buf, "%d\n", connected);
+}
+
+static struct device_attribute ssam_base_hub_attr_state =
+	__ATTR(state, 0444, ssam_base_hub_state_show, NULL);
+
+static struct attribute *ssam_base_hub_attrs[] = {
+	&ssam_base_hub_attr_state.attr,
+	NULL,
+};
+
+const struct attribute_group ssam_base_hub_group = {
+	.attrs = ssam_base_hub_attrs,
+};
+
+static int __ssam_base_hub_update(struct ssam_base_hub *hub, enum ssam_base_hub_state new)
+{
+	struct fwnode_handle *node = dev_fwnode(&hub->sdev->dev);
+	int status = 0;
+
+	lockdep_assert_held(hub->lock);
+
+	if (hub->state == new)
+		return 0;
+	hub->state = new;
+
+	if (hub->state == SSAM_BASE_HUB_CONNECTED)
+		status = ssam_hub_add_devices(&hub->sdev->dev, hub->sdev->ctrl, node);
+	else
+		ssam_hub_remove_devices(&hub->sdev->dev);
+
+	if (status)
+		dev_err(&hub->sdev->dev, "failed to update base-hub devices: %d\n", status);
+
+	return status;
+}
+
+static int ssam_base_hub_update(struct ssam_base_hub *hub)
+{
+	enum ssam_base_hub_state state;
+	int status;
+
+	mutex_lock(&hub->lock);
+
+	status = ssam_base_hub_query_state(hub, &state);
+	if (!status)
+		status = __ssam_base_hub_update(hub, state);
+
+	mutex_unlock(&hub->lock);
+	return status;
+}
+
+static u32 ssam_base_hub_notif(struct ssam_event_notifier *nf, const struct ssam_event *event)
+{
+	struct ssam_base_hub *hub;
+	struct ssam_device *sdev;
+	enum ssam_base_hub_state new;
+
+	hub = container_of(nf, struct ssam_base_hub, notif);
+	sdev = hub->sdev;
+
+	if (event->command_id != SSAM_EVENT_BAS_CID_CONNECTION)
+		return 0;
+
+	if (event->length < 1) {
+		dev_err(&sdev->dev, "unexpected payload size: %u\n",
+			event->length);
+		return 0;
+	}
+
+	if (event->data[0])
+		new = SSAM_BASE_HUB_CONNECTED;
+	else
+		new = SSAM_BASE_HUB_DISCONNECTED;
+
+	mutex_lock(&hub->lock);
+	__ssam_base_hub_update(hub, new);
+	mutex_unlock(&hub->lock);
+
+	/*
+	 * Do not return SSAM_NOTIF_HANDLED: The event should be picked up and
+	 * consumed by the detachment system driver. We're just a (more or less)
+	 * silent observer.
+	 */
+	return 0;
+}
+
+static int __maybe_unused ssam_base_hub_resume(struct device *dev)
+{
+	return ssam_base_hub_update(dev_get_drvdata(dev));
+}
+static SIMPLE_DEV_PM_OPS(ssam_base_hub_pm_ops, NULL, ssam_base_hub_resume);
+
+static int ssam_base_hub_probe(struct ssam_device *sdev)
+{
+	struct ssam_base_hub *hub;
+	int status;
+
+	hub = devm_kzalloc(&sdev->dev, sizeof(*hub), GFP_KERNEL);
+	if (!hub)
+		return -ENOMEM;
+
+	mutex_init(&hub->lock);
+
+	hub->sdev = sdev;
+	hub->state = SSAM_BASE_HUB_UNINITIALIZED;
+
+	hub->notif.base.priority = INT_MAX;  /* This notifier should run first. */
+	hub->notif.base.fn = ssam_base_hub_notif;
+	hub->notif.event.reg = SSAM_EVENT_REGISTRY_SAM;
+	hub->notif.event.id.target_category = SSAM_SSH_TC_BAS,
+	hub->notif.event.id.instance = 0,
+	hub->notif.event.mask = SSAM_EVENT_MASK_NONE;
+	hub->notif.event.flags = SSAM_EVENT_SEQUENCED;
+
+	ssam_device_set_drvdata(sdev, hub);
+
+	status = ssam_notifier_register(sdev->ctrl, &hub->notif);
+	if (status)
+		goto err_register;
+
+	status = ssam_base_hub_update(hub);
+	if (status)
+		goto err_update;
+
+	status = sysfs_create_group(&sdev->dev.kobj, &ssam_base_hub_group);
+	if (status)
+		goto err_update;
+
+	return 0;
+
+err_update:
+	ssam_notifier_unregister(sdev->ctrl, &hub->notif);
+	ssam_hub_remove_devices(&sdev->dev);
+err_register:
+	mutex_destroy(&hub->lock);
+	return status;
+}
+
+static void ssam_base_hub_remove(struct ssam_device *sdev)
+{
+	struct ssam_base_hub *hub = ssam_device_get_drvdata(sdev);
+
+	sysfs_remove_group(&sdev->dev.kobj, &ssam_base_hub_group);
+
+	ssam_notifier_unregister(sdev->ctrl, &hub->notif);
+	ssam_hub_remove_devices(&sdev->dev);
+
+	mutex_destroy(&hub->lock);
+}
+
+static const struct ssam_device_id ssam_base_hub_match[] = {
+	{ SSAM_VDEV(HUB, 0x02, SSAM_ANY_IID, 0x00) },
+	{ },
+};
+
+static struct ssam_device_driver ssam_base_hub_driver = {
+	.probe = ssam_base_hub_probe,
+	.remove = ssam_base_hub_remove,
+	.match_table = ssam_base_hub_match,
+	.driver = {
+		.name = "surface_aggregator_base_hub",
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
+		.pm = &ssam_base_hub_pm_ops,
+	},
+};
+
+
 /* -- SSAM platform/meta-hub driver. ---------------------------------------- */
 
 static const struct acpi_device_id ssam_platform_hub_match[] = {
@@ -277,7 +511,32 @@ static struct platform_driver ssam_platform_hub_driver = {
 		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
 	},
 };
-module_platform_driver(ssam_platform_hub_driver);
+
+
+/* -- Module initialization. ------------------------------------------------ */
+
+static int __init ssam_device_hub_init(void)
+{
+	int status;
+
+	status = platform_driver_register(&ssam_platform_hub_driver);
+	if (status)
+		return status;
+
+	status = ssam_device_driver_register(&ssam_base_hub_driver);
+	if (status)
+		platform_driver_unregister(&ssam_platform_hub_driver);
+
+	return status;
+}
+module_init(ssam_device_hub_init);
+
+static void __exit ssam_device_hub_exit(void)
+{
+	ssam_device_driver_unregister(&ssam_base_hub_driver);
+	platform_driver_unregister(&ssam_platform_hub_driver);
+}
+module_exit(ssam_device_hub_exit);
 
 MODULE_AUTHOR("Maximilian Luz <luzmaximilian@gmail.com>");
 MODULE_DESCRIPTION("Device-registry for Surface System Aggregator Module");
