platform/surface: aggregator: Move subsystem hub drivers to their own module

Split out subsystem device hub drivers into their own module. This
allows us to load the hub drivers separately from the registry, which
will help future DT/OF support.

While doing so, also remove a small bit of code duplication.

Signed-off-by: Maximilian Luz <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Reviewed-by: Hans de Goede <[e-mail]>
Signed-off-by: Hans de Goede <[e-mail]>

MAINTAINERS

···
 F:	include/linux/surface_aggregator/
 F:	include/uapi/linux/surface_aggregator/
 
+MICROSOFT SURFACE SYSTEM AGGREGATOR HUB DRIVER
+M:	Maximilian Luz <[e-mail]>
+L:	[e-mail]
+S:	Maintained
+F:	drivers/platform/surface/surface_aggregator_hub.c
+
 MICROTEK X6 SCANNER
 M:	Oliver Neukum <[e-mail]>
 S:	Maintained

drivers/platform/surface/Kconfig

···
 	  The provided interface is intended for debugging and development only,
 	  and should not be used otherwise.
 
+config SURFACE_AGGREGATOR_HUB
+	tristate "Surface System Aggregator Module Subsystem Device Hubs"
+	depends on SURFACE_AGGREGATOR
+	depends on SURFACE_AGGREGATOR_BUS
+	help
+	  Device-hub drivers for Surface System Aggregator Module (SSAM) subsystem
+	  devices.
+
+	  Provides subsystem hub drivers which manage client devices on various
+	  SSAM subsystems. In some subsystems, notably the BAS subsystem managing
+	  devices contained in the base of the Surface Book 3 and the KIP subsystem
+	  managing type-cover devices in the Surface Pro 8 and Surface Pro X,
+	  devices can be (hot-)removed. Hub devices and drivers are required to
+	  manage these subdevices.
+
+	  Devices managed via these hubs are:
+	  - Battery/AC devices (Surface Book 3).
+	  - HID input devices (7th-generation and later models with detachable
+	    input devices).
+
+	  Select M (recommended) or Y here if you want support for the above
+	  mentioned devices on the corresponding Surface models. Without this
+	  module, the respective devices mentioned above will not be instantiated
+	  and thus any functionality provided by them will be missing, even when
+	  drivers for these devices are present. This module only provides the
+	  respective subsystem hubs. Both drivers and device specification (e.g.
+	  via the Surface Aggregator Registry) for these devices still need to be
+	  selected via other options.
+
 config SURFACE_AGGREGATOR_REGISTRY
 	tristate "Surface System Aggregator Module Device Registry"
 	depends on SURFACE_AGGREGATOR
 	depends on SURFACE_AGGREGATOR_BUS
 	help
-	  Device-registry and device-hubs for Surface System Aggregator Module
-	  (SSAM) devices.
+	  Device-registry for Surface System Aggregator Module (SSAM) devices.
 
 	  Provides a module and driver which act as a device-registry for SSAM
 	  client devices that cannot be detected automatically, e.g. via ACPI.
-	  Such devices are instead provided via this registry and attached via
-	  device hubs, also provided in this module.
+	  Such devices are instead provided and managed via this registry.
 
 	  Devices provided via this registry are:
 	  - Platform profile (performance-/cooling-mode) device (5th- and later

drivers/platform/surface/Makefile

···
 obj-$(CONFIG_SURFACE_ACPI_NOTIFY)	+= surface_acpi_notify.o
 obj-$(CONFIG_SURFACE_AGGREGATOR)	+= aggregator/
 obj-$(CONFIG_SURFACE_AGGREGATOR_CDEV)	+= surface_aggregator_cdev.o
+obj-$(CONFIG_SURFACE_AGGREGATOR_HUB)	+= surface_aggregator_hub.o
 obj-$(CONFIG_SURFACE_AGGREGATOR_REGISTRY) += surface_aggregator_registry.o
 obj-$(CONFIG_SURFACE_AGGREGATOR_TABLET_SWITCH) += surface_aggregator_tabletsw.o
 obj-$(CONFIG_SURFACE_DTX)		+= surface_dtx.o

drivers/platform/surface/surface_aggregator_hub.c

···
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Driver for Surface System Aggregator Module (SSAM) subsystem device hubs.
+ *
+ * Provides a driver for SSAM subsystems device hubs. This driver performs
+ * instantiation of the devices managed by said hubs and takes care of
+ * (hot-)removal.
+ *
+ * Copyright (C) 2020-2022 Maximilian Luz <[e-mail]>
+ */
+
+#include <linux/kernel.h>
+#include <linux/limits.h>
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/workqueue.h>
+
+#include <linux/surface_aggregator/device.h>
+
+
+/* -- SSAM generic subsystem hub driver framework. -------------------------- */
+
+enum ssam_hub_state {
+	SSAM_HUB_UNINITIALIZED,		/* Only set during initialization. */
+	SSAM_HUB_CONNECTED,
+	SSAM_HUB_DISCONNECTED,
+};
+
+enum ssam_hub_flags {
+	SSAM_HUB_HOT_REMOVED,
+};
+
+struct ssam_hub;
+
+struct ssam_hub_ops {
+	int (*get_state)(struct ssam_hub *hub, enum ssam_hub_state *state);
+};
+
+struct ssam_hub {
+	struct ssam_device *sdev;
+
+	enum ssam_hub_state state;
+	unsigned long flags;
+
+	struct delayed_work update_work;
+	unsigned long connect_delay;
+
+	struct ssam_event_notifier notif;
+	struct ssam_hub_ops ops;
+};
+
+struct ssam_hub_desc {
+	struct {
+		struct ssam_event_registry reg;
+		struct ssam_event_id id;
+		enum ssam_event_mask mask;
+	} event;
+
+	struct {
+		u32 (*notify)(struct ssam_event_notifier *nf, const struct ssam_event *event);
+		int (*get_state)(struct ssam_hub *hub, enum ssam_hub_state *state);
+	} ops;
+
+	unsigned long connect_delay_ms;
+};
+
+static void ssam_hub_update_workfn(struct work_struct *work)
+{
+	struct ssam_hub *hub = container_of(work, struct ssam_hub, update_work.work);
+	enum ssam_hub_state state;
+	int status = 0;
+
+	status = hub->ops.get_state(hub, &state);
+	if (status)
+		return;
+
+	/*
+	 * There is a small possibility that hub devices were hot-removed and
+	 * re-added before we were able to remove them here. In that case, both
+	 * the state returned by get_state() and the state of the hub will
+	 * equal SSAM_HUB_CONNECTED and we would bail early below, which would
+	 * leave child devices without proper (re-)initialization and the
+	 * hot-remove flag set.
+	 *
+	 * Therefore, we check whether devices have been hot-removed via an
+	 * additional flag on the hub and, in this case, override the returned
+	 * hub state. In case of a missed disconnect (i.e. get_state returned
+	 * "connected"), we further need to re-schedule this work (with the
+	 * appropriate delay) as the actual connect work submission might have
+	 * been merged with this one.
+	 *
+	 * This then leads to one of two cases: Either we submit an unnecessary
+	 * work item (which will get ignored via either the queue or the state
+	 * checks) or, in the unlikely case that the work is actually required,
+	 * double the normal connect delay.
+	 */
+	if (test_and_clear_bit(SSAM_HUB_HOT_REMOVED, &hub->flags)) {
+		if (state == SSAM_HUB_CONNECTED)
+			schedule_delayed_work(&hub->update_work, hub->connect_delay);
+
+		state = SSAM_HUB_DISCONNECTED;
+	}
+
+	if (hub->state == state)
+		return;
+	hub->state = state;
+
+	if (hub->state == SSAM_HUB_CONNECTED)
+		status = ssam_device_register_clients(hub->sdev);
+	else
+		ssam_remove_clients(&hub->sdev->dev);
+
+	if (status)
+		dev_err(&hub->sdev->dev, "failed to update hub child devices: %d\n", status);
+}
+
+static int ssam_hub_mark_hot_removed(struct device *dev, void *_data)
+{
+	struct ssam_device *sdev = to_ssam_device(dev);
+
+	if (is_ssam_device(dev))
+		ssam_device_mark_hot_removed(sdev);
+
+	return 0;
+}
+
+static void ssam_hub_update(struct ssam_hub *hub, bool connected)
+{
+	unsigned long delay;
+
+	/* Mark devices as hot-removed before we remove any. */
+	if (!connected) {
+		set_bit(SSAM_HUB_HOT_REMOVED, &hub->flags);
+		device_for_each_child_reverse(&hub->sdev->dev, NULL, ssam_hub_mark_hot_removed);
+	}
+
+	/*
+	 * Delay update when the base/keyboard cover is being connected to give
+	 * devices/EC some time to set up.
+	 */
+	delay = connected ? hub->connect_delay : 0;
+
+	schedule_delayed_work(&hub->update_work, delay);
+}
+
+static int __maybe_unused ssam_hub_resume(struct device *dev)
+{
+	struct ssam_hub *hub = dev_get_drvdata(dev);
+
+	schedule_delayed_work(&hub->update_work, 0);
+	return 0;
+}
+static SIMPLE_DEV_PM_OPS(ssam_hub_pm_ops, NULL, ssam_hub_resume);
+
+static int ssam_hub_probe(struct ssam_device *sdev)
+{
+	const struct ssam_hub_desc *desc;
+	struct ssam_hub *hub;
+	int status;
+
+	desc = ssam_device_get_match_data(sdev);
+	if (!desc) {
+		WARN(1, "no driver match data specified");
+		return -EINVAL;
+	}
+
+	hub = devm_kzalloc(&sdev->dev, sizeof(*hub), GFP_KERNEL);
+	if (!hub)
+		return -ENOMEM;
+
+	hub->sdev = sdev;
+	hub->state = SSAM_HUB_UNINITIALIZED;
+
+	hub->notif.base.priority = INT_MAX;  /* This notifier should run first. */
+	hub->notif.base.fn = desc->ops.notify;
+	hub->notif.event.reg = desc->event.reg;
+	hub->notif.event.id = desc->event.id;
+	hub->notif.event.mask = desc->event.mask;
+	hub->notif.event.flags = SSAM_EVENT_SEQUENCED;
+
+	hub->connect_delay = msecs_to_jiffies(desc->connect_delay_ms);
+	hub->ops.get_state = desc->ops.get_state;
+
+	INIT_DELAYED_WORK(&hub->update_work, ssam_hub_update_workfn);
+
+	ssam_device_set_drvdata(sdev, hub);
+
+	status = ssam_device_notifier_register(sdev, &hub->notif);
+	if (status)
+		return status;
+
+	schedule_delayed_work(&hub->update_work, 0);
+	return 0;
+}
+
+static void ssam_hub_remove(struct ssam_device *sdev)
+{
+	struct ssam_hub *hub = ssam_device_get_drvdata(sdev);
+
+	ssam_device_notifier_unregister(sdev, &hub->notif);
+	cancel_delayed_work_sync(&hub->update_work);
+	ssam_remove_clients(&sdev->dev);
+}
+
+
+/* -- SSAM base-subsystem hub driver. --------------------------------------- */
+
+/*
+ * Some devices (especially battery) may need a bit of time to be fully usable
+ * after being (re-)connected. This delay has been determined via
+ * experimentation.
+ */
+#define SSAM_BASE_UPDATE_CONNECT_DELAY		2500
+
+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_hub *hub, enum ssam_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_HUB_CONNECTED;
+	else
+		*state = SSAM_HUB_DISCONNECTED;
+
+	return 0;
+}
+
+static u32 ssam_base_hub_notif(struct ssam_event_notifier *nf, const struct ssam_event *event)
+{
+	struct ssam_hub *hub = container_of(nf, struct ssam_hub, notif);
+
+	if (event->command_id != SSAM_EVENT_BAS_CID_CONNECTION)
+		return 0;
+
+	if (event->length < 1) {
+		dev_err(&hub->sdev->dev, "unexpected payload size: %u\n", event->length);
+		return 0;
+	}
+
+	ssam_hub_update(hub, event->data[0]);
+
+	/*
+	 * 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 const struct ssam_hub_desc base_hub = {
+	.event = {
+		.reg = SSAM_EVENT_REGISTRY_SAM,
+		.id = {
+			.target_category = SSAM_SSH_TC_BAS,
+			.instance = 0,
+		},
+		.mask = SSAM_EVENT_MASK_NONE,
+	},
+	.ops = {
+		.notify = ssam_base_hub_notif,
+		.get_state = ssam_base_hub_query_state,
+	},
+	.connect_delay_ms = SSAM_BASE_UPDATE_CONNECT_DELAY,
+};
+
+
+/* -- SSAM KIP-subsystem hub driver. ---------------------------------------- */
+
+/*
+ * Some devices may need a bit of time to be fully usable after being
+ * (re-)connected. This delay has been determined via experimentation.
+ */
+#define SSAM_KIP_UPDATE_CONNECT_DELAY		250
+
+#define SSAM_EVENT_KIP_CID_CONNECTION		0x2c
+
+SSAM_DEFINE_SYNC_REQUEST_R(__ssam_kip_query_state, u8, {
+	.target_category = SSAM_SSH_TC_KIP,
+	.target_id       = 0x01,
+	.command_id      = 0x2c,
+	.instance_id     = 0x00,
+});
+
+static int ssam_kip_hub_query_state(struct ssam_hub *hub, enum ssam_hub_state *state)
+{
+	int status;
+	u8 connected;
+
+	status = ssam_retry(__ssam_kip_query_state, hub->sdev->ctrl, &connected);
+	if (status < 0) {
+		dev_err(&hub->sdev->dev, "failed to query KIP connection state: %d\n", status);
+		return status;
+	}
+
+	*state = connected ? SSAM_HUB_CONNECTED : SSAM_HUB_DISCONNECTED;
+	return 0;
+}
+
+static u32 ssam_kip_hub_notif(struct ssam_event_notifier *nf, const struct ssam_event *event)
+{
+	struct ssam_hub *hub = container_of(nf, struct ssam_hub, notif);
+
+	if (event->command_id != SSAM_EVENT_KIP_CID_CONNECTION)
+		return 0;	/* Return "unhandled". */
+
+	if (event->length < 1) {
+		dev_err(&hub->sdev->dev, "unexpected payload size: %u\n", event->length);
+		return 0;
+	}
+
+	ssam_hub_update(hub, event->data[0]);
+	return SSAM_NOTIF_HANDLED;
+}
+
+static const struct ssam_hub_desc kip_hub = {
+	.event = {
+		.reg = SSAM_EVENT_REGISTRY_SAM,
+		.id = {
+			.target_category = SSAM_SSH_TC_KIP,
+			.instance = 0,
+		},
+		.mask = SSAM_EVENT_MASK_TARGET,
+	},
+	.ops = {
+		.notify = ssam_kip_hub_notif,
+		.get_state = ssam_kip_hub_query_state,
+	},
+	.connect_delay_ms = SSAM_KIP_UPDATE_CONNECT_DELAY,
+};
+
+
+/* -- Driver registration. -------------------------------------------------- */
+
+static const struct ssam_device_id ssam_hub_match[] = {
+	{ SSAM_VDEV(HUB, 0x01, SSAM_SSH_TC_KIP, 0x00), (unsigned long)&kip_hub  },
+	{ SSAM_VDEV(HUB, 0x02, SSAM_SSH_TC_BAS, 0x00), (unsigned long)&base_hub },
+	{ }
+};
+MODULE_DEVICE_TABLE(ssam, ssam_hub_match);
+
+static struct ssam_device_driver ssam_subsystem_hub_driver = {
+	.probe = ssam_hub_probe,
+	.remove = ssam_hub_remove,
+	.match_table = ssam_hub_match,
+	.driver = {
+		.name = "surface_aggregator_subsystem_hub",
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
+		.pm = &ssam_hub_pm_ops,
+	},
+};
+module_ssam_device_driver(ssam_subsystem_hub_driver);
+
+MODULE_AUTHOR("Maximilian Luz <[e-mail]>");
+MODULE_DESCRIPTION("Subsystem device hub driver for Surface System Aggregator Module");
+MODULE_LICENSE("GPL");

drivers/platform/surface/surface_aggregator_registry.c

···
 
 #include <linux/acpi.h>
 #include <linux/kernel.h>
-#include <linux/limits.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
 #include <linux/property.h>
 #include <linux/types.h>
-#include <linux/workqueue.h>
 
-#include <linux/surface_aggregator/controller.h>
 #include <linux/surface_aggregator/device.h>
 
 
···
 };
 
 
-/* -- SSAM generic subsystem hub driver framework. -------------------------- */
-
-enum ssam_hub_state {
-	SSAM_HUB_UNINITIALIZED,		/* Only set during initialization. */
-	SSAM_HUB_CONNECTED,
-	SSAM_HUB_DISCONNECTED,
-};
-
-enum ssam_hub_flags {
-	SSAM_HUB_HOT_REMOVED,
-};
-
-struct ssam_hub {
-	struct ssam_device *sdev;
-
-	enum ssam_hub_state state;
-	unsigned long flags;
-
-	struct delayed_work update_work;
-	unsigned long connect_delay;
-
-	struct ssam_event_notifier notif;
-
-	int (*get_state)(struct ssam_hub *hub, enum ssam_hub_state *state);
-};
-
-static void ssam_hub_update_workfn(struct work_struct *work)
-{
-	struct ssam_hub *hub = container_of(work, struct ssam_hub, update_work.work);
-	enum ssam_hub_state state;
-	int status = 0;
-
-	status = hub->get_state(hub, &state);
-	if (status)
-		return;
-
-	/*
-	 * There is a small possibility that hub devices were hot-removed and
-	 * re-added before we were able to remove them here. In that case, both
-	 * the state returned by get_state() and the state of the hub will
-	 * equal SSAM_HUB_CONNECTED and we would bail early below, which would
-	 * leave child devices without proper (re-)initialization and the
-	 * hot-remove flag set.
-	 *
-	 * Therefore, we check whether devices have been hot-removed via an
-	 * additional flag on the hub and, in this case, override the returned
-	 * hub state. In case of a missed disconnect (i.e. get_state returned
-	 * "connected"), we further need to re-schedule this work (with the
-	 * appropriate delay) as the actual connect work submission might have
-	 * been merged with this one.
-	 *
-	 * This then leads to one of two cases: Either we submit an unnecessary
-	 * work item (which will get ignored via either the queue or the state
-	 * checks) or, in the unlikely case that the work is actually required,
-	 * double the normal connect delay.
-	 */
-	if (test_and_clear_bit(SSAM_HUB_HOT_REMOVED, &hub->flags)) {
-		if (state == SSAM_HUB_CONNECTED)
-			schedule_delayed_work(&hub->update_work, hub->connect_delay);
-
-		state = SSAM_HUB_DISCONNECTED;
-	}
-
-	if (hub->state == state)
-		return;
-	hub->state = state;
-
-	if (hub->state == SSAM_HUB_CONNECTED)
-		status = ssam_device_register_clients(hub->sdev);
-	else
-		ssam_remove_clients(&hub->sdev->dev);
-
-	if (status)
-		dev_err(&hub->sdev->dev, "failed to update hub child devices: %d\n", status);
-}
-
-static int ssam_hub_mark_hot_removed(struct device *dev, void *_data)
-{
-	struct ssam_device *sdev = to_ssam_device(dev);
-
-	if (is_ssam_device(dev))
-		ssam_device_mark_hot_removed(sdev);
-
-	return 0;
-}
-
-static void ssam_hub_update(struct ssam_hub *hub, bool connected)
-{
-	unsigned long delay;
-
-	/* Mark devices as hot-removed before we remove any. */
-	if (!connected) {
-		set_bit(SSAM_HUB_HOT_REMOVED, &hub->flags);
-		device_for_each_child_reverse(&hub->sdev->dev, NULL, ssam_hub_mark_hot_removed);
-	}
-
-	/*
-	 * Delay update when the base/keyboard cover is being connected to give
-	 * devices/EC some time to set up.
-	 */
-	delay = connected ? hub->connect_delay : 0;
-
-	schedule_delayed_work(&hub->update_work, delay);
-}
-
-static int __maybe_unused ssam_hub_resume(struct device *dev)
-{
-	struct ssam_hub *hub = dev_get_drvdata(dev);
-
-	schedule_delayed_work(&hub->update_work, 0);
-	return 0;
-}
-static SIMPLE_DEV_PM_OPS(ssam_hub_pm_ops, NULL, ssam_hub_resume);
-
-static int ssam_hub_setup(struct ssam_device *sdev, struct ssam_hub *hub)
-{
-	int status;
-
-	hub->sdev = sdev;
-	hub->state = SSAM_HUB_UNINITIALIZED;
-
-	INIT_DELAYED_WORK(&hub->update_work, ssam_hub_update_workfn);
-
-	ssam_device_set_drvdata(sdev, hub);
-
-	status = ssam_device_notifier_register(sdev, &hub->notif);
-	if (status)
-		return status;
-
-	schedule_delayed_work(&hub->update_work, 0);
-	return 0;
-}
-
-static void ssam_hub_remove(struct ssam_device *sdev)
-{
-	struct ssam_hub *hub = ssam_device_get_drvdata(sdev);
-
-	ssam_device_notifier_unregister(sdev, &hub->notif);
-	cancel_delayed_work_sync(&hub->update_work);
-	ssam_remove_clients(&sdev->dev);
-}
-
-
-/* -- SSAM base-hub driver. ------------------------------------------------- */
-
-/*
- * Some devices (especially battery) may need a bit of time to be fully usable
- * after being (re-)connected. This delay has been determined via
- * experimentation.
- */
-#define SSAM_BASE_UPDATE_CONNECT_DELAY		msecs_to_jiffies(2500)
-
-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_hub *hub, enum ssam_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_HUB_CONNECTED;
-	else
-		*state = SSAM_HUB_DISCONNECTED;
-
-	return 0;
-}
-
-static u32 ssam_base_hub_notif(struct ssam_event_notifier *nf, const struct ssam_event *event)
-{
-	struct ssam_hub *hub = container_of(nf, struct ssam_hub, notif);
-
-	if (event->command_id != SSAM_EVENT_BAS_CID_CONNECTION)
-		return 0;
-
-	if (event->length < 1) {
-		dev_err(&hub->sdev->dev, "unexpected payload size: %u\n", event->length);
-		return 0;
-	}
-
-	ssam_hub_update(hub, event->data[0]);
-
-	/*
-	 * 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 ssam_base_hub_probe(struct ssam_device *sdev)
-{
-	struct ssam_hub *hub;
-
-	hub = devm_kzalloc(&sdev->dev, sizeof(*hub), GFP_KERNEL);
-	if (!hub)
-		return -ENOMEM;
-
-	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;
-
-	hub->connect_delay = SSAM_BASE_UPDATE_CONNECT_DELAY;
-	hub->get_state = ssam_base_hub_query_state;
-
-	return ssam_hub_setup(sdev, hub);
-}
-
-static const struct ssam_device_id ssam_base_hub_match[] = {
-	{ SSAM_VDEV(HUB, 0x02, SSAM_SSH_TC_BAS, 0x00) },
-	{ },
-};
-
-static struct ssam_device_driver ssam_base_hub_driver = {
-	.probe = ssam_base_hub_probe,
-	.remove = ssam_hub_remove,
-	.match_table = ssam_base_hub_match,
-	.driver = {
-		.name = "surface_aggregator_base_hub",
-		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
-		.pm = &ssam_hub_pm_ops,
-	},
-};
-
-
-/* -- SSAM KIP-subsystem hub driver. ---------------------------------------- */
-
-/*
- * Some devices may need a bit of time to be fully usable after being
- * (re-)connected. This delay has been determined via experimentation.
- */
-#define SSAM_KIP_UPDATE_CONNECT_DELAY		msecs_to_jiffies(250)
-
-#define SSAM_EVENT_KIP_CID_CONNECTION		0x2c
-
-SSAM_DEFINE_SYNC_REQUEST_R(__ssam_kip_get_connection_state, u8, {
-	.target_category = SSAM_SSH_TC_KIP,
-	.target_id       = 0x01,
-	.command_id      = 0x2c,
-	.instance_id     = 0x00,
-});
-
-static int ssam_kip_get_connection_state(struct ssam_hub *hub, enum ssam_hub_state *state)
-{
-	int status;
-	u8 connected;
-
-	status = ssam_retry(__ssam_kip_get_connection_state, hub->sdev->ctrl, &connected);
-	if (status < 0) {
-		dev_err(&hub->sdev->dev, "failed to query KIP connection state: %d\n", status);
-		return status;
-	}
-
-	*state = connected ? SSAM_HUB_CONNECTED : SSAM_HUB_DISCONNECTED;
-	return 0;
-}
-
-static u32 ssam_kip_hub_notif(struct ssam_event_notifier *nf, const struct ssam_event *event)
-{
-	struct ssam_hub *hub = container_of(nf, struct ssam_hub, notif);
-
-	if (event->command_id != SSAM_EVENT_KIP_CID_CONNECTION)
-		return 0;	/* Return "unhandled". */
-
-	if (event->length < 1) {
-		dev_err(&hub->sdev->dev, "unexpected payload size: %u\n", event->length);
-		return 0;
-	}
-
-	ssam_hub_update(hub, event->data[0]);
-	return SSAM_NOTIF_HANDLED;
-}
-
-static int ssam_kip_hub_probe(struct ssam_device *sdev)
-{
-	struct ssam_hub *hub;
-
-	hub = devm_kzalloc(&sdev->dev, sizeof(*hub), GFP_KERNEL);
-	if (!hub)
-		return -ENOMEM;
-
-	hub->notif.base.priority = INT_MAX;  /* This notifier should run first. */
-	hub->notif.base.fn = ssam_kip_hub_notif;
-	hub->notif.event.reg = SSAM_EVENT_REGISTRY_SAM;
-	hub->notif.event.id.target_category = SSAM_SSH_TC_KIP,
-	hub->notif.event.id.instance = 0,
-	hub->notif.event.mask = SSAM_EVENT_MASK_TARGET;
-	hub->notif.event.flags = SSAM_EVENT_SEQUENCED;
-
-	hub->connect_delay = SSAM_KIP_UPDATE_CONNECT_DELAY;
-	hub->get_state = ssam_kip_get_connection_state;
-
-	return ssam_hub_setup(sdev, hub);
-}
-
-static const struct ssam_device_id ssam_kip_hub_match[] = {
-	{ SSAM_VDEV(HUB, 0x01, SSAM_SSH_TC_KIP, 0x00) },
-	{ },
-};
-
-static struct ssam_device_driver ssam_kip_hub_driver = {
-	.probe = ssam_kip_hub_probe,
-	.remove = ssam_hub_remove,
-	.match_table = ssam_kip_hub_match,
-	.driver = {
-		.name = "surface_kip_hub",
-		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
-		.pm = &ssam_hub_pm_ops,
-	},
-};
-
-
 /* -- SSAM platform/meta-hub driver. ---------------------------------------- */
 
 static const struct acpi_device_id ssam_platform_hub_match[] = {
···
 		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
 	},
 };
-
-
-/* -- Module initialization. ------------------------------------------------ */
-
-static int __init ssam_device_hub_init(void)
-{
-	int status;
-
-	status = platform_driver_register(&ssam_platform_hub_driver);
-	if (status)
-		goto err_platform;
-
-	status = ssam_device_driver_register(&ssam_base_hub_driver);
-	if (status)
-		goto err_base;
-
-	status = ssam_device_driver_register(&ssam_kip_hub_driver);
-	if (status)
-		goto err_kip;
-
-	return 0;
-
-err_kip:
-	ssam_device_driver_unregister(&ssam_base_hub_driver);
-err_base:
-	platform_driver_unregister(&ssam_platform_hub_driver);
-err_platform:
-	return status;
-}
-module_init(ssam_device_hub_init);
-
-static void __exit ssam_device_hub_exit(void)
-{
-	ssam_device_driver_unregister(&ssam_kip_hub_driver);
-	ssam_device_driver_unregister(&ssam_base_hub_driver);
-	platform_driver_unregister(&ssam_platform_hub_driver);
-}
-module_exit(ssam_device_hub_exit);
+module_platform_driver(ssam_platform_hub_driver);
 
 MODULE_AUTHOR("Maximilian Luz <[e-mail]>");
 MODULE_DESCRIPTION("Device-registry for Surface System Aggregator Module");