drivers/platform/surface/surface_aggregator_tabletsw.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0+
 /*
  * Surface System Aggregator Module (SSAM) tablet mode switch driver.
  *
  * Copyright (C) 2022 Maximilian Luz <luzmaximilian@gmail.com>
  */

 #include <asm/unaligned.h>
 #include <linux/input.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/types.h>
 #include <linux/workqueue.h>

 #include <linux/surface_aggregator/controller.h>
 #include <linux/surface_aggregator/device.h>


 /* -- SSAM generic tablet switch driver framework. -------------------------- */

 struct ssam_tablet_sw;

 struct ssam_tablet_sw_ops {
 	int (*get_state)(struct ssam_tablet_sw *sw, u32 *state);
 	const char *(*state_name)(struct ssam_tablet_sw *sw, u32 state);
 	bool (*state_is_tablet_mode)(struct ssam_tablet_sw *sw, u32 state);
 };

 struct ssam_tablet_sw {
 	struct ssam_device *sdev;

 	u32 state;
 	struct work_struct update_work;
 	struct input_dev *mode_switch;

 	struct ssam_tablet_sw_ops ops;
 	struct ssam_event_notifier notif;
 };

 struct ssam_tablet_sw_desc {
 	struct {
 		const char *name;
 		const char *phys;
 	} dev;

 	struct {
 		u32 (*notify)(struct ssam_event_notifier *nf, const struct ssam_event *event);
 		int (*get_state)(struct ssam_tablet_sw *sw, u32 *state);
 		const char *(*state_name)(struct ssam_tablet_sw *sw, u32 state);
 		bool (*state_is_tablet_mode)(struct ssam_tablet_sw *sw, u32 state);
 	} ops;

 	struct {
 		struct ssam_event_registry reg;
 		struct ssam_event_id id;
 		enum ssam_event_mask mask;
 		u8 flags;
 	} event;
 };

 static ssize_t state_show(struct device *dev, struct device_attribute *attr, char *buf)
 {
 	struct ssam_tablet_sw *sw = dev_get_drvdata(dev);
 	const char *state = sw->ops.state_name(sw, sw->state);

 	return sysfs_emit(buf, "%s\n", state);
 }
 static DEVICE_ATTR_RO(state);

 static struct attribute *ssam_tablet_sw_attrs[] = {
 	&dev_attr_state.attr,
 	NULL,
 };

 static const struct attribute_group ssam_tablet_sw_group = {
 	.attrs = ssam_tablet_sw_attrs,
 };

 static void ssam_tablet_sw_update_workfn(struct work_struct *work)
 {
 	struct ssam_tablet_sw *sw = container_of(work, struct ssam_tablet_sw, update_work);
 	int tablet, status;
 	u32 state;

 	status = sw->ops.get_state(sw, &state);
 	if (status)
 		return;

 	if (sw->state == state)
 		return;
 	sw->state = state;

 	/* Send SW_TABLET_MODE event. */
 	tablet = sw->ops.state_is_tablet_mode(sw, state);
 	input_report_switch(sw->mode_switch, SW_TABLET_MODE, tablet);
 	input_sync(sw->mode_switch);
 }

 static int __maybe_unused ssam_tablet_sw_resume(struct device *dev)
 {
 	struct ssam_tablet_sw *sw = dev_get_drvdata(dev);

 	schedule_work(&sw->update_work);
 	return 0;
 }
 static SIMPLE_DEV_PM_OPS(ssam_tablet_sw_pm_ops, NULL, ssam_tablet_sw_resume);

 static int ssam_tablet_sw_probe(struct ssam_device *sdev)
 {
 	const struct ssam_tablet_sw_desc *desc;
 	struct ssam_tablet_sw *sw;
 	int tablet, status;

 	desc = ssam_device_get_match_data(sdev);
 	if (!desc) {
 		WARN(1, "no driver match data specified");
 		return -EINVAL;
 	}

 	sw = devm_kzalloc(&sdev->dev, sizeof(*sw), GFP_KERNEL);
 	if (!sw)
 		return -ENOMEM;

 	sw->sdev = sdev;

 	sw->ops.get_state = desc->ops.get_state;
 	sw->ops.state_name = desc->ops.state_name;
 	sw->ops.state_is_tablet_mode = desc->ops.state_is_tablet_mode;

 	INIT_WORK(&sw->update_work, ssam_tablet_sw_update_workfn);

 	ssam_device_set_drvdata(sdev, sw);

 	/* Get initial state. */
 	status = sw->ops.get_state(sw, &sw->state);
 	if (status)
 		return status;

 	/* Set up tablet mode switch. */
 	sw->mode_switch = devm_input_allocate_device(&sdev->dev);
 	if (!sw->mode_switch)
 		return -ENOMEM;

 	sw->mode_switch->name = desc->dev.name;
 	sw->mode_switch->phys = desc->dev.phys;
 	sw->mode_switch->id.bustype = BUS_HOST;
 	sw->mode_switch->dev.parent = &sdev->dev;

 	tablet = sw->ops.state_is_tablet_mode(sw, sw->state);
 	input_set_capability(sw->mode_switch, EV_SW, SW_TABLET_MODE);
 	input_report_switch(sw->mode_switch, SW_TABLET_MODE, tablet);

 	status = input_register_device(sw->mode_switch);
 	if (status)
 		return status;

 	/* Set up notifier. */
 	sw->notif.base.priority = 0;
 	sw->notif.base.fn = desc->ops.notify;
 	sw->notif.event.reg = desc->event.reg;
 	sw->notif.event.id = desc->event.id;
 	sw->notif.event.mask = desc->event.mask;
 	sw->notif.event.flags = SSAM_EVENT_SEQUENCED;

 	status = ssam_device_notifier_register(sdev, &sw->notif);
 	if (status)
 		return status;

 	status = sysfs_create_group(&sdev->dev.kobj, &ssam_tablet_sw_group);
 	if (status)
 		goto err;

 	/* We might have missed events during setup, so check again. */
 	schedule_work(&sw->update_work);
 	return 0;

 err:
 	ssam_device_notifier_unregister(sdev, &sw->notif);
 	cancel_work_sync(&sw->update_work);
 	return status;
 }

 static void ssam_tablet_sw_remove(struct ssam_device *sdev)
 {
 	struct ssam_tablet_sw *sw = ssam_device_get_drvdata(sdev);

 	sysfs_remove_group(&sdev->dev.kobj, &ssam_tablet_sw_group);

 	ssam_device_notifier_unregister(sdev, &sw->notif);
 	cancel_work_sync(&sw->update_work);
 }


 /* -- SSAM KIP tablet switch implementation. -------------------------------- */

 #define SSAM_EVENT_KIP_CID_COVER_STATE_CHANGED	0x1d

 enum ssam_kip_cover_state {
 	SSAM_KIP_COVER_STATE_DISCONNECTED  = 0x01,
 	SSAM_KIP_COVER_STATE_CLOSED        = 0x02,
 	SSAM_KIP_COVER_STATE_LAPTOP        = 0x03,
 	SSAM_KIP_COVER_STATE_FOLDED_CANVAS = 0x04,
 	SSAM_KIP_COVER_STATE_FOLDED_BACK   = 0x05,
 };

 static const char *ssam_kip_cover_state_name(struct ssam_tablet_sw *sw, u32 state)
 {
 	switch (state) {
 	case SSAM_KIP_COVER_STATE_DISCONNECTED:
 		return "disconnected";

 	case SSAM_KIP_COVER_STATE_CLOSED:
 		return "closed";

 	case SSAM_KIP_COVER_STATE_LAPTOP:
 		return "laptop";

 	case SSAM_KIP_COVER_STATE_FOLDED_CANVAS:
 		return "folded-canvas";

 	case SSAM_KIP_COVER_STATE_FOLDED_BACK:
 		return "folded-back";

 	default:
 		dev_warn(&sw->sdev->dev, "unknown KIP cover state: %u\n", state);
 		return "<unknown>";
 	}
 }

 static bool ssam_kip_cover_state_is_tablet_mode(struct ssam_tablet_sw *sw, u32 state)
 {
 	switch (state) {
 	case SSAM_KIP_COVER_STATE_DISCONNECTED:
 	case SSAM_KIP_COVER_STATE_FOLDED_CANVAS:
 	case SSAM_KIP_COVER_STATE_FOLDED_BACK:
 		return true;

 	case SSAM_KIP_COVER_STATE_CLOSED:
 	case SSAM_KIP_COVER_STATE_LAPTOP:
 		return false;

 	default:
 		dev_warn(&sw->sdev->dev, "unknown KIP cover state: %d\n", sw->state);
 		return true;
 	}
 }

 SSAM_DEFINE_SYNC_REQUEST_R(__ssam_kip_get_cover_state, u8, {
 	.target_category = SSAM_SSH_TC_KIP,
 	.target_id       = SSAM_SSH_TID_SAM,
 	.command_id      = 0x1d,
 	.instance_id     = 0x00,
 });

 static int ssam_kip_get_cover_state(struct ssam_tablet_sw *sw, u32 *state)
 {
 	int status;
 	u8 raw;

 	status = ssam_retry(__ssam_kip_get_cover_state, sw->sdev->ctrl, &raw);
 	if (status < 0) {
 		dev_err(&sw->sdev->dev, "failed to query KIP lid state: %d\n", status);
 		return status;
 	}

 	*state = raw;
 	return 0;
 }

 static u32 ssam_kip_sw_notif(struct ssam_event_notifier *nf, const struct ssam_event *event)
 {
 	struct ssam_tablet_sw *sw = container_of(nf, struct ssam_tablet_sw, notif);

 	if (event->command_id != SSAM_EVENT_KIP_CID_COVER_STATE_CHANGED)
 		return 0;	/* Return "unhandled". */

 	if (event->length < 1)
 		dev_warn(&sw->sdev->dev, "unexpected payload size: %u\n", event->length);

 	schedule_work(&sw->update_work);
 	return SSAM_NOTIF_HANDLED;
 }

 static const struct ssam_tablet_sw_desc ssam_kip_sw_desc = {
 	.dev = {
 		.name = "Microsoft Surface KIP Tablet Mode Switch",
 		.phys = "ssam/01:0e:01:00:01/input0",
 	},
 	.ops = {
 		.notify = ssam_kip_sw_notif,
 		.get_state = ssam_kip_get_cover_state,
 		.state_name = ssam_kip_cover_state_name,
 		.state_is_tablet_mode = ssam_kip_cover_state_is_tablet_mode,
 	},
 	.event = {
 		.reg = SSAM_EVENT_REGISTRY_SAM,
 		.id = {
 			.target_category = SSAM_SSH_TC_KIP,
 			.instance = 0,
 		},
 		.mask = SSAM_EVENT_MASK_TARGET,
 	},
 };


 /* -- SSAM POS tablet switch implementation. -------------------------------- */

 static bool tablet_mode_in_slate_state = true;
 module_param(tablet_mode_in_slate_state, bool, 0644);
 MODULE_PARM_DESC(tablet_mode_in_slate_state, "Enable tablet mode in slate device posture, default is 'true'");

 #define SSAM_EVENT_POS_CID_POSTURE_CHANGED	0x03
 #define SSAM_POS_MAX_SOURCES			4

 enum ssam_pos_state {
 	SSAM_POS_POSTURE_LID_CLOSED = 0x00,
 	SSAM_POS_POSTURE_LAPTOP     = 0x01,
 	SSAM_POS_POSTURE_SLATE      = 0x02,
 	SSAM_POS_POSTURE_TABLET     = 0x03,
 };

 struct ssam_sources_list {
 	__le32 count;
 	__le32 id[SSAM_POS_MAX_SOURCES];
 } __packed;

 static const char *ssam_pos_state_name(struct ssam_tablet_sw *sw, u32 state)
 {
 	switch (state) {
 	case SSAM_POS_POSTURE_LID_CLOSED:
 		return "closed";

 	case SSAM_POS_POSTURE_LAPTOP:
 		return "laptop";

 	case SSAM_POS_POSTURE_SLATE:
 		return "slate";

 	case SSAM_POS_POSTURE_TABLET:
 		return "tablet";

 	default:
 		dev_warn(&sw->sdev->dev, "unknown device posture: %u\n", state);
 		return "<unknown>";
 	}
 }

 static bool ssam_pos_state_is_tablet_mode(struct ssam_tablet_sw *sw, u32 state)
 {
 	switch (state) {
 	case SSAM_POS_POSTURE_LAPTOP:
 	case SSAM_POS_POSTURE_LID_CLOSED:
 		return false;

 	case SSAM_POS_POSTURE_SLATE:
 		return tablet_mode_in_slate_state;

 	case SSAM_POS_POSTURE_TABLET:
 		return true;

 	default:
 		dev_warn(&sw->sdev->dev, "unknown device posture: %u\n", state);
 		return true;
 	}
 }

 static int ssam_pos_get_sources_list(struct ssam_tablet_sw *sw, struct ssam_sources_list *sources)
 {
 	struct ssam_request rqst;
 	struct ssam_response rsp;
 	int status;

 	rqst.target_category = SSAM_SSH_TC_POS;
 	rqst.target_id = SSAM_SSH_TID_SAM;
 	rqst.command_id = 0x01;
 	rqst.instance_id = 0x00;
 	rqst.flags = SSAM_REQUEST_HAS_RESPONSE;
 	rqst.length = 0;
 	rqst.payload = NULL;

 	rsp.capacity = sizeof(*sources);
 	rsp.length = 0;
 	rsp.pointer = (u8 *)sources;

 	status = ssam_retry(ssam_request_do_sync_onstack, sw->sdev->ctrl, &rqst, &rsp, 0);
 	if (status)
 		return status;

 	/* We need at least the 'sources->count' field. */
 	if (rsp.length < sizeof(__le32)) {
 		dev_err(&sw->sdev->dev, "received source list response is too small\n");
 		return -EPROTO;
 	}

 	/* Make sure 'sources->count' matches with the response length. */
 	if (get_unaligned_le32(&sources->count) * sizeof(__le32) + sizeof(__le32) != rsp.length) {
 		dev_err(&sw->sdev->dev, "mismatch between number of sources and response size\n");
 		return -EPROTO;
 	}

 	return 0;
 }

 static int ssam_pos_get_source(struct ssam_tablet_sw *sw, u32 *source_id)
 {
 	struct ssam_sources_list sources = {};
 	int status;

 	status = ssam_pos_get_sources_list(sw, &sources);
 	if (status)
 		return status;

 	if (get_unaligned_le32(&sources.count) == 0) {
 		dev_err(&sw->sdev->dev, "no posture sources found\n");
 		return -ENODEV;
 	}

 	/*
 	 * We currently don't know what to do with more than one posture
 	 * source. At the moment, only one source seems to be used/provided.
 	 * The WARN_ON() here should hopefully let us know quickly once there
 	 * is a device that provides multiple sources, at which point we can
 	 * then try to figure out how to handle them.
 	 */
 	WARN_ON(get_unaligned_le32(&sources.count) > 1);

 	*source_id = get_unaligned_le32(&sources.id[0]);
 	return 0;
 }

 SSAM_DEFINE_SYNC_REQUEST_WR(__ssam_pos_get_posture_for_source, __le32, __le32, {
 	.target_category = SSAM_SSH_TC_POS,
 	.target_id       = SSAM_SSH_TID_SAM,
 	.command_id      = 0x02,
 	.instance_id     = 0x00,
 });

 static int ssam_pos_get_posture_for_source(struct ssam_tablet_sw *sw, u32 source_id, u32 *posture)
 {
 	__le32 source_le = cpu_to_le32(source_id);
 	__le32 rspval_le = 0;
 	int status;

 	status = ssam_retry(__ssam_pos_get_posture_for_source, sw->sdev->ctrl,
 			    &source_le, &rspval_le);
 	if (status)
 		return status;

 	*posture = le32_to_cpu(rspval_le);
 	return 0;
 }

 static int ssam_pos_get_posture(struct ssam_tablet_sw *sw, u32 *state)
 {
 	u32 source_id;
 	int status;

 	status = ssam_pos_get_source(sw, &source_id);
 	if (status) {
 		dev_err(&sw->sdev->dev, "failed to get posture source ID: %d\n", status);
 		return status;
 	}

 	status = ssam_pos_get_posture_for_source(sw, source_id, state);
 	if (status) {
 		dev_err(&sw->sdev->dev, "failed to get posture value for source %u: %d\n",
 			source_id, status);
 		return status;
 	}

 	return 0;
 }

 static u32 ssam_pos_sw_notif(struct ssam_event_notifier *nf, const struct ssam_event *event)
 {
 	struct ssam_tablet_sw *sw = container_of(nf, struct ssam_tablet_sw, notif);

 	if (event->command_id != SSAM_EVENT_POS_CID_POSTURE_CHANGED)
 		return 0;	/* Return "unhandled". */

 	if (event->length != sizeof(__le32) * 3)
 		dev_warn(&sw->sdev->dev, "unexpected payload size: %u\n", event->length);

 	schedule_work(&sw->update_work);
 	return SSAM_NOTIF_HANDLED;
 }

 static const struct ssam_tablet_sw_desc ssam_pos_sw_desc = {
 	.dev = {
 		.name = "Microsoft Surface POS Tablet Mode Switch",
 		.phys = "ssam/01:26:01:00:01/input0",
 	},
 	.ops = {
 		.notify = ssam_pos_sw_notif,
 		.get_state = ssam_pos_get_posture,
 		.state_name = ssam_pos_state_name,
 		.state_is_tablet_mode = ssam_pos_state_is_tablet_mode,
 	},
 	.event = {
 		.reg = SSAM_EVENT_REGISTRY_SAM,
 		.id = {
 			.target_category = SSAM_SSH_TC_POS,
 			.instance = 0,
 		},
 		.mask = SSAM_EVENT_MASK_TARGET,
 	},
 };


 /* -- Driver registration. -------------------------------------------------- */

 static const struct ssam_device_id ssam_tablet_sw_match[] = {
 	{ SSAM_SDEV(KIP, SAM, 0x00, 0x01), (unsigned long)&ssam_kip_sw_desc },
 	{ SSAM_SDEV(POS, SAM, 0x00, 0x01), (unsigned long)&ssam_pos_sw_desc },
 	{ },
 };
 MODULE_DEVICE_TABLE(ssam, ssam_tablet_sw_match);

 static struct ssam_device_driver ssam_tablet_sw_driver = {
 	.probe = ssam_tablet_sw_probe,
 	.remove = ssam_tablet_sw_remove,
 	.match_table = ssam_tablet_sw_match,
 	.driver = {
 		.name = "surface_aggregator_tablet_mode_switch",
 		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
 		.pm = &ssam_tablet_sw_pm_ops,
 	},
 };
 module_ssam_device_driver(ssam_tablet_sw_driver);

 MODULE_AUTHOR("Maximilian Luz <luzmaximilian@gmail.com>");
 MODULE_DESCRIPTION("Tablet mode switch driver for Surface devices using the Surface Aggregator Module");
 MODULE_LICENSE("GPL");
	// SPDX-License-Identifier: GPL-2.0+
	/*
	* Surface System Aggregator Module (SSAM) tablet mode switch driver.
	*
	* Copyright (C) 2022 Maximilian Luz <luzmaximilian@gmail.com>
	*/

	#include <asm/unaligned.h>
	#include <linux/input.h>
	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/types.h>
	#include <linux/workqueue.h>

	#include <linux/surface_aggregator/controller.h>
	#include <linux/surface_aggregator/device.h>


	/* -- SSAM generic tablet switch driver framework. -------------------------- */

	struct ssam_tablet_sw;

	struct ssam_tablet_sw_ops {
	int (get_state)(struct ssam_tablet_sw sw, u32 *state);
	const char (state_name)(struct ssam_tablet_sw *sw, u32 state);
	bool (state_is_tablet_mode)(struct ssam_tablet_sw sw, u32 state);
	};

	struct ssam_tablet_sw {
	struct ssam_device *sdev;

	u32 state;
	struct work_struct update_work;
	struct input_dev *mode_switch;

	struct ssam_tablet_sw_ops ops;
	struct ssam_event_notifier notif;
	};

	struct ssam_tablet_sw_desc {
	struct {
	const char *name;
	const char *phys;
	} dev;

	struct {
	u32 (notify)(struct ssam_event_notifier nf, const struct ssam_event *event);
	int (get_state)(struct ssam_tablet_sw sw, u32 *state);
	const char (state_name)(struct ssam_tablet_sw *sw, u32 state);
	bool (state_is_tablet_mode)(struct ssam_tablet_sw sw, u32 state);
	} ops;

	struct {
	struct ssam_event_registry reg;
	struct ssam_event_id id;
	enum ssam_event_mask mask;
	u8 flags;
	} event;
	};

	static ssize_t state_show(struct device dev, struct device_attribute attr, char *buf)
	{
	struct ssam_tablet_sw *sw = dev_get_drvdata(dev);
	const char *state = sw->ops.state_name(sw, sw->state);

	return sysfs_emit(buf, "%s\n", state);
	}
	static DEVICE_ATTR_RO(state);

	static struct attribute *ssam_tablet_sw_attrs[] = {
	&dev_attr_state.attr,
	NULL,
	};

	static const struct attribute_group ssam_tablet_sw_group = {
	.attrs = ssam_tablet_sw_attrs,
	};

	static void ssam_tablet_sw_update_workfn(struct work_struct *work)
	{
	struct ssam_tablet_sw *sw = container_of(work, struct ssam_tablet_sw, update_work);
	int tablet, status;
	u32 state;

	status = sw->ops.get_state(sw, &state);
	if (status)
	return;

	if (sw->state == state)
	return;
	sw->state = state;

	/* Send SW_TABLET_MODE event. */
	tablet = sw->ops.state_is_tablet_mode(sw, state);
	input_report_switch(sw->mode_switch, SW_TABLET_MODE, tablet);
	input_sync(sw->mode_switch);
	}

	static int __maybe_unused ssam_tablet_sw_resume(struct device *dev)
	{
	struct ssam_tablet_sw *sw = dev_get_drvdata(dev);

	schedule_work(&sw->update_work);
	return 0;
	}
	static SIMPLE_DEV_PM_OPS(ssam_tablet_sw_pm_ops, NULL, ssam_tablet_sw_resume);

	static int ssam_tablet_sw_probe(struct ssam_device *sdev)
	{
	const struct ssam_tablet_sw_desc *desc;
	struct ssam_tablet_sw *sw;
	int tablet, status;

	desc = ssam_device_get_match_data(sdev);
	if (!desc) {
	WARN(1, "no driver match data specified");
	return -EINVAL;
	}

	sw = devm_kzalloc(&sdev->dev, sizeof(*sw), GFP_KERNEL);
	if (!sw)
	return -ENOMEM;

	sw->sdev = sdev;

	sw->ops.get_state = desc->ops.get_state;
	sw->ops.state_name = desc->ops.state_name;
	sw->ops.state_is_tablet_mode = desc->ops.state_is_tablet_mode;

	INIT_WORK(&sw->update_work, ssam_tablet_sw_update_workfn);

	ssam_device_set_drvdata(sdev, sw);

	/* Get initial state. */
	status = sw->ops.get_state(sw, &sw->state);
	if (status)
	return status;

	/* Set up tablet mode switch. */
	sw->mode_switch = devm_input_allocate_device(&sdev->dev);
	if (!sw->mode_switch)
	return -ENOMEM;

	sw->mode_switch->name = desc->dev.name;
	sw->mode_switch->phys = desc->dev.phys;
	sw->mode_switch->id.bustype = BUS_HOST;
	sw->mode_switch->dev.parent = &sdev->dev;

	tablet = sw->ops.state_is_tablet_mode(sw, sw->state);
	input_set_capability(sw->mode_switch, EV_SW, SW_TABLET_MODE);
	input_report_switch(sw->mode_switch, SW_TABLET_MODE, tablet);

	status = input_register_device(sw->mode_switch);
	if (status)
	return status;

	/* Set up notifier. */
	sw->notif.base.priority = 0;
	sw->notif.base.fn = desc->ops.notify;
	sw->notif.event.reg = desc->event.reg;
	sw->notif.event.id = desc->event.id;
	sw->notif.event.mask = desc->event.mask;
	sw->notif.event.flags = SSAM_EVENT_SEQUENCED;

	status = ssam_device_notifier_register(sdev, &sw->notif);
	if (status)
	return status;

	status = sysfs_create_group(&sdev->dev.kobj, &ssam_tablet_sw_group);
	if (status)
	goto err;

	/* We might have missed events during setup, so check again. */
	schedule_work(&sw->update_work);
	return 0;

	err:
	ssam_device_notifier_unregister(sdev, &sw->notif);
	cancel_work_sync(&sw->update_work);
	return status;
	}

	static void ssam_tablet_sw_remove(struct ssam_device *sdev)
	{
	struct ssam_tablet_sw *sw = ssam_device_get_drvdata(sdev);

	sysfs_remove_group(&sdev->dev.kobj, &ssam_tablet_sw_group);

	ssam_device_notifier_unregister(sdev, &sw->notif);
	cancel_work_sync(&sw->update_work);
	}


	/* -- SSAM KIP tablet switch implementation. -------------------------------- */

	#define SSAM_EVENT_KIP_CID_COVER_STATE_CHANGED 0x1d

	enum ssam_kip_cover_state {
	SSAM_KIP_COVER_STATE_DISCONNECTED = 0x01,
	SSAM_KIP_COVER_STATE_CLOSED = 0x02,
	SSAM_KIP_COVER_STATE_LAPTOP = 0x03,
	SSAM_KIP_COVER_STATE_FOLDED_CANVAS = 0x04,
	SSAM_KIP_COVER_STATE_FOLDED_BACK = 0x05,
	};

	static const char ssam_kip_cover_state_name(struct ssam_tablet_sw sw, u32 state)
	{
	switch (state) {
	case SSAM_KIP_COVER_STATE_DISCONNECTED:
	return "disconnected";

	case SSAM_KIP_COVER_STATE_CLOSED:
	return "closed";

	case SSAM_KIP_COVER_STATE_LAPTOP:
	return "laptop";

	case SSAM_KIP_COVER_STATE_FOLDED_CANVAS:
	return "folded-canvas";

	case SSAM_KIP_COVER_STATE_FOLDED_BACK:
	return "folded-back";

	default:
	dev_warn(&sw->sdev->dev, "unknown KIP cover state: %u\n", state);
	return "<unknown>";
	}
	}

	static bool ssam_kip_cover_state_is_tablet_mode(struct ssam_tablet_sw *sw, u32 state)
	{
	switch (state) {
	case SSAM_KIP_COVER_STATE_DISCONNECTED:
	case SSAM_KIP_COVER_STATE_FOLDED_CANVAS:
	case SSAM_KIP_COVER_STATE_FOLDED_BACK:
	return true;

	case SSAM_KIP_COVER_STATE_CLOSED:
	case SSAM_KIP_COVER_STATE_LAPTOP:
	return false;

	default:
	dev_warn(&sw->sdev->dev, "unknown KIP cover state: %d\n", sw->state);
	return true;
	}
	}

	SSAM_DEFINE_SYNC_REQUEST_R(__ssam_kip_get_cover_state, u8, {
	.target_category = SSAM_SSH_TC_KIP,
	.target_id = SSAM_SSH_TID_SAM,
	.command_id = 0x1d,
	.instance_id = 0x00,
	});

	static int ssam_kip_get_cover_state(struct ssam_tablet_sw sw, u32 state)
	{
	int status;
	u8 raw;

	status = ssam_retry(__ssam_kip_get_cover_state, sw->sdev->ctrl, &raw);
	if (status < 0) {
	dev_err(&sw->sdev->dev, "failed to query KIP lid state: %d\n", status);
	return status;
	}

	*state = raw;
	return 0;
	}

	static u32 ssam_kip_sw_notif(struct ssam_event_notifier nf, const struct ssam_event event)
	{
	struct ssam_tablet_sw *sw = container_of(nf, struct ssam_tablet_sw, notif);

	if (event->command_id != SSAM_EVENT_KIP_CID_COVER_STATE_CHANGED)
	return 0; /* Return "unhandled". */

	if (event->length < 1)
	dev_warn(&sw->sdev->dev, "unexpected payload size: %u\n", event->length);

	schedule_work(&sw->update_work);
	return SSAM_NOTIF_HANDLED;
	}

	static const struct ssam_tablet_sw_desc ssam_kip_sw_desc = {
	.dev = {
	.name = "Microsoft Surface KIP Tablet Mode Switch",
	.phys = "ssam/01:0e:01:00:01/input0",
	},
	.ops = {
	.notify = ssam_kip_sw_notif,
	.get_state = ssam_kip_get_cover_state,
	.state_name = ssam_kip_cover_state_name,
	.state_is_tablet_mode = ssam_kip_cover_state_is_tablet_mode,
	},
	.event = {
	.reg = SSAM_EVENT_REGISTRY_SAM,
	.id = {
	.target_category = SSAM_SSH_TC_KIP,
	.instance = 0,
	},
	.mask = SSAM_EVENT_MASK_TARGET,
	},
	};


	/* -- SSAM POS tablet switch implementation. -------------------------------- */

	static bool tablet_mode_in_slate_state = true;
	module_param(tablet_mode_in_slate_state, bool, 0644);
	MODULE_PARM_DESC(tablet_mode_in_slate_state, "Enable tablet mode in slate device posture, default is 'true'");

	#define SSAM_EVENT_POS_CID_POSTURE_CHANGED 0x03
	#define SSAM_POS_MAX_SOURCES 4

	enum ssam_pos_state {
	SSAM_POS_POSTURE_LID_CLOSED = 0x00,
	SSAM_POS_POSTURE_LAPTOP = 0x01,
	SSAM_POS_POSTURE_SLATE = 0x02,
	SSAM_POS_POSTURE_TABLET = 0x03,
	};

	struct ssam_sources_list {
	__le32 count;
	__le32 id[SSAM_POS_MAX_SOURCES];
	} __packed;

	static const char ssam_pos_state_name(struct ssam_tablet_sw sw, u32 state)
	{
	switch (state) {
	case SSAM_POS_POSTURE_LID_CLOSED:
	return "closed";

	case SSAM_POS_POSTURE_LAPTOP:
	return "laptop";

	case SSAM_POS_POSTURE_SLATE:
	return "slate";

	case SSAM_POS_POSTURE_TABLET:
	return "tablet";

	default:
	dev_warn(&sw->sdev->dev, "unknown device posture: %u\n", state);
	return "<unknown>";
	}
	}

	static bool ssam_pos_state_is_tablet_mode(struct ssam_tablet_sw *sw, u32 state)
	{
	switch (state) {
	case SSAM_POS_POSTURE_LAPTOP:
	case SSAM_POS_POSTURE_LID_CLOSED:
	return false;

	case SSAM_POS_POSTURE_SLATE:
	return tablet_mode_in_slate_state;

	case SSAM_POS_POSTURE_TABLET:
	return true;

	default:
	dev_warn(&sw->sdev->dev, "unknown device posture: %u\n", state);
	return true;
	}
	}

	static int ssam_pos_get_sources_list(struct ssam_tablet_sw sw, struct ssam_sources_list sources)
	{
	struct ssam_request rqst;
	struct ssam_response rsp;
	int status;

	rqst.target_category = SSAM_SSH_TC_POS;
	rqst.target_id = SSAM_SSH_TID_SAM;
	rqst.command_id = 0x01;
	rqst.instance_id = 0x00;
	rqst.flags = SSAM_REQUEST_HAS_RESPONSE;
	rqst.length = 0;
	rqst.payload = NULL;

	rsp.capacity = sizeof(*sources);
	rsp.length = 0;
	rsp.pointer = (u8 *)sources;

	status = ssam_retry(ssam_request_do_sync_onstack, sw->sdev->ctrl, &rqst, &rsp, 0);
	if (status)
	return status;

	/* We need at least the 'sources->count' field. */
	if (rsp.length < sizeof(__le32)) {
	dev_err(&sw->sdev->dev, "received source list response is too small\n");
	return -EPROTO;
	}

	/* Make sure 'sources->count' matches with the response length. */
	if (get_unaligned_le32(&sources->count) * sizeof(__le32) + sizeof(__le32) != rsp.length) {
	dev_err(&sw->sdev->dev, "mismatch between number of sources and response size\n");
	return -EPROTO;
	}

	return 0;
	}

	static int ssam_pos_get_source(struct ssam_tablet_sw sw, u32 source_id)
	{
	struct ssam_sources_list sources = {};
	int status;

	status = ssam_pos_get_sources_list(sw, &sources);
	if (status)
	return status;

	if (get_unaligned_le32(&sources.count) == 0) {
	dev_err(&sw->sdev->dev, "no posture sources found\n");
	return -ENODEV;
	}

	/*
	* We currently don't know what to do with more than one posture
	* source. At the moment, only one source seems to be used/provided.
	* The WARN_ON() here should hopefully let us know quickly once there
	* is a device that provides multiple sources, at which point we can
	* then try to figure out how to handle them.
	*/
	WARN_ON(get_unaligned_le32(&sources.count) > 1);

	*source_id = get_unaligned_le32(&sources.id[0]);
	return 0;
	}

	SSAM_DEFINE_SYNC_REQUEST_WR(__ssam_pos_get_posture_for_source, __le32, __le32, {
	.target_category = SSAM_SSH_TC_POS,
	.target_id = SSAM_SSH_TID_SAM,
	.command_id = 0x02,
	.instance_id = 0x00,
	});

	static int ssam_pos_get_posture_for_source(struct ssam_tablet_sw sw, u32 source_id, u32 posture)
	{
	__le32 source_le = cpu_to_le32(source_id);
	__le32 rspval_le = 0;
	int status;

	status = ssam_retry(__ssam_pos_get_posture_for_source, sw->sdev->ctrl,
	&source_le, &rspval_le);
	if (status)
	return status;

	*posture = le32_to_cpu(rspval_le);
	return 0;
	}

	static int ssam_pos_get_posture(struct ssam_tablet_sw sw, u32 state)
	{
	u32 source_id;
	int status;

	status = ssam_pos_get_source(sw, &source_id);
	if (status) {
	dev_err(&sw->sdev->dev, "failed to get posture source ID: %d\n", status);
	return status;
	}

	status = ssam_pos_get_posture_for_source(sw, source_id, state);
	if (status) {
	dev_err(&sw->sdev->dev, "failed to get posture value for source %u: %d\n",
	source_id, status);
	return status;
	}

	return 0;
	}

	static u32 ssam_pos_sw_notif(struct ssam_event_notifier nf, const struct ssam_event event)
	{
	struct ssam_tablet_sw *sw = container_of(nf, struct ssam_tablet_sw, notif);

	if (event->command_id != SSAM_EVENT_POS_CID_POSTURE_CHANGED)
	return 0; /* Return "unhandled". */

	if (event->length != sizeof(__le32) * 3)
	dev_warn(&sw->sdev->dev, "unexpected payload size: %u\n", event->length);

	schedule_work(&sw->update_work);
	return SSAM_NOTIF_HANDLED;
	}

	static const struct ssam_tablet_sw_desc ssam_pos_sw_desc = {
	.dev = {
	.name = "Microsoft Surface POS Tablet Mode Switch",
	.phys = "ssam/01:26:01:00:01/input0",
	},
	.ops = {
	.notify = ssam_pos_sw_notif,
	.get_state = ssam_pos_get_posture,
	.state_name = ssam_pos_state_name,
	.state_is_tablet_mode = ssam_pos_state_is_tablet_mode,
	},
	.event = {
	.reg = SSAM_EVENT_REGISTRY_SAM,
	.id = {
	.target_category = SSAM_SSH_TC_POS,
	.instance = 0,
	},
	.mask = SSAM_EVENT_MASK_TARGET,
	},
	};


	/* -- Driver registration. -------------------------------------------------- */

	static const struct ssam_device_id ssam_tablet_sw_match[] = {
	{ SSAM_SDEV(KIP, SAM, 0x00, 0x01), (unsigned long)&ssam_kip_sw_desc },
	{ SSAM_SDEV(POS, SAM, 0x00, 0x01), (unsigned long)&ssam_pos_sw_desc },
	{ },
	};
	MODULE_DEVICE_TABLE(ssam, ssam_tablet_sw_match);

	static struct ssam_device_driver ssam_tablet_sw_driver = {
	.probe = ssam_tablet_sw_probe,
	.remove = ssam_tablet_sw_remove,
	.match_table = ssam_tablet_sw_match,
	.driver = {
	.name = "surface_aggregator_tablet_mode_switch",
	.probe_type = PROBE_PREFER_ASYNCHRONOUS,
	.pm = &ssam_tablet_sw_pm_ops,
	},
	};
	module_ssam_device_driver(ssam_tablet_sw_driver);

	MODULE_AUTHOR("Maximilian Luz <luzmaximilian@gmail.com>");
	MODULE_DESCRIPTION("Tablet mode switch driver for Surface devices using the Surface Aggregator Module");
	MODULE_LICENSE("GPL");