Adding upstream version 6.1.76.upstream/6.1.76upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1284 insertions, 0 deletions

diff --git a/drivers/platform/surface/surface_dtx.c b/drivers/platform/surface/surface_dtx.c
new file mode 100644
index 000000000..ed3694446
--- /dev/null
+++ b/drivers/platform/surface/surface_dtx.c
@@ -0,0 +1,1284 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Surface Book (gen. 2 and later) detachment system (DTX) driver.
+ *
+ * Provides a user-space interface to properly handle clipboard/tablet
+ * (containing screen and processor) detachment from the base of the device
+ * (containing the keyboard and optionally a discrete GPU). Allows to
+ * acknowledge (to speed things up), abort (e.g. in case the dGPU is still in
+ * use), or request detachment via user-space.
+ *
+ * Copyright (C) 2019-2022 Maximilian Luz <luzmaximilian@gmail.com>
+ */
+
+#include <linux/fs.h>
+#include <linux/input.h>
+#include <linux/ioctl.h>
+#include <linux/kernel.h>
+#include <linux/kfifo.h>
+#include <linux/kref.h>
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/platform_device.h>
+#include <linux/poll.h>
+#include <linux/rwsem.h>
+#include <linux/slab.h>
+#include <linux/workqueue.h>
+
+#include <linux/surface_aggregator/controller.h>
+#include <linux/surface_aggregator/device.h>
+#include <linux/surface_aggregator/dtx.h>
+
+
+/* -- SSAM interface. ------------------------------------------------------- */
+
+enum sam_event_cid_bas {
+	SAM_EVENT_CID_DTX_CONNECTION			= 0x0c,
+	SAM_EVENT_CID_DTX_REQUEST			= 0x0e,
+	SAM_EVENT_CID_DTX_CANCEL			= 0x0f,
+	SAM_EVENT_CID_DTX_LATCH_STATUS			= 0x11,
+};
+
+enum ssam_bas_base_state {
+	SSAM_BAS_BASE_STATE_DETACH_SUCCESS		= 0x00,
+	SSAM_BAS_BASE_STATE_ATTACHED			= 0x01,
+	SSAM_BAS_BASE_STATE_NOT_FEASIBLE		= 0x02,
+};
+
+enum ssam_bas_latch_status {
+	SSAM_BAS_LATCH_STATUS_CLOSED			= 0x00,
+	SSAM_BAS_LATCH_STATUS_OPENED			= 0x01,
+	SSAM_BAS_LATCH_STATUS_FAILED_TO_OPEN		= 0x02,
+	SSAM_BAS_LATCH_STATUS_FAILED_TO_REMAIN_OPEN	= 0x03,
+	SSAM_BAS_LATCH_STATUS_FAILED_TO_CLOSE		= 0x04,
+};
+
+enum ssam_bas_cancel_reason {
+	SSAM_BAS_CANCEL_REASON_NOT_FEASIBLE		= 0x00,  /* Low battery. */
+	SSAM_BAS_CANCEL_REASON_TIMEOUT			= 0x02,
+	SSAM_BAS_CANCEL_REASON_FAILED_TO_OPEN		= 0x03,
+	SSAM_BAS_CANCEL_REASON_FAILED_TO_REMAIN_OPEN	= 0x04,
+	SSAM_BAS_CANCEL_REASON_FAILED_TO_CLOSE		= 0x05,
+};
+
+struct ssam_bas_base_info {
+	u8 state;
+	u8 base_id;
+} __packed;
+
+static_assert(sizeof(struct ssam_bas_base_info) == 2);
+
+SSAM_DEFINE_SYNC_REQUEST_N(ssam_bas_latch_lock, {
+	.target_category = SSAM_SSH_TC_BAS,
+	.target_id       = 0x01,
+	.command_id      = 0x06,
+	.instance_id     = 0x00,
+});
+
+SSAM_DEFINE_SYNC_REQUEST_N(ssam_bas_latch_unlock, {
+	.target_category = SSAM_SSH_TC_BAS,
+	.target_id       = 0x01,
+	.command_id      = 0x07,
+	.instance_id     = 0x00,
+});
+
+SSAM_DEFINE_SYNC_REQUEST_N(ssam_bas_latch_request, {
+	.target_category = SSAM_SSH_TC_BAS,
+	.target_id       = 0x01,
+	.command_id      = 0x08,
+	.instance_id     = 0x00,
+});
+
+SSAM_DEFINE_SYNC_REQUEST_N(ssam_bas_latch_confirm, {
+	.target_category = SSAM_SSH_TC_BAS,
+	.target_id       = 0x01,
+	.command_id      = 0x09,
+	.instance_id     = 0x00,
+});
+
+SSAM_DEFINE_SYNC_REQUEST_N(ssam_bas_latch_heartbeat, {
+	.target_category = SSAM_SSH_TC_BAS,
+	.target_id       = 0x01,
+	.command_id      = 0x0a,
+	.instance_id     = 0x00,
+});
+
+SSAM_DEFINE_SYNC_REQUEST_N(ssam_bas_latch_cancel, {
+	.target_category = SSAM_SSH_TC_BAS,
+	.target_id       = 0x01,
+	.command_id      = 0x0b,
+	.instance_id     = 0x00,
+});
+
+SSAM_DEFINE_SYNC_REQUEST_R(ssam_bas_get_base, struct ssam_bas_base_info, {
+	.target_category = SSAM_SSH_TC_BAS,
+	.target_id       = 0x01,
+	.command_id      = 0x0c,
+	.instance_id     = 0x00,
+});
+
+SSAM_DEFINE_SYNC_REQUEST_R(ssam_bas_get_device_mode, u8, {
+	.target_category = SSAM_SSH_TC_BAS,
+	.target_id       = 0x01,
+	.command_id      = 0x0d,
+	.instance_id     = 0x00,
+});
+
+SSAM_DEFINE_SYNC_REQUEST_R(ssam_bas_get_latch_status, u8, {
+	.target_category = SSAM_SSH_TC_BAS,
+	.target_id       = 0x01,
+	.command_id      = 0x11,
+	.instance_id     = 0x00,
+});
+
+
+/* -- Main structures. ------------------------------------------------------ */
+
+enum sdtx_device_state {
+	SDTX_DEVICE_SHUTDOWN_BIT    = BIT(0),
+	SDTX_DEVICE_DIRTY_BASE_BIT  = BIT(1),
+	SDTX_DEVICE_DIRTY_MODE_BIT  = BIT(2),
+	SDTX_DEVICE_DIRTY_LATCH_BIT = BIT(3),
+};
+
+struct sdtx_device {
+	struct kref kref;
+	struct rw_semaphore lock;         /* Guards device and controller reference. */
+
+	struct device *dev;
+	struct ssam_controller *ctrl;
+	unsigned long flags;
+
+	struct miscdevice mdev;
+	wait_queue_head_t waitq;
+	struct mutex write_lock;          /* Guards order of events/notifications. */
+	struct rw_semaphore client_lock;  /* Guards client list.                   */
+	struct list_head client_list;
+
+	struct delayed_work state_work;
+	struct {
+		struct ssam_bas_base_info base;
+		u8 device_mode;
+		u8 latch_status;
+	} state;
+
+	struct delayed_work mode_work;
+	struct input_dev *mode_switch;
+
+	struct ssam_event_notifier notif;
+};
+
+enum sdtx_client_state {
+	SDTX_CLIENT_EVENTS_ENABLED_BIT = BIT(0),
+};
+
+struct sdtx_client {
+	struct sdtx_device *ddev;
+	struct list_head node;
+	unsigned long flags;
+
+	struct fasync_struct *fasync;
+
+	struct mutex read_lock;           /* Guards FIFO buffer read access. */
+	DECLARE_KFIFO(buffer, u8, 512);
+};
+
+static void __sdtx_device_release(struct kref *kref)
+{
+	struct sdtx_device *ddev = container_of(kref, struct sdtx_device, kref);
+
+	mutex_destroy(&ddev->write_lock);
+	kfree(ddev);
+}
+
+static struct sdtx_device *sdtx_device_get(struct sdtx_device *ddev)
+{
+	if (ddev)
+		kref_get(&ddev->kref);
+
+	return ddev;
+}
+
+static void sdtx_device_put(struct sdtx_device *ddev)
+{
+	if (ddev)
+		kref_put(&ddev->kref, __sdtx_device_release);
+}
+
+
+/* -- Firmware value translations. ------------------------------------------ */
+
+static u16 sdtx_translate_base_state(struct sdtx_device *ddev, u8 state)
+{
+	switch (state) {
+	case SSAM_BAS_BASE_STATE_ATTACHED:
+		return SDTX_BASE_ATTACHED;
+
+	case SSAM_BAS_BASE_STATE_DETACH_SUCCESS:
+		return SDTX_BASE_DETACHED;
+
+	case SSAM_BAS_BASE_STATE_NOT_FEASIBLE:
+		return SDTX_DETACH_NOT_FEASIBLE;
+
+	default:
+		dev_err(ddev->dev, "unknown base state: %#04x\n", state);
+		return SDTX_UNKNOWN(state);
+	}
+}
+
+static u16 sdtx_translate_latch_status(struct sdtx_device *ddev, u8 status)
+{
+	switch (status) {
+	case SSAM_BAS_LATCH_STATUS_CLOSED:
+		return SDTX_LATCH_CLOSED;
+
+	case SSAM_BAS_LATCH_STATUS_OPENED:
+		return SDTX_LATCH_OPENED;
+
+	case SSAM_BAS_LATCH_STATUS_FAILED_TO_OPEN:
+		return SDTX_ERR_FAILED_TO_OPEN;
+
+	case SSAM_BAS_LATCH_STATUS_FAILED_TO_REMAIN_OPEN:
+		return SDTX_ERR_FAILED_TO_REMAIN_OPEN;
+
+	case SSAM_BAS_LATCH_STATUS_FAILED_TO_CLOSE:
+		return SDTX_ERR_FAILED_TO_CLOSE;
+
+	default:
+		dev_err(ddev->dev, "unknown latch status: %#04x\n", status);
+		return SDTX_UNKNOWN(status);
+	}
+}
+
+static u16 sdtx_translate_cancel_reason(struct sdtx_device *ddev, u8 reason)
+{
+	switch (reason) {
+	case SSAM_BAS_CANCEL_REASON_NOT_FEASIBLE:
+		return SDTX_DETACH_NOT_FEASIBLE;
+
+	case SSAM_BAS_CANCEL_REASON_TIMEOUT:
+		return SDTX_DETACH_TIMEDOUT;
+
+	case SSAM_BAS_CANCEL_REASON_FAILED_TO_OPEN:
+		return SDTX_ERR_FAILED_TO_OPEN;
+
+	case SSAM_BAS_CANCEL_REASON_FAILED_TO_REMAIN_OPEN:
+		return SDTX_ERR_FAILED_TO_REMAIN_OPEN;
+
+	case SSAM_BAS_CANCEL_REASON_FAILED_TO_CLOSE:
+		return SDTX_ERR_FAILED_TO_CLOSE;
+
+	default:
+		dev_err(ddev->dev, "unknown cancel reason: %#04x\n", reason);
+		return SDTX_UNKNOWN(reason);
+	}
+}
+
+
+/* -- IOCTLs. --------------------------------------------------------------- */
+
+static int sdtx_ioctl_get_base_info(struct sdtx_device *ddev,
+				    struct sdtx_base_info __user *buf)
+{
+	struct ssam_bas_base_info raw;
+	struct sdtx_base_info info;
+	int status;
+
+	lockdep_assert_held_read(&ddev->lock);
+
+	status = ssam_retry(ssam_bas_get_base, ddev->ctrl, &raw);
+	if (status < 0)
+		return status;
+
+	info.state = sdtx_translate_base_state(ddev, raw.state);
+	info.base_id = SDTX_BASE_TYPE_SSH(raw.base_id);
+
+	if (copy_to_user(buf, &info, sizeof(info)))
+		return -EFAULT;
+
+	return 0;
+}
+
+static int sdtx_ioctl_get_device_mode(struct sdtx_device *ddev, u16 __user *buf)
+{
+	u8 mode;
+	int status;
+
+	lockdep_assert_held_read(&ddev->lock);
+
+	status = ssam_retry(ssam_bas_get_device_mode, ddev->ctrl, &mode);
+	if (status < 0)
+		return status;
+
+	return put_user(mode, buf);
+}
+
+static int sdtx_ioctl_get_latch_status(struct sdtx_device *ddev, u16 __user *buf)
+{
+	u8 latch;
+	int status;
+
+	lockdep_assert_held_read(&ddev->lock);
+
+	status = ssam_retry(ssam_bas_get_latch_status, ddev->ctrl, &latch);
+	if (status < 0)
+		return status;
+
+	return put_user(sdtx_translate_latch_status(ddev, latch), buf);
+}
+
+static long __surface_dtx_ioctl(struct sdtx_client *client, unsigned int cmd, unsigned long arg)
+{
+	struct sdtx_device *ddev = client->ddev;
+
+	lockdep_assert_held_read(&ddev->lock);
+
+	switch (cmd) {
+	case SDTX_IOCTL_EVENTS_ENABLE:
+		set_bit(SDTX_CLIENT_EVENTS_ENABLED_BIT, &client->flags);
+		return 0;
+
+	case SDTX_IOCTL_EVENTS_DISABLE:
+		clear_bit(SDTX_CLIENT_EVENTS_ENABLED_BIT, &client->flags);
+		return 0;
+
+	case SDTX_IOCTL_LATCH_LOCK:
+		return ssam_retry(ssam_bas_latch_lock, ddev->ctrl);
+
+	case SDTX_IOCTL_LATCH_UNLOCK:
+		return ssam_retry(ssam_bas_latch_unlock, ddev->ctrl);
+
+	case SDTX_IOCTL_LATCH_REQUEST:
+		return ssam_retry(ssam_bas_latch_request, ddev->ctrl);
+
+	case SDTX_IOCTL_LATCH_CONFIRM:
+		return ssam_retry(ssam_bas_latch_confirm, ddev->ctrl);
+
+	case SDTX_IOCTL_LATCH_HEARTBEAT:
+		return ssam_retry(ssam_bas_latch_heartbeat, ddev->ctrl);
+
+	case SDTX_IOCTL_LATCH_CANCEL:
+		return ssam_retry(ssam_bas_latch_cancel, ddev->ctrl);
+
+	case SDTX_IOCTL_GET_BASE_INFO:
+		return sdtx_ioctl_get_base_info(ddev, (struct sdtx_base_info __user *)arg);
+
+	case SDTX_IOCTL_GET_DEVICE_MODE:
+		return sdtx_ioctl_get_device_mode(ddev, (u16 __user *)arg);
+
+	case SDTX_IOCTL_GET_LATCH_STATUS:
+		return sdtx_ioctl_get_latch_status(ddev, (u16 __user *)arg);
+
+	default:
+		return -EINVAL;
+	}
+}
+
+static long surface_dtx_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+	struct sdtx_client *client = file->private_data;
+	long status;
+
+	if (down_read_killable(&client->ddev->lock))
+		return -ERESTARTSYS;
+
+	if (test_bit(SDTX_DEVICE_SHUTDOWN_BIT, &client->ddev->flags)) {
+		up_read(&client->ddev->lock);
+		return -ENODEV;
+	}
+
+	status = __surface_dtx_ioctl(client, cmd, arg);
+
+	up_read(&client->ddev->lock);
+	return status;
+}
+
+
+/* -- File operations. ------------------------------------------------------ */
+
+static int surface_dtx_open(struct inode *inode, struct file *file)
+{
+	struct sdtx_device *ddev = container_of(file->private_data, struct sdtx_device, mdev);
+	struct sdtx_client *client;
+
+	/* Initialize client. */
+	client = kzalloc(sizeof(*client), GFP_KERNEL);
+	if (!client)
+		return -ENOMEM;
+
+	client->ddev = sdtx_device_get(ddev);
+
+	INIT_LIST_HEAD(&client->node);
+
+	mutex_init(&client->read_lock);
+	INIT_KFIFO(client->buffer);
+
+	file->private_data = client;
+
+	/* Attach client. */
+	down_write(&ddev->client_lock);
+
+	/*
+	 * Do not add a new client if the device has been shut down. Note that
+	 * it's enough to hold the client_lock here as, during shutdown, we
+	 * only acquire that lock and remove clients after marking the device
+	 * as shut down.
+	 */
+	if (test_bit(SDTX_DEVICE_SHUTDOWN_BIT, &ddev->flags)) {
+		up_write(&ddev->client_lock);
+		mutex_destroy(&client->read_lock);
+		sdtx_device_put(client->ddev);
+		kfree(client);
+		return -ENODEV;
+	}
+
+	list_add_tail(&client->node, &ddev->client_list);
+	up_write(&ddev->client_lock);
+
+	stream_open(inode, file);
+	return 0;
+}
+
+static int surface_dtx_release(struct inode *inode, struct file *file)
+{
+	struct sdtx_client *client = file->private_data;
+
+	/* Detach client. */
+	down_write(&client->ddev->client_lock);
+	list_del(&client->node);
+	up_write(&client->ddev->client_lock);
+
+	/* Free client. */
+	sdtx_device_put(client->ddev);
+	mutex_destroy(&client->read_lock);
+	kfree(client);
+
+	return 0;
+}
+
+static ssize_t surface_dtx_read(struct file *file, char __user *buf, size_t count, loff_t *offs)
+{
+	struct sdtx_client *client = file->private_data;
+	struct sdtx_device *ddev = client->ddev;
+	unsigned int copied;
+	int status = 0;
+
+	if (down_read_killable(&ddev->lock))
+		return -ERESTARTSYS;
+
+	/* Make sure we're not shut down. */
+	if (test_bit(SDTX_DEVICE_SHUTDOWN_BIT, &ddev->flags)) {
+		up_read(&ddev->lock);
+		return -ENODEV;
+	}
+
+	do {
+		/* Check availability, wait if necessary. */
+		if (kfifo_is_empty(&client->buffer)) {
+			up_read(&ddev->lock);
+
+			if (file->f_flags & O_NONBLOCK)
+				return -EAGAIN;
+
+			status = wait_event_interruptible(ddev->waitq,
+							  !kfifo_is_empty(&client->buffer) ||
+							  test_bit(SDTX_DEVICE_SHUTDOWN_BIT,
+								   &ddev->flags));
+			if (status < 0)
+				return status;
+
+			if (down_read_killable(&ddev->lock))
+				return -ERESTARTSYS;
+
+			/* Need to check that we're not shut down again. */
+			if (test_bit(SDTX_DEVICE_SHUTDOWN_BIT, &ddev->flags)) {
+				up_read(&ddev->lock);
+				return -ENODEV;
+			}
+		}
+
+		/* Try to read from FIFO. */
+		if (mutex_lock_interruptible(&client->read_lock)) {
+			up_read(&ddev->lock);
+			return -ERESTARTSYS;
+		}
+
+		status = kfifo_to_user(&client->buffer, buf, count, &copied);
+		mutex_unlock(&client->read_lock);
+
+		if (status < 0) {
+			up_read(&ddev->lock);
+			return status;
+		}
+
+		/* We might not have gotten anything, check this here. */
+		if (copied == 0 && (file->f_flags & O_NONBLOCK)) {
+			up_read(&ddev->lock);
+			return -EAGAIN;
+		}
+	} while (copied == 0);
+
+	up_read(&ddev->lock);
+	return copied;
+}
+
+static __poll_t surface_dtx_poll(struct file *file, struct poll_table_struct *pt)
+{
+	struct sdtx_client *client = file->private_data;
+	__poll_t events = 0;
+
+	if (test_bit(SDTX_DEVICE_SHUTDOWN_BIT, &client->ddev->flags))
+		return EPOLLHUP | EPOLLERR;
+
+	poll_wait(file, &client->ddev->waitq, pt);
+
+	if (!kfifo_is_empty(&client->buffer))
+		events |= EPOLLIN | EPOLLRDNORM;
+
+	return events;
+}
+
+static int surface_dtx_fasync(int fd, struct file *file, int on)
+{
+	struct sdtx_client *client = file->private_data;
+
+	return fasync_helper(fd, file, on, &client->fasync);
+}
+
+static const struct file_operations surface_dtx_fops = {
+	.owner          = THIS_MODULE,
+	.open           = surface_dtx_open,
+	.release        = surface_dtx_release,
+	.read           = surface_dtx_read,
+	.poll           = surface_dtx_poll,
+	.fasync         = surface_dtx_fasync,
+	.unlocked_ioctl = surface_dtx_ioctl,
+	.compat_ioctl   = surface_dtx_ioctl,
+	.llseek         = no_llseek,
+};
+
+
+/* -- Event handling/forwarding. -------------------------------------------- */
+
+/*
+ * The device operation mode is not immediately updated on the EC when the
+ * base has been connected, i.e. querying the device mode inside the
+ * connection event callback yields an outdated value. Thus, we can only
+ * determine the new tablet-mode switch and device mode values after some
+ * time.
+ *
+ * These delays have been chosen by experimenting. We first delay on connect
+ * events, then check and validate the device mode against the base state and
+ * if invalid delay again by the "recheck" delay.
+ */
+#define SDTX_DEVICE_MODE_DELAY_CONNECT	msecs_to_jiffies(100)
+#define SDTX_DEVICE_MODE_DELAY_RECHECK	msecs_to_jiffies(100)
+
+struct sdtx_status_event {
+	struct sdtx_event e;
+	__u16 v;
+} __packed;
+
+struct sdtx_base_info_event {
+	struct sdtx_event e;
+	struct sdtx_base_info v;
+} __packed;
+
+union sdtx_generic_event {
+	struct sdtx_event common;
+	struct sdtx_status_event status;
+	struct sdtx_base_info_event base;
+};
+
+static void sdtx_update_device_mode(struct sdtx_device *ddev, unsigned long delay);
+
+/* Must be executed with ddev->write_lock held. */
+static void sdtx_push_event(struct sdtx_device *ddev, struct sdtx_event *evt)
+{
+	const size_t len = sizeof(struct sdtx_event) + evt->length;
+	struct sdtx_client *client;
+
+	lockdep_assert_held(&ddev->write_lock);
+
+	down_read(&ddev->client_lock);
+	list_for_each_entry(client, &ddev->client_list, node) {
+		if (!test_bit(SDTX_CLIENT_EVENTS_ENABLED_BIT, &client->flags))
+			continue;
+
+		if (likely(kfifo_avail(&client->buffer) >= len))
+			kfifo_in(&client->buffer, (const u8 *)evt, len);
+		else
+			dev_warn(ddev->dev, "event buffer overrun\n");
+
+		kill_fasync(&client->fasync, SIGIO, POLL_IN);
+	}
+	up_read(&ddev->client_lock);
+
+	wake_up_interruptible(&ddev->waitq);
+}
+
+static u32 sdtx_notifier(struct ssam_event_notifier *nf, const struct ssam_event *in)
+{
+	struct sdtx_device *ddev = container_of(nf, struct sdtx_device, notif);
+	union sdtx_generic_event event;
+	size_t len;
+
+	/* Validate event payload length. */
+	switch (in->command_id) {
+	case SAM_EVENT_CID_DTX_CONNECTION:
+		len = 2 * sizeof(u8);
+		break;
+
+	case SAM_EVENT_CID_DTX_REQUEST:
+		len = 0;
+		break;
+
+	case SAM_EVENT_CID_DTX_CANCEL:
+		len = sizeof(u8);
+		break;
+
+	case SAM_EVENT_CID_DTX_LATCH_STATUS:
+		len = sizeof(u8);
+		break;
+
+	default:
+		return 0;
+	}
+
+	if (in->length != len) {
+		dev_err(ddev->dev,
+			"unexpected payload size for event %#04x: got %u, expected %zu\n",
+			in->command_id, in->length, len);
+		return 0;
+	}
+
+	mutex_lock(&ddev->write_lock);
+
+	/* Translate event. */
+	switch (in->command_id) {
+	case SAM_EVENT_CID_DTX_CONNECTION:
+		clear_bit(SDTX_DEVICE_DIRTY_BASE_BIT, &ddev->flags);
+
+		/* If state has not changed: do not send new event. */
+		if (ddev->state.base.state == in->data[0] &&
+		    ddev->state.base.base_id == in->data[1])
+			goto out;
+
+		ddev->state.base.state = in->data[0];
+		ddev->state.base.base_id = in->data[1];
+
+		event.base.e.length = sizeof(struct sdtx_base_info);
+		event.base.e.code = SDTX_EVENT_BASE_CONNECTION;
+		event.base.v.state = sdtx_translate_base_state(ddev, in->data[0]);
+		event.base.v.base_id = SDTX_BASE_TYPE_SSH(in->data[1]);
+		break;
+
+	case SAM_EVENT_CID_DTX_REQUEST:
+		event.common.code = SDTX_EVENT_REQUEST;
+		event.common.length = 0;
+		break;
+
+	case SAM_EVENT_CID_DTX_CANCEL:
+		event.status.e.length = sizeof(u16);
+		event.status.e.code = SDTX_EVENT_CANCEL;
+		event.status.v = sdtx_translate_cancel_reason(ddev, in->data[0]);
+		break;
+
+	case SAM_EVENT_CID_DTX_LATCH_STATUS:
+		clear_bit(SDTX_DEVICE_DIRTY_LATCH_BIT, &ddev->flags);
+
+		/* If state has not changed: do not send new event. */
+		if (ddev->state.latch_status == in->data[0])
+			goto out;
+
+		ddev->state.latch_status = in->data[0];
+
+		event.status.e.length = sizeof(u16);
+		event.status.e.code = SDTX_EVENT_LATCH_STATUS;
+		event.status.v = sdtx_translate_latch_status(ddev, in->data[0]);
+		break;
+	}
+
+	sdtx_push_event(ddev, &event.common);
+
+	/* Update device mode on base connection change. */
+	if (in->command_id == SAM_EVENT_CID_DTX_CONNECTION) {
+		unsigned long delay;
+
+		delay = in->data[0] ? SDTX_DEVICE_MODE_DELAY_CONNECT : 0;
+		sdtx_update_device_mode(ddev, delay);
+	}
+
+out:
+	mutex_unlock(&ddev->write_lock);
+	return SSAM_NOTIF_HANDLED;
+}
+
+
+/* -- State update functions. ----------------------------------------------- */
+
+static bool sdtx_device_mode_invalid(u8 mode, u8 base_state)
+{
+	return ((base_state == SSAM_BAS_BASE_STATE_ATTACHED) &&
+		(mode == SDTX_DEVICE_MODE_TABLET)) ||
+	       ((base_state == SSAM_BAS_BASE_STATE_DETACH_SUCCESS) &&
+		(mode != SDTX_DEVICE_MODE_TABLET));
+}
+
+static void sdtx_device_mode_workfn(struct work_struct *work)
+{
+	struct sdtx_device *ddev = container_of(work, struct sdtx_device, mode_work.work);
+	struct sdtx_status_event event;
+	struct ssam_bas_base_info base;
+	int status, tablet;
+	u8 mode;
+
+	/* Get operation mode. */
+	status = ssam_retry(ssam_bas_get_device_mode, ddev->ctrl, &mode);
+	if (status) {
+		dev_err(ddev->dev, "failed to get device mode: %d\n", status);
+		return;
+	}
+
+	/* Get base info. */
+	status = ssam_retry(ssam_bas_get_base, ddev->ctrl, &base);
+	if (status) {
+		dev_err(ddev->dev, "failed to get base info: %d\n", status);
+		return;
+	}
+
+	/*
+	 * In some cases (specifically when attaching the base), the device
+	 * mode isn't updated right away. Thus we check if the device mode
+	 * makes sense for the given base state and try again later if it
+	 * doesn't.
+	 */
+	if (sdtx_device_mode_invalid(mode, base.state)) {
+		dev_dbg(ddev->dev, "device mode is invalid, trying again\n");
+		sdtx_update_device_mode(ddev, SDTX_DEVICE_MODE_DELAY_RECHECK);
+		return;
+	}
+
+	mutex_lock(&ddev->write_lock);
+	clear_bit(SDTX_DEVICE_DIRTY_MODE_BIT, &ddev->flags);
+
+	/* Avoid sending duplicate device-mode events. */
+	if (ddev->state.device_mode == mode) {
+		mutex_unlock(&ddev->write_lock);
+		return;
+	}
+
+	ddev->state.device_mode = mode;
+
+	event.e.length = sizeof(u16);
+	event.e.code = SDTX_EVENT_DEVICE_MODE;
+	event.v = mode;
+
+	sdtx_push_event(ddev, &event.e);
+
+	/* Send SW_TABLET_MODE event. */
+	tablet = mode != SDTX_DEVICE_MODE_LAPTOP;
+	input_report_switch(ddev->mode_switch, SW_TABLET_MODE, tablet);
+	input_sync(ddev->mode_switch);
+
+	mutex_unlock(&ddev->write_lock);
+}
+
+static void sdtx_update_device_mode(struct sdtx_device *ddev, unsigned long delay)
+{
+	schedule_delayed_work(&ddev->mode_work, delay);
+}
+
+/* Must be executed with ddev->write_lock held. */
+static void __sdtx_device_state_update_base(struct sdtx_device *ddev,
+					    struct ssam_bas_base_info info)
+{
+	struct sdtx_base_info_event event;
+
+	lockdep_assert_held(&ddev->write_lock);
+
+	/* Prevent duplicate events. */
+	if (ddev->state.base.state == info.state &&
+	    ddev->state.base.base_id == info.base_id)
+		return;
+
+	ddev->state.base = info;
+
+	event.e.length = sizeof(struct sdtx_base_info);
+	event.e.code = SDTX_EVENT_BASE_CONNECTION;
+	event.v.state = sdtx_translate_base_state(ddev, info.state);
+	event.v.base_id = SDTX_BASE_TYPE_SSH(info.base_id);
+
+	sdtx_push_event(ddev, &event.e);
+}
+
+/* Must be executed with ddev->write_lock held. */
+static void __sdtx_device_state_update_mode(struct sdtx_device *ddev, u8 mode)
+{
+	struct sdtx_status_event event;
+	int tablet;
+
+	/*
+	 * Note: This function must be called after updating the base state
+	 * via __sdtx_device_state_update_base(), as we rely on the updated
+	 * base state value in the validity check below.
+	 */
+
+	lockdep_assert_held(&ddev->write_lock);
+
+	if (sdtx_device_mode_invalid(mode, ddev->state.base.state)) {
+		dev_dbg(ddev->dev, "device mode is invalid, trying again\n");
+		sdtx_update_device_mode(ddev, SDTX_DEVICE_MODE_DELAY_RECHECK);
+		return;
+	}
+
+	/* Prevent duplicate events. */
+	if (ddev->state.device_mode == mode)
+		return;
+
+	ddev->state.device_mode = mode;
+
+	/* Send event. */
+	event.e.length = sizeof(u16);
+	event.e.code = SDTX_EVENT_DEVICE_MODE;
+	event.v = mode;
+
+	sdtx_push_event(ddev, &event.e);
+
+	/* Send SW_TABLET_MODE event. */
+	tablet = mode != SDTX_DEVICE_MODE_LAPTOP;
+	input_report_switch(ddev->mode_switch, SW_TABLET_MODE, tablet);
+	input_sync(ddev->mode_switch);
+}
+
+/* Must be executed with ddev->write_lock held. */
+static void __sdtx_device_state_update_latch(struct sdtx_device *ddev, u8 status)
+{
+	struct sdtx_status_event event;
+
+	lockdep_assert_held(&ddev->write_lock);
+
+	/* Prevent duplicate events. */
+	if (ddev->state.latch_status == status)
+		return;
+
+	ddev->state.latch_status = status;
+
+	event.e.length = sizeof(struct sdtx_base_info);
+	event.e.code = SDTX_EVENT_BASE_CONNECTION;
+	event.v = sdtx_translate_latch_status(ddev, status);
+
+	sdtx_push_event(ddev, &event.e);
+}
+
+static void sdtx_device_state_workfn(struct work_struct *work)
+{
+	struct sdtx_device *ddev = container_of(work, struct sdtx_device, state_work.work);
+	struct ssam_bas_base_info base;
+	u8 mode, latch;
+	int status;
+
+	/* Mark everything as dirty. */
+	set_bit(SDTX_DEVICE_DIRTY_BASE_BIT, &ddev->flags);
+	set_bit(SDTX_DEVICE_DIRTY_MODE_BIT, &ddev->flags);
+	set_bit(SDTX_DEVICE_DIRTY_LATCH_BIT, &ddev->flags);
+
+	/*
+	 * Ensure that the state gets marked as dirty before continuing to
+	 * query it. Necessary to ensure that clear_bit() calls in
+	 * sdtx_notifier() and sdtx_device_mode_workfn() actually clear these
+	 * bits if an event is received while updating the state here.
+	 */
+	smp_mb__after_atomic();
+
+	status = ssam_retry(ssam_bas_get_base, ddev->ctrl, &base);
+	if (status) {
+		dev_err(ddev->dev, "failed to get base state: %d\n", status);
+		return;
+	}
+
+	status = ssam_retry(ssam_bas_get_device_mode, ddev->ctrl, &mode);
+	if (status) {
+		dev_err(ddev->dev, "failed to get device mode: %d\n", status);
+		return;
+	}
+
+	status = ssam_retry(ssam_bas_get_latch_status, ddev->ctrl, &latch);
+	if (status) {
+		dev_err(ddev->dev, "failed to get latch status: %d\n", status);
+		return;
+	}
+
+	mutex_lock(&ddev->write_lock);
+
+	/*
+	 * If the respective dirty-bit has been cleared, an event has been
+	 * received, updating this state. The queried state may thus be out of
+	 * date. At this point, we can safely assume that the state provided
+	 * by the event is either up to date, or we're about to receive
+	 * another event updating it.
+	 */
+
+	if (test_and_clear_bit(SDTX_DEVICE_DIRTY_BASE_BIT, &ddev->flags))
+		__sdtx_device_state_update_base(ddev, base);
+
+	if (test_and_clear_bit(SDTX_DEVICE_DIRTY_MODE_BIT, &ddev->flags))
+		__sdtx_device_state_update_mode(ddev, mode);
+
+	if (test_and_clear_bit(SDTX_DEVICE_DIRTY_LATCH_BIT, &ddev->flags))
+		__sdtx_device_state_update_latch(ddev, latch);
+
+	mutex_unlock(&ddev->write_lock);
+}
+
+static void sdtx_update_device_state(struct sdtx_device *ddev, unsigned long delay)
+{
+	schedule_delayed_work(&ddev->state_work, delay);
+}
+
+
+/* -- Common device initialization. ----------------------------------------- */
+
+static int sdtx_device_init(struct sdtx_device *ddev, struct device *dev,
+			    struct ssam_controller *ctrl)
+{
+	int status, tablet_mode;
+
+	/* Basic initialization. */
+	kref_init(&ddev->kref);
+	init_rwsem(&ddev->lock);
+	ddev->dev = dev;
+	ddev->ctrl = ctrl;
+
+	ddev->mdev.minor = MISC_DYNAMIC_MINOR;
+	ddev->mdev.name = "surface_dtx";
+	ddev->mdev.nodename = "surface/dtx";
+	ddev->mdev.fops = &surface_dtx_fops;
+
+	ddev->notif.base.priority = 1;
+	ddev->notif.base.fn = sdtx_notifier;
+	ddev->notif.event.reg = SSAM_EVENT_REGISTRY_SAM;
+	ddev->notif.event.id.target_category = SSAM_SSH_TC_BAS;
+	ddev->notif.event.id.instance = 0;
+	ddev->notif.event.mask = SSAM_EVENT_MASK_NONE;
+	ddev->notif.event.flags = SSAM_EVENT_SEQUENCED;
+
+	init_waitqueue_head(&ddev->waitq);
+	mutex_init(&ddev->write_lock);
+	init_rwsem(&ddev->client_lock);
+	INIT_LIST_HEAD(&ddev->client_list);
+
+	INIT_DELAYED_WORK(&ddev->mode_work, sdtx_device_mode_workfn);
+	INIT_DELAYED_WORK(&ddev->state_work, sdtx_device_state_workfn);
+
+	/*
+	 * Get current device state. We want to guarantee that events are only
+	 * sent when state actually changes. Thus we cannot use special
+	 * "uninitialized" values, as that would cause problems when manually
+	 * querying the state in surface_dtx_pm_complete(). I.e. we would not
+	 * be able to detect state changes there if no change event has been
+	 * received between driver initialization and first device suspension.
+	 *
+	 * Note that we also need to do this before registering the event
+	 * notifier, as that may access the state values.
+	 */
+	status = ssam_retry(ssam_bas_get_base, ddev->ctrl, &ddev->state.base);
+	if (status)
+		return status;
+
+	status = ssam_retry(ssam_bas_get_device_mode, ddev->ctrl, &ddev->state.device_mode);
+	if (status)
+		return status;
+
+	status = ssam_retry(ssam_bas_get_latch_status, ddev->ctrl, &ddev->state.latch_status);
+	if (status)
+		return status;
+
+	/* Set up tablet mode switch. */
+	ddev->mode_switch = input_allocate_device();
+	if (!ddev->mode_switch)
+		return -ENOMEM;
+
+	ddev->mode_switch->name = "Microsoft Surface DTX Device Mode Switch";
+	ddev->mode_switch->phys = "ssam/01:11:01:00:00/input0";
+	ddev->mode_switch->id.bustype = BUS_HOST;
+	ddev->mode_switch->dev.parent = ddev->dev;
+
+	tablet_mode = (ddev->state.device_mode != SDTX_DEVICE_MODE_LAPTOP);
+	input_set_capability(ddev->mode_switch, EV_SW, SW_TABLET_MODE);
+	input_report_switch(ddev->mode_switch, SW_TABLET_MODE, tablet_mode);
+
+	status = input_register_device(ddev->mode_switch);
+	if (status) {
+		input_free_device(ddev->mode_switch);
+		return status;
+	}
+
+	/* Set up event notifier. */
+	status = ssam_notifier_register(ddev->ctrl, &ddev->notif);
+	if (status)
+		goto err_notif;
+
+	/* Register miscdevice. */
+	status = misc_register(&ddev->mdev);
+	if (status)
+		goto err_mdev;
+
+	/*
+	 * Update device state in case it has changed between getting the
+	 * initial mode and registering the event notifier.
+	 */
+	sdtx_update_device_state(ddev, 0);
+	return 0;
+
+err_notif:
+	ssam_notifier_unregister(ddev->ctrl, &ddev->notif);
+	cancel_delayed_work_sync(&ddev->mode_work);
+err_mdev:
+	input_unregister_device(ddev->mode_switch);
+	return status;
+}
+
+static struct sdtx_device *sdtx_device_create(struct device *dev, struct ssam_controller *ctrl)
+{
+	struct sdtx_device *ddev;
+	int status;
+
+	ddev = kzalloc(sizeof(*ddev), GFP_KERNEL);
+	if (!ddev)
+		return ERR_PTR(-ENOMEM);
+
+	status = sdtx_device_init(ddev, dev, ctrl);
+	if (status) {
+		sdtx_device_put(ddev);
+		return ERR_PTR(status);
+	}
+
+	return ddev;
+}
+
+static void sdtx_device_destroy(struct sdtx_device *ddev)
+{
+	struct sdtx_client *client;
+
+	/*
+	 * Mark device as shut-down. Prevent new clients from being added and
+	 * new operations from being executed.
+	 */
+	set_bit(SDTX_DEVICE_SHUTDOWN_BIT, &ddev->flags);
+
+	/* Disable notifiers, prevent new events from arriving. */
+	ssam_notifier_unregister(ddev->ctrl, &ddev->notif);
+
+	/* Stop mode_work, prevent access to mode_switch. */
+	cancel_delayed_work_sync(&ddev->mode_work);
+
+	/* Stop state_work. */
+	cancel_delayed_work_sync(&ddev->state_work);
+
+	/* With mode_work canceled, we can unregister the mode_switch. */
+	input_unregister_device(ddev->mode_switch);
+
+	/* Wake up async clients. */
+	down_write(&ddev->client_lock);
+	list_for_each_entry(client, &ddev->client_list, node) {
+		kill_fasync(&client->fasync, SIGIO, POLL_HUP);
+	}
+	up_write(&ddev->client_lock);
+
+	/* Wake up blocking clients. */
+	wake_up_interruptible(&ddev->waitq);
+
+	/*
+	 * Wait for clients to finish their current operation. After this, the
+	 * controller and device references are guaranteed to be no longer in
+	 * use.
+	 */
+	down_write(&ddev->lock);
+	ddev->dev = NULL;
+	ddev->ctrl = NULL;
+	up_write(&ddev->lock);
+
+	/* Finally remove the misc-device. */
+	misc_deregister(&ddev->mdev);
+
+	/*
+	 * We're now guaranteed that sdtx_device_open() won't be called any
+	 * more, so we can now drop out reference.
+	 */
+	sdtx_device_put(ddev);
+}
+
+
+/* -- PM ops. --------------------------------------------------------------- */
+
+#ifdef CONFIG_PM_SLEEP
+
+static void surface_dtx_pm_complete(struct device *dev)
+{
+	struct sdtx_device *ddev = dev_get_drvdata(dev);
+
+	/*
+	 * Normally, the EC will store events while suspended (i.e. in
+	 * display-off state) and release them when resumed (i.e. transitioned
+	 * to display-on state). During hibernation, however, the EC will be
+	 * shut down and does not store events. Furthermore, events might be
+	 * dropped during prolonged suspension (it is currently unknown how
+	 * big this event buffer is and how it behaves on overruns).
+	 *
+	 * To prevent any problems, we update the device state here. We do
+	 * this delayed to ensure that any events sent by the EC directly
+	 * after resuming will be handled first. The delay below has been
+	 * chosen (experimentally), so that there should be ample time for
+	 * these events to be handled, before we check and, if necessary,
+	 * update the state.
+	 */
+	sdtx_update_device_state(ddev, msecs_to_jiffies(1000));
+}
+
+static const struct dev_pm_ops surface_dtx_pm_ops = {
+	.complete = surface_dtx_pm_complete,
+};
+
+#else /* CONFIG_PM_SLEEP */
+
+static const struct dev_pm_ops surface_dtx_pm_ops = {};
+
+#endif /* CONFIG_PM_SLEEP */
+
+
+/* -- Platform driver. ------------------------------------------------------ */
+
+static int surface_dtx_platform_probe(struct platform_device *pdev)
+{
+	struct ssam_controller *ctrl;
+	struct sdtx_device *ddev;
+
+	/* Link to EC. */
+	ctrl = ssam_client_bind(&pdev->dev);
+	if (IS_ERR(ctrl))
+		return PTR_ERR(ctrl) == -ENODEV ? -EPROBE_DEFER : PTR_ERR(ctrl);
+
+	ddev = sdtx_device_create(&pdev->dev, ctrl);
+	if (IS_ERR(ddev))
+		return PTR_ERR(ddev);
+
+	platform_set_drvdata(pdev, ddev);
+	return 0;
+}
+
+static int surface_dtx_platform_remove(struct platform_device *pdev)
+{
+	sdtx_device_destroy(platform_get_drvdata(pdev));
+	return 0;
+}
+
+static const struct acpi_device_id surface_dtx_acpi_match[] = {
+	{ "MSHW0133", 0 },
+	{ },
+};
+MODULE_DEVICE_TABLE(acpi, surface_dtx_acpi_match);
+
+static struct platform_driver surface_dtx_platform_driver = {
+	.probe = surface_dtx_platform_probe,
+	.remove = surface_dtx_platform_remove,
+	.driver = {
+		.name = "surface_dtx_pltf",
+		.acpi_match_table = surface_dtx_acpi_match,
+		.pm = &surface_dtx_pm_ops,
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
+	},
+};
+
+
+/* -- SSAM device driver. --------------------------------------------------- */
+
+#ifdef CONFIG_SURFACE_AGGREGATOR_BUS
+
+static int surface_dtx_ssam_probe(struct ssam_device *sdev)
+{
+	struct sdtx_device *ddev;
+
+	ddev = sdtx_device_create(&sdev->dev, sdev->ctrl);
+	if (IS_ERR(ddev))
+		return PTR_ERR(ddev);
+
+	ssam_device_set_drvdata(sdev, ddev);
+	return 0;
+}
+
+static void surface_dtx_ssam_remove(struct ssam_device *sdev)
+{
+	sdtx_device_destroy(ssam_device_get_drvdata(sdev));
+}
+
+static const struct ssam_device_id surface_dtx_ssam_match[] = {
+	{ SSAM_SDEV(BAS, 0x01, 0x00, 0x00) },
+	{ },
+};
+MODULE_DEVICE_TABLE(ssam, surface_dtx_ssam_match);
+
+static struct ssam_device_driver surface_dtx_ssam_driver = {
+	.probe = surface_dtx_ssam_probe,
+	.remove = surface_dtx_ssam_remove,
+	.match_table = surface_dtx_ssam_match,
+	.driver = {
+		.name = "surface_dtx",
+		.pm = &surface_dtx_pm_ops,
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
+	},
+};
+
+static int ssam_dtx_driver_register(void)
+{
+	return ssam_device_driver_register(&surface_dtx_ssam_driver);
+}
+
+static void ssam_dtx_driver_unregister(void)
+{
+	ssam_device_driver_unregister(&surface_dtx_ssam_driver);
+}
+
+#else /* CONFIG_SURFACE_AGGREGATOR_BUS */
+
+static int ssam_dtx_driver_register(void)
+{
+	return 0;
+}
+
+static void ssam_dtx_driver_unregister(void)
+{
+}
+
+#endif /* CONFIG_SURFACE_AGGREGATOR_BUS */
+
+
+/* -- Module setup. --------------------------------------------------------- */
+
+static int __init surface_dtx_init(void)
+{
+	int status;
+
+	status = ssam_dtx_driver_register();
+	if (status)
+		return status;
+
+	status = platform_driver_register(&surface_dtx_platform_driver);
+	if (status)
+		ssam_dtx_driver_unregister();
+
+	return status;
+}
+module_init(surface_dtx_init);
+
+static void __exit surface_dtx_exit(void)
+{
+	platform_driver_unregister(&surface_dtx_platform_driver);
+	ssam_dtx_driver_unregister();
+}
+module_exit(surface_dtx_exit);
+
+MODULE_AUTHOR("Maximilian Luz <luzmaximilian@gmail.com>");
+MODULE_DESCRIPTION("Detachment-system driver for Surface System Aggregator Module");
+MODULE_LICENSE("GPL");