Adding upstream version 6.1.76.upstream/6.1.76upstream

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

1 files changed, 810 insertions, 0 deletions

diff --git a/drivers/platform/surface/surface_aggregator_cdev.c b/drivers/platform/surface/surface_aggregator_cdev.c
new file mode 100644
index 000000000..492c82e69
--- /dev/null
+++ b/drivers/platform/surface/surface_aggregator_cdev.c
@@ -0,0 +1,810 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Provides user-space access to the SSAM EC via the /dev/surface/aggregator
+ * misc device. Intended for debugging and development.
+ *
+ * Copyright (C) 2020-2022 Maximilian Luz <luzmaximilian@gmail.com>
+ */
+
+#include <linux/fs.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/platform_device.h>
+#include <linux/poll.h>
+#include <linux/rwsem.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+#include <linux/vmalloc.h>
+
+#include <linux/surface_aggregator/cdev.h>
+#include <linux/surface_aggregator/controller.h>
+#include <linux/surface_aggregator/serial_hub.h>
+
+#define SSAM_CDEV_DEVICE_NAME	"surface_aggregator_cdev"
+
+
+/* -- Main structures. ------------------------------------------------------ */
+
+enum ssam_cdev_device_state {
+	SSAM_CDEV_DEVICE_SHUTDOWN_BIT = BIT(0),
+};
+
+struct ssam_cdev {
+	struct kref kref;
+	struct rw_semaphore lock;
+
+	struct device *dev;
+	struct ssam_controller *ctrl;
+	struct miscdevice mdev;
+	unsigned long flags;
+
+	struct rw_semaphore client_lock;  /* Guards client list. */
+	struct list_head client_list;
+};
+
+struct ssam_cdev_client;
+
+struct ssam_cdev_notifier {
+	struct ssam_cdev_client *client;
+	struct ssam_event_notifier nf;
+};
+
+struct ssam_cdev_client {
+	struct ssam_cdev *cdev;
+	struct list_head node;
+
+	struct mutex notifier_lock;	/* Guards notifier access for registration */
+	struct ssam_cdev_notifier *notifier[SSH_NUM_EVENTS];
+
+	struct mutex read_lock;		/* Guards FIFO buffer read access */
+	struct mutex write_lock;	/* Guards FIFO buffer write access */
+	DECLARE_KFIFO(buffer, u8, 4096);
+
+	wait_queue_head_t waitq;
+	struct fasync_struct *fasync;
+};
+
+static void __ssam_cdev_release(struct kref *kref)
+{
+	kfree(container_of(kref, struct ssam_cdev, kref));
+}
+
+static struct ssam_cdev *ssam_cdev_get(struct ssam_cdev *cdev)
+{
+	if (cdev)
+		kref_get(&cdev->kref);
+
+	return cdev;
+}
+
+static void ssam_cdev_put(struct ssam_cdev *cdev)
+{
+	if (cdev)
+		kref_put(&cdev->kref, __ssam_cdev_release);
+}
+
+
+/* -- Notifier handling. ---------------------------------------------------- */
+
+static u32 ssam_cdev_notifier(struct ssam_event_notifier *nf, const struct ssam_event *in)
+{
+	struct ssam_cdev_notifier *cdev_nf = container_of(nf, struct ssam_cdev_notifier, nf);
+	struct ssam_cdev_client *client = cdev_nf->client;
+	struct ssam_cdev_event event;
+	size_t n = struct_size(&event, data, in->length);
+
+	/* Translate event. */
+	event.target_category = in->target_category;
+	event.target_id = in->target_id;
+	event.command_id = in->command_id;
+	event.instance_id = in->instance_id;
+	event.length = in->length;
+
+	mutex_lock(&client->write_lock);
+
+	/* Make sure we have enough space. */
+	if (kfifo_avail(&client->buffer) < n) {
+		dev_warn(client->cdev->dev,
+			 "buffer full, dropping event (tc: %#04x, tid: %#04x, cid: %#04x, iid: %#04x)\n",
+			 in->target_category, in->target_id, in->command_id, in->instance_id);
+		mutex_unlock(&client->write_lock);
+		return 0;
+	}
+
+	/* Copy event header and payload. */
+	kfifo_in(&client->buffer, (const u8 *)&event, struct_size(&event, data, 0));
+	kfifo_in(&client->buffer, &in->data[0], in->length);
+
+	mutex_unlock(&client->write_lock);
+
+	/* Notify waiting readers. */
+	kill_fasync(&client->fasync, SIGIO, POLL_IN);
+	wake_up_interruptible(&client->waitq);
+
+	/*
+	 * Don't mark events as handled, this is the job of a proper driver and
+	 * not the debugging interface.
+	 */
+	return 0;
+}
+
+static int ssam_cdev_notifier_register(struct ssam_cdev_client *client, u8 tc, int priority)
+{
+	const u16 rqid = ssh_tc_to_rqid(tc);
+	const u16 event = ssh_rqid_to_event(rqid);
+	struct ssam_cdev_notifier *nf;
+	int status;
+
+	lockdep_assert_held_read(&client->cdev->lock);
+
+	/* Validate notifier target category. */
+	if (!ssh_rqid_is_event(rqid))
+		return -EINVAL;
+
+	mutex_lock(&client->notifier_lock);
+
+	/* Check if the notifier has already been registered. */
+	if (client->notifier[event]) {
+		mutex_unlock(&client->notifier_lock);
+		return -EEXIST;
+	}
+
+	/* Allocate new notifier. */
+	nf = kzalloc(sizeof(*nf), GFP_KERNEL);
+	if (!nf) {
+		mutex_unlock(&client->notifier_lock);
+		return -ENOMEM;
+	}
+
+	/*
+	 * Create a dummy notifier with the minimal required fields for
+	 * observer registration. Note that we can skip fully specifying event
+	 * and registry here as we do not need any matching and use silent
+	 * registration, which does not enable the corresponding event.
+	 */
+	nf->client = client;
+	nf->nf.base.fn = ssam_cdev_notifier;
+	nf->nf.base.priority = priority;
+	nf->nf.event.id.target_category = tc;
+	nf->nf.event.mask = 0;	/* Do not do any matching. */
+	nf->nf.flags = SSAM_EVENT_NOTIFIER_OBSERVER;
+
+	/* Register notifier. */
+	status = ssam_notifier_register(client->cdev->ctrl, &nf->nf);
+	if (status)
+		kfree(nf);
+	else
+		client->notifier[event] = nf;
+
+	mutex_unlock(&client->notifier_lock);
+	return status;
+}
+
+static int ssam_cdev_notifier_unregister(struct ssam_cdev_client *client, u8 tc)
+{
+	const u16 rqid = ssh_tc_to_rqid(tc);
+	const u16 event = ssh_rqid_to_event(rqid);
+	int status;
+
+	lockdep_assert_held_read(&client->cdev->lock);
+
+	/* Validate notifier target category. */
+	if (!ssh_rqid_is_event(rqid))
+		return -EINVAL;
+
+	mutex_lock(&client->notifier_lock);
+
+	/* Check if the notifier is currently registered. */
+	if (!client->notifier[event]) {
+		mutex_unlock(&client->notifier_lock);
+		return -ENOENT;
+	}
+
+	/* Unregister and free notifier. */
+	status = ssam_notifier_unregister(client->cdev->ctrl, &client->notifier[event]->nf);
+	kfree(client->notifier[event]);
+	client->notifier[event] = NULL;
+
+	mutex_unlock(&client->notifier_lock);
+	return status;
+}
+
+static void ssam_cdev_notifier_unregister_all(struct ssam_cdev_client *client)
+{
+	int i;
+
+	down_read(&client->cdev->lock);
+
+	/*
+	 * This function may be used during shutdown, thus we need to test for
+	 * cdev->ctrl instead of the SSAM_CDEV_DEVICE_SHUTDOWN_BIT bit.
+	 */
+	if (client->cdev->ctrl) {
+		for (i = 0; i < SSH_NUM_EVENTS; i++)
+			ssam_cdev_notifier_unregister(client, i + 1);
+
+	} else {
+		int count = 0;
+
+		/*
+		 * Device has been shut down. Any notifier remaining is a bug,
+		 * so warn about that as this would otherwise hardly be
+		 * noticeable. Nevertheless, free them as well.
+		 */
+		mutex_lock(&client->notifier_lock);
+		for (i = 0; i < SSH_NUM_EVENTS; i++) {
+			count += !!(client->notifier[i]);
+			kfree(client->notifier[i]);
+			client->notifier[i] = NULL;
+		}
+		mutex_unlock(&client->notifier_lock);
+
+		WARN_ON(count > 0);
+	}
+
+	up_read(&client->cdev->lock);
+}
+
+
+/* -- IOCTL functions. ------------------------------------------------------ */
+
+static long ssam_cdev_request(struct ssam_cdev_client *client, struct ssam_cdev_request __user *r)
+{
+	struct ssam_cdev_request rqst;
+	struct ssam_request spec = {};
+	struct ssam_response rsp = {};
+	const void __user *plddata;
+	void __user *rspdata;
+	int status = 0, ret = 0, tmp;
+
+	lockdep_assert_held_read(&client->cdev->lock);
+
+	ret = copy_struct_from_user(&rqst, sizeof(rqst), r, sizeof(*r));
+	if (ret)
+		goto out;
+
+	plddata = u64_to_user_ptr(rqst.payload.data);
+	rspdata = u64_to_user_ptr(rqst.response.data);
+
+	/* Setup basic request fields. */
+	spec.target_category = rqst.target_category;
+	spec.target_id = rqst.target_id;
+	spec.command_id = rqst.command_id;
+	spec.instance_id = rqst.instance_id;
+	spec.flags = 0;
+	spec.length = rqst.payload.length;
+	spec.payload = NULL;
+
+	if (rqst.flags & SSAM_CDEV_REQUEST_HAS_RESPONSE)
+		spec.flags |= SSAM_REQUEST_HAS_RESPONSE;
+
+	if (rqst.flags & SSAM_CDEV_REQUEST_UNSEQUENCED)
+		spec.flags |= SSAM_REQUEST_UNSEQUENCED;
+
+	rsp.capacity = rqst.response.length;
+	rsp.length = 0;
+	rsp.pointer = NULL;
+
+	/* Get request payload from user-space. */
+	if (spec.length) {
+		if (!plddata) {
+			ret = -EINVAL;
+			goto out;
+		}
+
+		/*
+		 * Note: spec.length is limited to U16_MAX bytes via struct
+		 * ssam_cdev_request. This is slightly larger than the
+		 * theoretical maximum (SSH_COMMAND_MAX_PAYLOAD_SIZE) of the
+		 * underlying protocol (note that nothing remotely this size
+		 * should ever be allocated in any normal case). This size is
+		 * validated later in ssam_request_sync(), for allocation the
+		 * bound imposed by u16 should be enough.
+		 */
+		spec.payload = kzalloc(spec.length, GFP_KERNEL);
+		if (!spec.payload) {
+			ret = -ENOMEM;
+			goto out;
+		}
+
+		if (copy_from_user((void *)spec.payload, plddata, spec.length)) {
+			ret = -EFAULT;
+			goto out;
+		}
+	}
+
+	/* Allocate response buffer. */
+	if (rsp.capacity) {
+		if (!rspdata) {
+			ret = -EINVAL;
+			goto out;
+		}
+
+		/*
+		 * Note: rsp.capacity is limited to U16_MAX bytes via struct
+		 * ssam_cdev_request. This is slightly larger than the
+		 * theoretical maximum (SSH_COMMAND_MAX_PAYLOAD_SIZE) of the
+		 * underlying protocol (note that nothing remotely this size
+		 * should ever be allocated in any normal case). In later use,
+		 * this capacity does not have to be strictly bounded, as it
+		 * is only used as an output buffer to be written to. For
+		 * allocation the bound imposed by u16 should be enough.
+		 */
+		rsp.pointer = kzalloc(rsp.capacity, GFP_KERNEL);
+		if (!rsp.pointer) {
+			ret = -ENOMEM;
+			goto out;
+		}
+	}
+
+	/* Perform request. */
+	status = ssam_request_sync(client->cdev->ctrl, &spec, &rsp);
+	if (status)
+		goto out;
+
+	/* Copy response to user-space. */
+	if (rsp.length && copy_to_user(rspdata, rsp.pointer, rsp.length))
+		ret = -EFAULT;
+
+out:
+	/* Always try to set response-length and status. */
+	tmp = put_user(rsp.length, &r->response.length);
+	if (tmp)
+		ret = tmp;
+
+	tmp = put_user(status, &r->status);
+	if (tmp)
+		ret = tmp;
+
+	/* Cleanup. */
+	kfree(spec.payload);
+	kfree(rsp.pointer);
+
+	return ret;
+}
+
+static long ssam_cdev_notif_register(struct ssam_cdev_client *client,
+				     const struct ssam_cdev_notifier_desc __user *d)
+{
+	struct ssam_cdev_notifier_desc desc;
+	long ret;
+
+	lockdep_assert_held_read(&client->cdev->lock);
+
+	ret = copy_struct_from_user(&desc, sizeof(desc), d, sizeof(*d));
+	if (ret)
+		return ret;
+
+	return ssam_cdev_notifier_register(client, desc.target_category, desc.priority);
+}
+
+static long ssam_cdev_notif_unregister(struct ssam_cdev_client *client,
+				       const struct ssam_cdev_notifier_desc __user *d)
+{
+	struct ssam_cdev_notifier_desc desc;
+	long ret;
+
+	lockdep_assert_held_read(&client->cdev->lock);
+
+	ret = copy_struct_from_user(&desc, sizeof(desc), d, sizeof(*d));
+	if (ret)
+		return ret;
+
+	return ssam_cdev_notifier_unregister(client, desc.target_category);
+}
+
+static long ssam_cdev_event_enable(struct ssam_cdev_client *client,
+				   const struct ssam_cdev_event_desc __user *d)
+{
+	struct ssam_cdev_event_desc desc;
+	struct ssam_event_registry reg;
+	struct ssam_event_id id;
+	long ret;
+
+	lockdep_assert_held_read(&client->cdev->lock);
+
+	/* Read descriptor from user-space. */
+	ret = copy_struct_from_user(&desc, sizeof(desc), d, sizeof(*d));
+	if (ret)
+		return ret;
+
+	/* Translate descriptor. */
+	reg.target_category = desc.reg.target_category;
+	reg.target_id = desc.reg.target_id;
+	reg.cid_enable = desc.reg.cid_enable;
+	reg.cid_disable = desc.reg.cid_disable;
+
+	id.target_category = desc.id.target_category;
+	id.instance = desc.id.instance;
+
+	/* Disable event. */
+	return ssam_controller_event_enable(client->cdev->ctrl, reg, id, desc.flags);
+}
+
+static long ssam_cdev_event_disable(struct ssam_cdev_client *client,
+				    const struct ssam_cdev_event_desc __user *d)
+{
+	struct ssam_cdev_event_desc desc;
+	struct ssam_event_registry reg;
+	struct ssam_event_id id;
+	long ret;
+
+	lockdep_assert_held_read(&client->cdev->lock);
+
+	/* Read descriptor from user-space. */
+	ret = copy_struct_from_user(&desc, sizeof(desc), d, sizeof(*d));
+	if (ret)
+		return ret;
+
+	/* Translate descriptor. */
+	reg.target_category = desc.reg.target_category;
+	reg.target_id = desc.reg.target_id;
+	reg.cid_enable = desc.reg.cid_enable;
+	reg.cid_disable = desc.reg.cid_disable;
+
+	id.target_category = desc.id.target_category;
+	id.instance = desc.id.instance;
+
+	/* Disable event. */
+	return ssam_controller_event_disable(client->cdev->ctrl, reg, id, desc.flags);
+}
+
+
+/* -- File operations. ------------------------------------------------------ */
+
+static int ssam_cdev_device_open(struct inode *inode, struct file *filp)
+{
+	struct miscdevice *mdev = filp->private_data;
+	struct ssam_cdev_client *client;
+	struct ssam_cdev *cdev = container_of(mdev, struct ssam_cdev, mdev);
+
+	/* Initialize client */
+	client = vzalloc(sizeof(*client));
+	if (!client)
+		return -ENOMEM;
+
+	client->cdev = ssam_cdev_get(cdev);
+
+	INIT_LIST_HEAD(&client->node);
+
+	mutex_init(&client->notifier_lock);
+
+	mutex_init(&client->read_lock);
+	mutex_init(&client->write_lock);
+	INIT_KFIFO(client->buffer);
+	init_waitqueue_head(&client->waitq);
+
+	filp->private_data = client;
+
+	/* Attach client. */
+	down_write(&cdev->client_lock);
+
+	if (test_bit(SSAM_CDEV_DEVICE_SHUTDOWN_BIT, &cdev->flags)) {
+		up_write(&cdev->client_lock);
+		mutex_destroy(&client->write_lock);
+		mutex_destroy(&client->read_lock);
+		mutex_destroy(&client->notifier_lock);
+		ssam_cdev_put(client->cdev);
+		vfree(client);
+		return -ENODEV;
+	}
+	list_add_tail(&client->node, &cdev->client_list);
+
+	up_write(&cdev->client_lock);
+
+	stream_open(inode, filp);
+	return 0;
+}
+
+static int ssam_cdev_device_release(struct inode *inode, struct file *filp)
+{
+	struct ssam_cdev_client *client = filp->private_data;
+
+	/* Force-unregister all remaining notifiers of this client. */
+	ssam_cdev_notifier_unregister_all(client);
+
+	/* Detach client. */
+	down_write(&client->cdev->client_lock);
+	list_del(&client->node);
+	up_write(&client->cdev->client_lock);
+
+	/* Free client. */
+	mutex_destroy(&client->write_lock);
+	mutex_destroy(&client->read_lock);
+
+	mutex_destroy(&client->notifier_lock);
+
+	ssam_cdev_put(client->cdev);
+	vfree(client);
+
+	return 0;
+}
+
+static long __ssam_cdev_device_ioctl(struct ssam_cdev_client *client, unsigned int cmd,
+				     unsigned long arg)
+{
+	lockdep_assert_held_read(&client->cdev->lock);
+
+	switch (cmd) {
+	case SSAM_CDEV_REQUEST:
+		return ssam_cdev_request(client, (struct ssam_cdev_request __user *)arg);
+
+	case SSAM_CDEV_NOTIF_REGISTER:
+		return ssam_cdev_notif_register(client,
+						(struct ssam_cdev_notifier_desc __user *)arg);
+
+	case SSAM_CDEV_NOTIF_UNREGISTER:
+		return ssam_cdev_notif_unregister(client,
+						  (struct ssam_cdev_notifier_desc __user *)arg);
+
+	case SSAM_CDEV_EVENT_ENABLE:
+		return ssam_cdev_event_enable(client, (struct ssam_cdev_event_desc __user *)arg);
+
+	case SSAM_CDEV_EVENT_DISABLE:
+		return ssam_cdev_event_disable(client, (struct ssam_cdev_event_desc __user *)arg);
+
+	default:
+		return -ENOTTY;
+	}
+}
+
+static long ssam_cdev_device_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+	struct ssam_cdev_client *client = file->private_data;
+	long status;
+
+	/* Ensure that controller is valid for as long as we need it. */
+	if (down_read_killable(&client->cdev->lock))
+		return -ERESTARTSYS;
+
+	if (test_bit(SSAM_CDEV_DEVICE_SHUTDOWN_BIT, &client->cdev->flags)) {
+		up_read(&client->cdev->lock);
+		return -ENODEV;
+	}
+
+	status = __ssam_cdev_device_ioctl(client, cmd, arg);
+
+	up_read(&client->cdev->lock);
+	return status;
+}
+
+static ssize_t ssam_cdev_read(struct file *file, char __user *buf, size_t count, loff_t *offs)
+{
+	struct ssam_cdev_client *client = file->private_data;
+	struct ssam_cdev *cdev = client->cdev;
+	unsigned int copied;
+	int status = 0;
+
+	if (down_read_killable(&cdev->lock))
+		return -ERESTARTSYS;
+
+	/* Make sure we're not shut down. */
+	if (test_bit(SSAM_CDEV_DEVICE_SHUTDOWN_BIT, &cdev->flags)) {
+		up_read(&cdev->lock);
+		return -ENODEV;
+	}
+
+	do {
+		/* Check availability, wait if necessary. */
+		if (kfifo_is_empty(&client->buffer)) {
+			up_read(&cdev->lock);
+
+			if (file->f_flags & O_NONBLOCK)
+				return -EAGAIN;
+
+			status = wait_event_interruptible(client->waitq,
+							  !kfifo_is_empty(&client->buffer) ||
+							  test_bit(SSAM_CDEV_DEVICE_SHUTDOWN_BIT,
+								   &cdev->flags));
+			if (status < 0)
+				return status;
+
+			if (down_read_killable(&cdev->lock))
+				return -ERESTARTSYS;
+
+			/* Need to check that we're not shut down again. */
+			if (test_bit(SSAM_CDEV_DEVICE_SHUTDOWN_BIT, &cdev->flags)) {
+				up_read(&cdev->lock);
+				return -ENODEV;
+			}
+		}
+
+		/* Try to read from FIFO. */
+		if (mutex_lock_interruptible(&client->read_lock)) {
+			up_read(&cdev->lock);
+			return -ERESTARTSYS;
+		}
+
+		status = kfifo_to_user(&client->buffer, buf, count, &copied);
+		mutex_unlock(&client->read_lock);
+
+		if (status < 0) {
+			up_read(&cdev->lock);
+			return status;
+		}
+
+		/* We might not have gotten anything, check this here. */
+		if (copied == 0 && (file->f_flags & O_NONBLOCK)) {
+			up_read(&cdev->lock);
+			return -EAGAIN;
+		}
+	} while (copied == 0);
+
+	up_read(&cdev->lock);
+	return copied;
+}
+
+static __poll_t ssam_cdev_poll(struct file *file, struct poll_table_struct *pt)
+{
+	struct ssam_cdev_client *client = file->private_data;
+	__poll_t events = 0;
+
+	if (test_bit(SSAM_CDEV_DEVICE_SHUTDOWN_BIT, &client->cdev->flags))
+		return EPOLLHUP | EPOLLERR;
+
+	poll_wait(file, &client->waitq, pt);
+
+	if (!kfifo_is_empty(&client->buffer))
+		events |= EPOLLIN | EPOLLRDNORM;
+
+	return events;
+}
+
+static int ssam_cdev_fasync(int fd, struct file *file, int on)
+{
+	struct ssam_cdev_client *client = file->private_data;
+
+	return fasync_helper(fd, file, on, &client->fasync);
+}
+
+static const struct file_operations ssam_controller_fops = {
+	.owner          = THIS_MODULE,
+	.open           = ssam_cdev_device_open,
+	.release        = ssam_cdev_device_release,
+	.read           = ssam_cdev_read,
+	.poll           = ssam_cdev_poll,
+	.fasync         = ssam_cdev_fasync,
+	.unlocked_ioctl = ssam_cdev_device_ioctl,
+	.compat_ioctl   = ssam_cdev_device_ioctl,
+	.llseek         = no_llseek,
+};
+
+
+/* -- Device and driver setup ----------------------------------------------- */
+
+static int ssam_dbg_device_probe(struct platform_device *pdev)
+{
+	struct ssam_controller *ctrl;
+	struct ssam_cdev *cdev;
+	int status;
+
+	ctrl = ssam_client_bind(&pdev->dev);
+	if (IS_ERR(ctrl))
+		return PTR_ERR(ctrl) == -ENODEV ? -EPROBE_DEFER : PTR_ERR(ctrl);
+
+	cdev = kzalloc(sizeof(*cdev), GFP_KERNEL);
+	if (!cdev)
+		return -ENOMEM;
+
+	kref_init(&cdev->kref);
+	init_rwsem(&cdev->lock);
+	cdev->ctrl = ctrl;
+	cdev->dev = &pdev->dev;
+
+	cdev->mdev.parent   = &pdev->dev;
+	cdev->mdev.minor    = MISC_DYNAMIC_MINOR;
+	cdev->mdev.name     = "surface_aggregator";
+	cdev->mdev.nodename = "surface/aggregator";
+	cdev->mdev.fops     = &ssam_controller_fops;
+
+	init_rwsem(&cdev->client_lock);
+	INIT_LIST_HEAD(&cdev->client_list);
+
+	status = misc_register(&cdev->mdev);
+	if (status) {
+		kfree(cdev);
+		return status;
+	}
+
+	platform_set_drvdata(pdev, cdev);
+	return 0;
+}
+
+static int ssam_dbg_device_remove(struct platform_device *pdev)
+{
+	struct ssam_cdev *cdev = platform_get_drvdata(pdev);
+	struct ssam_cdev_client *client;
+
+	/*
+	 * Mark device as shut-down. Prevent new clients from being added and
+	 * new operations from being executed.
+	 */
+	set_bit(SSAM_CDEV_DEVICE_SHUTDOWN_BIT, &cdev->flags);
+
+	down_write(&cdev->client_lock);
+
+	/* Remove all notifiers registered by us. */
+	list_for_each_entry(client, &cdev->client_list, node) {
+		ssam_cdev_notifier_unregister_all(client);
+	}
+
+	/* Wake up async clients. */
+	list_for_each_entry(client, &cdev->client_list, node) {
+		kill_fasync(&client->fasync, SIGIO, POLL_HUP);
+	}
+
+	/* Wake up blocking clients. */
+	list_for_each_entry(client, &cdev->client_list, node) {
+		wake_up_interruptible(&client->waitq);
+	}
+
+	up_write(&cdev->client_lock);
+
+	/*
+	 * The controller is only guaranteed to be valid for as long as the
+	 * driver is bound. Remove controller so that any lingering open files
+	 * cannot access it any more after we're gone.
+	 */
+	down_write(&cdev->lock);
+	cdev->ctrl = NULL;
+	cdev->dev = NULL;
+	up_write(&cdev->lock);
+
+	misc_deregister(&cdev->mdev);
+
+	ssam_cdev_put(cdev);
+	return 0;
+}
+
+static struct platform_device *ssam_cdev_device;
+
+static struct platform_driver ssam_cdev_driver = {
+	.probe = ssam_dbg_device_probe,
+	.remove = ssam_dbg_device_remove,
+	.driver = {
+		.name = SSAM_CDEV_DEVICE_NAME,
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
+	},
+};
+
+static int __init ssam_debug_init(void)
+{
+	int status;
+
+	ssam_cdev_device = platform_device_alloc(SSAM_CDEV_DEVICE_NAME,
+						 PLATFORM_DEVID_NONE);
+	if (!ssam_cdev_device)
+		return -ENOMEM;
+
+	status = platform_device_add(ssam_cdev_device);
+	if (status)
+		goto err_device;
+
+	status = platform_driver_register(&ssam_cdev_driver);
+	if (status)
+		goto err_driver;
+
+	return 0;
+
+err_driver:
+	platform_device_del(ssam_cdev_device);
+err_device:
+	platform_device_put(ssam_cdev_device);
+	return status;
+}
+module_init(ssam_debug_init);
+
+static void __exit ssam_debug_exit(void)
+{
+	platform_driver_unregister(&ssam_cdev_driver);
+	platform_device_unregister(ssam_cdev_device);
+}
+module_exit(ssam_debug_exit);
+
+MODULE_AUTHOR("Maximilian Luz <luzmaximilian@gmail.com>");
+MODULE_DESCRIPTION("User-space interface for Surface System Aggregator Module");
+MODULE_LICENSE("GPL");