OSCL-LXR linux-6.0.1/​drivers/​platform/​surface/​surface_aggregator_cdev.c	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // 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");

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