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	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
 /*
  * ACPI event handling for Wilco Embedded Controller
  *
  * Copyright 2019 Google LLC
  *
  * The Wilco Embedded Controller can create custom events that
  * are not handled as standard ACPI objects. These events can
  * contain information about changes in EC controlled features,
  * such as errors and events in the dock or display. For example,
  * an event is triggered if the dock is plugged into a display
  * incorrectly. These events are needed for telemetry and
  * diagnostics reasons, and for possibly alerting the user.
 
  * These events are triggered by the EC with an ACPI Notify(0x90),
  * and then the BIOS reads the event buffer from EC RAM via an
  * ACPI method. When the OS receives these events via ACPI,
  * it passes them along to this driver. The events are put into
  * a queue which can be read by a userspace daemon via a char device
  * that implements read() and poll(). The event queue acts as a
  * circular buffer of size 64, so if there are no userspace consumers
  * the kernel will not run out of memory. The char device will appear at
  * /dev/wilco_event{n}, where n is some small non-negative integer,
  * starting from 0. Standard ACPI events such as the battery getting
  * plugged/unplugged can also come through this path, but they are
  * dealt with via other paths, and are ignored here.
 
  * To test, you can tail the binary data with
  * $ cat /dev/wilco_event0 | hexdump -ve '1/1 "%x\n"'
  * and then create an event by plugging/unplugging the battery.
  */
 
 #include <linux/acpi.h>
 #include <linux/cdev.h>
 #include <linux/device.h>
 #include <linux/fs.h>
 #include <linux/idr.h>
 #include <linux/io.h>
 #include <linux/list.h>
 #include <linux/module.h>
 #include <linux/poll.h>
 #include <linux/spinlock.h>
 #include <linux/uaccess.h>
 #include <linux/wait.h>
 
 /* ACPI Notify event code indicating event data is available. */
 #define EC_ACPI_NOTIFY_EVENT        0x90
 /* ACPI Method to execute to retrieve event data buffer from the EC. */
 #define EC_ACPI_GET_EVENT       "QSET"
 /* Maximum number of words in event data returned by the EC. */
 #define EC_ACPI_MAX_EVENT_WORDS     6
 #define EC_ACPI_MAX_EVENT_SIZE \
     (sizeof(struct ec_event) + (EC_ACPI_MAX_EVENT_WORDS) * sizeof(u16))
 
 /* Node will appear in /dev/EVENT_DEV_NAME */
 #define EVENT_DEV_NAME      "wilco_event"
 #define EVENT_CLASS_NAME    EVENT_DEV_NAME
 #define DRV_NAME        EVENT_DEV_NAME
 #define EVENT_DEV_NAME_FMT  (EVENT_DEV_NAME "%d")
 static struct class event_class = {
     .owner  = THIS_MODULE,
     .name   = EVENT_CLASS_NAME,
 };
 
 /* Keep track of all the device numbers used. */
 #define EVENT_MAX_DEV 128
 static int event_major;
 static DEFINE_IDA(event_ida);
 
 /* Size of circular queue of events. */
 #define MAX_NUM_EVENTS 64
 
 /**
  * struct ec_event - Extended event returned by the EC.
  * @size: Number of 16bit words in structure after the size word.
  * @type: Extended event type, meaningless for us.
  * @event: Event data words.  Max count is %EC_ACPI_MAX_EVENT_WORDS.
  */
 struct ec_event {
     u16 size;
     u16 type;
     u16 event[];
 } __packed;
 
 #define ec_event_num_words(ev) (ev->size - 1)
 #define ec_event_size(ev) (sizeof(*ev) + (ec_event_num_words(ev) * sizeof(u16)))
 
 /**
  * struct ec_event_queue - Circular queue for events.
  * @capacity: Number of elements the queue can hold.
  * @head: Next index to write to.
  * @tail: Next index to read from.
  * @entries: Array of events.
  */
 struct ec_event_queue {
     int capacity;
     int head;
     int tail;
     struct ec_event *entries[];
 };
 
 /* Maximum number of events to store in ec_event_queue */
 static int queue_size = 64;
 module_param(queue_size, int, 0644);
 
 static struct ec_event_queue *event_queue_new(int capacity)
 {
     struct ec_event_queue *q;
 
     q = kzalloc(struct_size(q, entries, capacity), GFP_KERNEL);
     if (!q)
         return NULL;
 
     q->capacity = capacity;
 
     return q;
 }
 
 static inline bool event_queue_empty(struct ec_event_queue *q)
 {
     /* head==tail when both full and empty, but head==NULL when empty */
     return q->head == q->tail && !q->entries[q->head];
 }
 
 static inline bool event_queue_full(struct ec_event_queue *q)
 {
     /* head==tail when both full and empty, but head!=NULL when full */
     return q->head == q->tail && q->entries[q->head];
 }
 
 static struct ec_event *event_queue_pop(struct ec_event_queue *q)
 {
     struct ec_event *ev;
 
     if (event_queue_empty(q))
         return NULL;
 
     ev = q->entries[q->tail];
     q->entries[q->tail] = NULL;
     q->tail = (q->tail + 1) % q->capacity;
 
     return ev;
 }
 
 /*
  * If full, overwrite the oldest event and return it so the caller
  * can kfree it. If not full, return NULL.
  */
 static struct ec_event *event_queue_push(struct ec_event_queue *q,
                      struct ec_event *ev)
 {
     struct ec_event *popped = NULL;
 
     if (event_queue_full(q))
         popped = event_queue_pop(q);
     q->entries[q->head] = ev;
     q->head = (q->head + 1) % q->capacity;
 
     return popped;
 }
 
 static void event_queue_free(struct ec_event_queue *q)
 {
     struct ec_event *event;
 
     while ((event = event_queue_pop(q)) != NULL)
         kfree(event);
 
     kfree(q);
 }
 
 /**
  * struct event_device_data - Data for a Wilco EC device that responds to ACPI.
  * @events: Circular queue of EC events to be provided to userspace.
  * @queue_lock: Protect the queue from simultaneous read/writes.
  * @wq: Wait queue to notify processes when events are available or the
  *  device has been removed.
  * @cdev: Char dev that userspace reads() and polls() from.
  * @dev: Device associated with the %cdev.
  * @exist: Has the device been not been removed? Once a device has been removed,
  *     writes, reads, and new opens will fail.
  * @available: Guarantee only one client can open() file and read from queue.
  *
  * There will be one of these structs for each ACPI device registered. This data
  * is the queue of events received from ACPI that still need to be read from
  * userspace, the device and char device that userspace is using, a wait queue
  * used to notify different threads when something has changed, plus a flag
  * on whether the ACPI device has been removed.
  */
 struct event_device_data {
     struct ec_event_queue *events;
     spinlock_t queue_lock;
     wait_queue_head_t wq;
     struct device dev;
     struct cdev cdev;
     bool exist;
     atomic_t available;
 };
 
 /**
  * enqueue_events() - Place EC events in queue to be read by userspace.
  * @adev: Device the events came from.
  * @buf: Buffer of event data.
  * @length: Length of event data buffer.
  *
  * %buf contains a number of ec_event's, packed one after the other.
  * Each ec_event is of variable length. Start with the first event, copy it
  * into a persistent ec_event, store that entry in the queue, move on
  * to the next ec_event in buf, and repeat.
  *
  * Return: 0 on success or negative error code on failure.
  */
 static int enqueue_events(struct acpi_device *adev, const u8 *buf, u32 length)
 {
     struct event_device_data *dev_data = adev->driver_data;
     struct ec_event *event, *queue_event, *old_event;
     size_t num_words, event_size;
     u32 offset = 0;
 
     while (offset < length) {
         event = (struct ec_event *)(buf + offset);
 
         num_words = ec_event_num_words(event);
         event_size = ec_event_size(event);
         if (num_words > EC_ACPI_MAX_EVENT_WORDS) {
             dev_err(&adev->dev, "Too many event words: %zu > %d\n",
                 num_words, EC_ACPI_MAX_EVENT_WORDS);
             return -EOVERFLOW;
         }
 
         /* Ensure event does not overflow the available buffer */
         if ((offset + event_size) > length) {
             dev_err(&adev->dev, "Event exceeds buffer: %zu > %d\n",
                 offset + event_size, length);
             return -EOVERFLOW;
         }
 
         /* Point to the next event in the buffer */
         offset += event_size;
 
         /* Copy event into the queue */
         queue_event = kmemdup(event, event_size, GFP_KERNEL);
         if (!queue_event)
             return -ENOMEM;
         spin_lock(&dev_data->queue_lock);
         old_event = event_queue_push(dev_data->events, queue_event);
         spin_unlock(&dev_data->queue_lock);
         kfree(old_event);
         wake_up_interruptible(&dev_data->wq);
     }
 
     return 0;
 }
 
 /**
  * event_device_notify() - Callback when EC generates an event over ACPI.
  * @adev: The device that the event is coming from.
  * @value: Value passed to Notify() in ACPI.
  *
  * This function will read the events from the device and enqueue them.
  */
 static void event_device_notify(struct acpi_device *adev, u32 value)
 {
     struct acpi_buffer event_buffer = { ACPI_ALLOCATE_BUFFER, NULL };
     union acpi_object *obj;
     acpi_status status;
 
     if (value != EC_ACPI_NOTIFY_EVENT) {
         dev_err(&adev->dev, "Invalid event: 0x%08x\n", value);
         return;
     }
 
     /* Execute ACPI method to get event data buffer. */
     status = acpi_evaluate_object(adev->handle, EC_ACPI_GET_EVENT,
                       NULL, &event_buffer);
     if (ACPI_FAILURE(status)) {
         dev_err(&adev->dev, "Error executing ACPI method %s()\n",
             EC_ACPI_GET_EVENT);
         return;
     }
 
     obj = (union acpi_object *)event_buffer.pointer;
     if (!obj) {
         dev_err(&adev->dev, "Nothing returned from %s()\n",
             EC_ACPI_GET_EVENT);
         return;
     }
     if (obj->type != ACPI_TYPE_BUFFER) {
         dev_err(&adev->dev, "Invalid object returned from %s()\n",
             EC_ACPI_GET_EVENT);
         kfree(obj);
         return;
     }
     if (obj->buffer.length < sizeof(struct ec_event)) {
         dev_err(&adev->dev, "Invalid buffer length %d from %s()\n",
             obj->buffer.length, EC_ACPI_GET_EVENT);
         kfree(obj);
         return;
     }
 
     enqueue_events(adev, obj->buffer.pointer, obj->buffer.length);
     kfree(obj);
 }
 
 static int event_open(struct inode *inode, struct file *filp)
 {
     struct event_device_data *dev_data;
 
     dev_data = container_of(inode->i_cdev, struct event_device_data, cdev);
     if (!dev_data->exist)
         return -ENODEV;
 
     if (atomic_cmpxchg(&dev_data->available, 1, 0) == 0)
         return -EBUSY;
 
     /* Increase refcount on device so dev_data is not freed */
     get_device(&dev_data->dev);
     stream_open(inode, filp);
     filp->private_data = dev_data;
 
     return 0;
 }
 
 static __poll_t event_poll(struct file *filp, poll_table *wait)
 {
     struct event_device_data *dev_data = filp->private_data;
     __poll_t mask = 0;
 
     poll_wait(filp, &dev_data->wq, wait);
     if (!dev_data->exist)
         return EPOLLHUP;
     if (!event_queue_empty(dev_data->events))
         mask |= EPOLLIN | EPOLLRDNORM | EPOLLPRI;
     return mask;
 }
 
 /**
  * event_read() - Callback for passing event data to userspace via read().
  * @filp: The file we are reading from.
  * @buf: Pointer to userspace buffer to fill with one event.
  * @count: Number of bytes requested. Must be at least EC_ACPI_MAX_EVENT_SIZE.
  * @pos: File position pointer, irrelevant since we don't support seeking.
  *
  * Removes the first event from the queue, places it in the passed buffer.
  *
  * If there are no events in the queue, then one of two things happens,
  * depending on if the file was opened in nonblocking mode: If in nonblocking
  * mode, then return -EAGAIN to say there's no data. If in blocking mode, then
  * block until an event is available.
  *
  * Return: Number of bytes placed in buffer, negative error code on failure.
  */
 static ssize_t event_read(struct file *filp, char __user *buf, size_t count,
               loff_t *pos)
 {
     struct event_device_data *dev_data = filp->private_data;
     struct ec_event *event;
     ssize_t n_bytes_written = 0;
     int err;
 
     /* We only will give them the entire event at once */
     if (count != 0 && count < EC_ACPI_MAX_EVENT_SIZE)
         return -EINVAL;
 
     spin_lock(&dev_data->queue_lock);
     while (event_queue_empty(dev_data->events)) {
         spin_unlock(&dev_data->queue_lock);
         if (filp->f_flags & O_NONBLOCK)
             return -EAGAIN;
 
         err = wait_event_interruptible(dev_data->wq,
                     !event_queue_empty(dev_data->events) ||
                     !dev_data->exist);
         if (err)
             return err;
 
         /* Device was removed as we waited? */
         if (!dev_data->exist)
             return -ENODEV;
         spin_lock(&dev_data->queue_lock);
     }
     event = event_queue_pop(dev_data->events);
     spin_unlock(&dev_data->queue_lock);
     n_bytes_written = ec_event_size(event);
     if (copy_to_user(buf, event, n_bytes_written))
         n_bytes_written = -EFAULT;
     kfree(event);
 
     return n_bytes_written;
 }
 
 static int event_release(struct inode *inode, struct file *filp)
 {
     struct event_device_data *dev_data = filp->private_data;
 
     atomic_set(&dev_data->available, 1);
     put_device(&dev_data->dev);
 
     return 0;
 }
 
 static const struct file_operations event_fops = {
     .open = event_open,
     .poll  = event_poll,
     .read = event_read,
     .release = event_release,
     .llseek = no_llseek,
     .owner = THIS_MODULE,
 };
 
 /**
  * free_device_data() - Callback to free the event_device_data structure.
  * @d: The device embedded in our device data, which we have been ref counting.
  *
  * This is called only after event_device_remove() has been called and all
  * userspace programs have called event_release() on all the open file
  * descriptors.
  */
 static void free_device_data(struct device *d)
 {
     struct event_device_data *dev_data;
 
     dev_data = container_of(d, struct event_device_data, dev);
     event_queue_free(dev_data->events);
     kfree(dev_data);
 }
 
 static void hangup_device(struct event_device_data *dev_data)
 {
     dev_data->exist = false;
     /* Wake up the waiting processes so they can close. */
     wake_up_interruptible(&dev_data->wq);
     put_device(&dev_data->dev);
 }
 
 /**
  * event_device_add() - Callback when creating a new device.
  * @adev: ACPI device that we will be receiving events from.
  *
  * This finds a free minor number for the device, allocates and initializes
  * some device data, and creates a new device and char dev node.
  *
  * The device data is freed in free_device_data(), which is called when
  * %dev_data->dev is release()ed. This happens after all references to
  * %dev_data->dev are dropped, which happens once both event_device_remove()
  * has been called and every open()ed file descriptor has been release()ed.
  *
  * Return: 0 on success, negative error code on failure.
  */
 static int event_device_add(struct acpi_device *adev)
 {
     struct event_device_data *dev_data;
     int error, minor;
 
     minor = ida_alloc_max(&event_ida, EVENT_MAX_DEV-1, GFP_KERNEL);
     if (minor < 0) {
         error = minor;
         dev_err(&adev->dev, "Failed to find minor number: %d\n", error);
         return error;
     }
 
     dev_data = kzalloc(sizeof(*dev_data), GFP_KERNEL);
     if (!dev_data) {
         error = -ENOMEM;
         goto free_minor;
     }
 
     /* Initialize the device data. */
     adev->driver_data = dev_data;
     dev_data->events = event_queue_new(queue_size);
     if (!dev_data->events) {
         kfree(dev_data);
         error = -ENOMEM;
         goto free_minor;
     }
     spin_lock_init(&dev_data->queue_lock);
     init_waitqueue_head(&dev_data->wq);
     dev_data->exist = true;
     atomic_set(&dev_data->available, 1);
 
     /* Initialize the device. */
     dev_data->dev.devt = MKDEV(event_major, minor);
     dev_data->dev.class = &event_class;
     dev_data->dev.release = free_device_data;
     dev_set_name(&dev_data->dev, EVENT_DEV_NAME_FMT, minor);
     device_initialize(&dev_data->dev);
 
     /* Initialize the character device, and add it to userspace. */
     cdev_init(&dev_data->cdev, &event_fops);
     error = cdev_device_add(&dev_data->cdev, &dev_data->dev);
     if (error)
         goto free_dev_data;
 
     return 0;
 
 free_dev_data:
     hangup_device(dev_data);
 free_minor:
     ida_simple_remove(&event_ida, minor);
     return error;
 }
 
 static int event_device_remove(struct acpi_device *adev)
 {
     struct event_device_data *dev_data = adev->driver_data;
 
     cdev_device_del(&dev_data->cdev, &dev_data->dev);
     ida_simple_remove(&event_ida, MINOR(dev_data->dev.devt));
     hangup_device(dev_data);
 
     return 0;
 }
 
 static const struct acpi_device_id event_acpi_ids[] = {
     { "GOOG000D", 0 },
     { }
 };
 MODULE_DEVICE_TABLE(acpi, event_acpi_ids);
 
 static struct acpi_driver event_driver = {
     .name = DRV_NAME,
     .class = DRV_NAME,
     .ids = event_acpi_ids,
     .ops = {
         .add = event_device_add,
         .notify = event_device_notify,
         .remove = event_device_remove,
     },
     .owner = THIS_MODULE,
 };
 
 static int __init event_module_init(void)
 {
     dev_t dev_num = 0;
     int ret;
 
     ret = class_register(&event_class);
     if (ret) {
         pr_err(DRV_NAME ": Failed registering class: %d\n", ret);
         return ret;
     }
 
     /* Request device numbers, starting with minor=0. Save the major num. */
     ret = alloc_chrdev_region(&dev_num, 0, EVENT_MAX_DEV, EVENT_DEV_NAME);
     if (ret) {
         pr_err(DRV_NAME ": Failed allocating dev numbers: %d\n", ret);
         goto destroy_class;
     }
     event_major = MAJOR(dev_num);
 
     ret = acpi_bus_register_driver(&event_driver);
     if (ret < 0) {
         pr_err(DRV_NAME ": Failed registering driver: %d\n", ret);
         goto unregister_region;
     }
 
     return 0;
 
 unregister_region:
     unregister_chrdev_region(MKDEV(event_major, 0), EVENT_MAX_DEV);
 destroy_class:
     class_unregister(&event_class);
     ida_destroy(&event_ida);
     return ret;
 }
 
 static void __exit event_module_exit(void)
 {
     acpi_bus_unregister_driver(&event_driver);
     unregister_chrdev_region(MKDEV(event_major, 0), EVENT_MAX_DEV);
     class_unregister(&event_class);
     ida_destroy(&event_ida);
 }
 
 module_init(event_module_init);
 module_exit(event_module_exit);
 
 MODULE_AUTHOR("Nick Crews <ncrews@chromium.org>");
 MODULE_DESCRIPTION("Wilco EC ACPI event driver");
 MODULE_LICENSE("GPL");
 MODULE_ALIAS("platform:" DRV_NAME);

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