blob: 13291fb4214e82bf78cb73e8b19916a5da68faa6 [file] [log] [blame]
// 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 = {
.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[] __counted_by(capacity);
};
/* 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_free(&event_ida, minor);
return error;
}
static void 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_free(&event_ida, MINOR(dev_data->dev.devt));
hangup_device(dev_data);
}
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);