diff options
| -rw-r--r-- | drivers/platform/chrome/wilco_ec/Kconfig | 9 | ||||
| -rw-r--r-- | drivers/platform/chrome/wilco_ec/Makefile | 2 | ||||
| -rw-r--r-- | drivers/platform/chrome/wilco_ec/event.c | 541 |
3 files changed, 552 insertions, 0 deletions
diff --git a/drivers/platform/chrome/wilco_ec/Kconfig b/drivers/platform/chrome/wilco_ec/Kconfig index e09e4cebe9b4..2c8f6f15f28f 100644 --- a/drivers/platform/chrome/wilco_ec/Kconfig +++ b/drivers/platform/chrome/wilco_ec/Kconfig @@ -18,3 +18,12 @@ config WILCO_EC_DEBUGFS manipulation and allow for testing arbitrary commands. This interface is intended for debug only and will not be present on production devices. + +config WILCO_EC_EVENTS + tristate "Enable event forwarding from EC to userspace" + depends on WILCO_EC + help + If you say Y here, you get support for the EC to send events + (such as power state changes) to userspace. The EC sends the events + over ACPI, and a driver queues up the events to be read by a + userspace daemon from /dev/wilco_event using read() and poll(). diff --git a/drivers/platform/chrome/wilco_ec/Makefile b/drivers/platform/chrome/wilco_ec/Makefile index 72df9b5e1983..4d8a5f068f8b 100644 --- a/drivers/platform/chrome/wilco_ec/Makefile +++ b/drivers/platform/chrome/wilco_ec/Makefile @@ -4,3 +4,5 @@ wilco_ec-objs := core.o mailbox.o properties.o sysfs.o obj-$(CONFIG_WILCO_EC) += wilco_ec.o wilco_ec_debugfs-objs := debugfs.o obj-$(CONFIG_WILCO_EC_DEBUGFS) += wilco_ec_debugfs.o +wilco_ec_events-objs := event.o +obj-$(CONFIG_WILCO_EC_EVENTS) += wilco_ec_events.o diff --git a/drivers/platform/chrome/wilco_ec/event.c b/drivers/platform/chrome/wilco_ec/event.c new file mode 100644 index 000000000000..4d2776f77dbd --- /dev/null +++ b/drivers/platform/chrome/wilco_ec/event.c @@ -0,0 +1,541 @@ +// 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/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 event_device_data - Data for a Wilco EC device that responds to ACPI. + * @events: Circular queue of EC events to be provided to userspace. + * @num_events: Number of events in the queue. + * @lock: Mutex to guard the queue. + * @wq: Wait queue to notify processes when events or 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 (plus a supporting lock and wait queue), as well as the device and + * char device that userspace is using, plus a flag on whether the ACPI device + * has been removed. + */ +struct event_device_data { + struct list_head events; + size_t num_events; + struct mutex lock; + wait_queue_head_t wq; + struct device dev; + struct cdev cdev; + bool exist; + atomic_t available; +}; + +/** + * struct ec_event - Extended event returned by the EC. + * @size: Number of words in structure after the size word. + * @type: Extended event type from &enum ec_event_type. + * @event: Event data words. Max count is %EC_ACPI_MAX_EVENT_WORDS. + */ +struct ec_event { + u16 size; + u16 type; + u16 event[0]; +} __packed; + +/** + * struct ec_event_entry - Event queue entry. + * @list: List node. + * @size: Number of bytes in event structure. + * @event: Extended event returned by the EC. This should be the last + * element because &struct ec_event includes a zero length array. + */ +struct ec_event_entry { + struct list_head list; + size_t size; + struct ec_event event; +}; + +/** + * 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 containing ev_event_entry, store that entry in a list, 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; + struct ec_event_entry *entry, *oldest_entry; + size_t event_size, num_words, word_size; + u32 offset = 0; + + while (offset < length) { + event = (struct ec_event *)(buf + offset); + if (!event) + return -EINVAL; + + /* Number of 16bit event data words is size - 1 */ + num_words = event->size - 1; + word_size = num_words * sizeof(u16); + event_size = sizeof(*event) + word_size; + 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; + + /* Create event entry for the queue */ + entry = kzalloc(sizeof(struct ec_event_entry) + word_size, + GFP_KERNEL); + if (!entry) + return -ENOMEM; + entry->size = event_size; + memcpy(&entry->event, event, entry->size); + + mutex_lock(&dev_data->lock); + + /* If the queue is full, delete the oldest event */ + if (dev_data->num_events >= MAX_NUM_EVENTS) { + oldest_entry = list_first_entry(&dev_data->events, + struct ec_event_entry, + list); + list_del(&oldest_entry->list); + kfree(oldest_entry); + dev_data->num_events--; + } + + /* Add this event to the queue */ + list_add_tail(&entry->list, &dev_data->events); + dev_data->num_events++; + + mutex_unlock(&dev_data->lock); + } + + 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 }; + struct event_device_data *dev_data = adev->driver_data; + 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); + + if (dev_data->num_events) + wake_up_interruptible(&dev_data->wq); +} + +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); + nonseekable_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 (dev_data->num_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. + * + * Fills the passed buffer with the data from the first event in the queue, + * removes that event from the queue. On error, the event remains in the queue. + * + * If there are no events in the 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_entry *entry; + 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; + + mutex_lock(&dev_data->lock); + + while (dev_data->num_events == 0) { + if (filp->f_flags & O_NONBLOCK) { + mutex_unlock(&dev_data->lock); + return -EAGAIN; + } + /* Need to unlock so that data can actually get added to the + * queue, and since we recheck before use and it's just + * comparing pointers, this is safe unlocked. + */ + mutex_unlock(&dev_data->lock); + err = wait_event_interruptible(dev_data->wq, + dev_data->num_events); + if (err) + return err; + + /* Device was removed as we waited? */ + if (!dev_data->exist) + return -ENODEV; + mutex_lock(&dev_data->lock); + } + + entry = list_first_entry(&dev_data->events, + struct ec_event_entry, list); + n_bytes_written = entry->size; + if (copy_to_user(buf, &entry->event, n_bytes_written)) + return -EFAULT; + list_del(&entry->list); + kfree(entry); + dev_data->num_events--; + + mutex_unlock(&dev_data->lock); + + 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); + kfree(dev_data); +} + +static void hangup_device(struct event_device_data *dev_data) +{ + mutex_lock(&dev_data->lock); + dev_data->exist = false; + mutex_unlock(&dev_data->lock); + + /* 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", 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; + INIT_LIST_HEAD(&dev_data->events); + mutex_init(&dev_data->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", 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", 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); |