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// SPDX-License-Identifier: GPL-2.0
/*
* Telemetry communication for Wilco EC
*
* Copyright 2019 Google LLC
*
* The Wilco Embedded Controller is able to send telemetry data
* which is useful for enterprise applications. A daemon running on
* the OS sends a command to the EC via a write() to a char device,
* and can read the response with a read(). The write() request is
* verified by the driver to ensure that it is performing only one
* of the allowlisted commands, and that no extraneous data is
* being transmitted to the EC. The response is passed directly
* back to the reader with no modification.
*
* The character device will appear as /dev/wilco_telemN, where N
* is some small non-negative integer, starting with 0. Only one
* process may have the file descriptor open at a time. The calling
* userspace program needs to keep the device file descriptor open
* between the calls to write() and read() in order to preserve the
* response. Up to 32 bytes will be available for reading.
*
* For testing purposes, try requesting the EC's firmware build
* date, by sending the WILCO_EC_TELEM_GET_VERSION command with
* argument index=3. i.e. write [0x38, 0x00, 0x03]
* to the device node. An ASCII string of the build date is
* returned.
*/
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/fs.h>
#include <linux/module.h>
#include <linux/platform_data/wilco-ec.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/uaccess.h>
#define TELEM_DEV_NAME "wilco_telem"
#define TELEM_CLASS_NAME TELEM_DEV_NAME
#define DRV_NAME TELEM_DEV_NAME
#define TELEM_DEV_NAME_FMT (TELEM_DEV_NAME "%d")
static struct class telem_class = {
.owner = THIS_MODULE,
.name = TELEM_CLASS_NAME,
};
/* Keep track of all the device numbers used. */
#define TELEM_MAX_DEV 128
static int telem_major;
static DEFINE_IDA(telem_ida);
/* EC telemetry command codes */
#define WILCO_EC_TELEM_GET_LOG 0x99
#define WILCO_EC_TELEM_GET_VERSION 0x38
#define WILCO_EC_TELEM_GET_FAN_INFO 0x2E
#define WILCO_EC_TELEM_GET_DIAG_INFO 0xFA
#define WILCO_EC_TELEM_GET_TEMP_INFO 0x95
#define WILCO_EC_TELEM_GET_TEMP_READ 0x2C
#define WILCO_EC_TELEM_GET_BATT_EXT_INFO 0x07
#define WILCO_EC_TELEM_GET_BATT_PPID_INFO 0x8A
#define TELEM_ARGS_SIZE_MAX 30
/*
* The following telem_args_get_* structs are embedded within the |args| field
* of wilco_ec_telem_request.
*/
struct telem_args_get_log {
u8 log_type;
u8 log_index;
} __packed;
/*
* Get a piece of info about the EC firmware version:
* 0 = label
* 1 = svn_rev
* 2 = model_no
* 3 = build_date
* 4 = frio_version
*/
struct telem_args_get_version {
u8 index;
} __packed;
struct telem_args_get_fan_info {
u8 command;
u8 fan_number;
u8 arg;
} __packed;
struct telem_args_get_diag_info {
u8 type;
u8 sub_type;
} __packed;
struct telem_args_get_temp_info {
u8 command;
u8 index;
u8 field;
u8 zone;
} __packed;
struct telem_args_get_temp_read {
u8 sensor_index;
} __packed;
struct telem_args_get_batt_ext_info {
u8 var_args[5];
} __packed;
struct telem_args_get_batt_ppid_info {
u8 always1; /* Should always be 1 */
} __packed;
/**
* struct wilco_ec_telem_request - Telemetry command and arguments sent to EC.
* @command: One of WILCO_EC_TELEM_GET_* command codes.
* @reserved: Must be 0.
* @args: The first N bytes are one of telem_args_get_* structs, the rest is 0.
*/
struct wilco_ec_telem_request {
u8 command;
u8 reserved;
union {
u8 buf[TELEM_ARGS_SIZE_MAX];
struct telem_args_get_log get_log;
struct telem_args_get_version get_version;
struct telem_args_get_fan_info get_fan_info;
struct telem_args_get_diag_info get_diag_info;
struct telem_args_get_temp_info get_temp_info;
struct telem_args_get_temp_read get_temp_read;
struct telem_args_get_batt_ext_info get_batt_ext_info;
struct telem_args_get_batt_ppid_info get_batt_ppid_info;
} args;
} __packed;
/**
* check_telem_request() - Ensure that a request from userspace is valid.
* @rq: Request buffer copied from userspace.
* @size: Number of bytes copied from userspace.
*
* Return: 0 if valid, -EINVAL if bad command or reserved byte is non-zero,
* -EMSGSIZE if the request is too long.
*
* We do not want to allow userspace to send arbitrary telemetry commands to
* the EC. Therefore we check to ensure that
* 1. The request follows the format of struct wilco_ec_telem_request.
* 2. The supplied command code is one of the allowlisted commands.
* 3. The request only contains the necessary data for the header and arguments.
*/
static int check_telem_request(struct wilco_ec_telem_request *rq,
size_t size)
{
size_t max_size = offsetof(struct wilco_ec_telem_request, args);
if (rq->reserved)
return -EINVAL;
switch (rq->command) {
case WILCO_EC_TELEM_GET_LOG:
max_size += sizeof(rq->args.get_log);
break;
case WILCO_EC_TELEM_GET_VERSION:
max_size += sizeof(rq->args.get_version);
break;
case WILCO_EC_TELEM_GET_FAN_INFO:
max_size += sizeof(rq->args.get_fan_info);
break;
case WILCO_EC_TELEM_GET_DIAG_INFO:
max_size += sizeof(rq->args.get_diag_info);
break;
case WILCO_EC_TELEM_GET_TEMP_INFO:
max_size += sizeof(rq->args.get_temp_info);
break;
case WILCO_EC_TELEM_GET_TEMP_READ:
max_size += sizeof(rq->args.get_temp_read);
break;
case WILCO_EC_TELEM_GET_BATT_EXT_INFO:
max_size += sizeof(rq->args.get_batt_ext_info);
break;
case WILCO_EC_TELEM_GET_BATT_PPID_INFO:
if (rq->args.get_batt_ppid_info.always1 != 1)
return -EINVAL;
max_size += sizeof(rq->args.get_batt_ppid_info);
break;
default:
return -EINVAL;
}
return (size <= max_size) ? 0 : -EMSGSIZE;
}
/**
* struct telem_device_data - Data for a Wilco EC device that queries telemetry.
* @cdev: Char dev that userspace reads and polls from.
* @dev: Device associated with the %cdev.
* @ec: Wilco EC that we will be communicating with using the mailbox interface.
* @available: Boolean of if the device can be opened.
*/
struct telem_device_data {
struct device dev;
struct cdev cdev;
struct wilco_ec_device *ec;
atomic_t available;
};
#define TELEM_RESPONSE_SIZE EC_MAILBOX_DATA_SIZE
/**
* struct telem_session_data - Data that exists between open() and release().
* @dev_data: Pointer to get back to the device data and EC.
* @request: Command and arguments sent to EC.
* @response: Response buffer of data from EC.
* @has_msg: Is there data available to read from a previous write?
*/
struct telem_session_data {
struct telem_device_data *dev_data;
struct wilco_ec_telem_request request;
u8 response[TELEM_RESPONSE_SIZE];
bool has_msg;
};
/**
* telem_open() - Callback for when the device node is opened.
* @inode: inode for this char device node.
* @filp: file for this char device node.
*
* We need to ensure that after writing a command to the device,
* the same userspace process reads the corresponding result.
* Therefore, we increment a refcount on opening the device, so that
* only one process can communicate with the EC at a time.
*
* Return: 0 on success, or negative error code on failure.
*/
static int telem_open(struct inode *inode, struct file *filp)
{
struct telem_device_data *dev_data;
struct telem_session_data *sess_data;
/* Ensure device isn't already open */
dev_data = container_of(inode->i_cdev, struct telem_device_data, cdev);
if (atomic_cmpxchg(&dev_data->available, 1, 0) == 0)
return -EBUSY;
get_device(&dev_data->dev);
sess_data = kzalloc(sizeof(*sess_data), GFP_KERNEL);
if (!sess_data) {
atomic_set(&dev_data->available, 1);
return -ENOMEM;
}
sess_data->dev_data = dev_data;
sess_data->has_msg = false;
nonseekable_open(inode, filp);
filp->private_data = sess_data;
return 0;
}
static ssize_t telem_write(struct file *filp, const char __user *buf,
size_t count, loff_t *pos)
{
struct telem_session_data *sess_data = filp->private_data;
struct wilco_ec_message msg = {};
int ret;
if (count > sizeof(sess_data->request))
return -EMSGSIZE;
memset(&sess_data->request, 0, sizeof(sess_data->request));
if (copy_from_user(&sess_data->request, buf, count))
return -EFAULT;
ret = check_telem_request(&sess_data->request, count);
if (ret < 0)
return ret;
memset(sess_data->response, 0, sizeof(sess_data->response));
msg.type = WILCO_EC_MSG_TELEMETRY;
msg.request_data = &sess_data->request;
msg.request_size = sizeof(sess_data->request);
msg.response_data = sess_data->response;
msg.response_size = sizeof(sess_data->response);
ret = wilco_ec_mailbox(sess_data->dev_data->ec, &msg);
if (ret < 0)
return ret;
if (ret != sizeof(sess_data->response))
return -EMSGSIZE;
sess_data->has_msg = true;
return count;
}
static ssize_t telem_read(struct file *filp, char __user *buf, size_t count,
loff_t *pos)
{
struct telem_session_data *sess_data = filp->private_data;
if (!sess_data->has_msg)
return -ENODATA;
if (count > sizeof(sess_data->response))
return -EINVAL;
if (copy_to_user(buf, sess_data->response, count))
return -EFAULT;
sess_data->has_msg = false;
return count;
}
static int telem_release(struct inode *inode, struct file *filp)
{
struct telem_session_data *sess_data = filp->private_data;
atomic_set(&sess_data->dev_data->available, 1);
put_device(&sess_data->dev_data->dev);
kfree(sess_data);
return 0;
}
static const struct file_operations telem_fops = {
.open = telem_open,
.write = telem_write,
.read = telem_read,
.release = telem_release,
.llseek = no_llseek,
.owner = THIS_MODULE,
};
/**
* telem_device_free() - Callback to free the telem_device_data structure.
* @d: The device embedded in our device data, which we have been ref counting.
*
* Once all open file descriptors are closed and the device has been removed,
* the refcount of the device will fall to 0 and this will be called.
*/
static void telem_device_free(struct device *d)
{
struct telem_device_data *dev_data;
dev_data = container_of(d, struct telem_device_data, dev);
kfree(dev_data);
}
/**
* telem_device_probe() - Callback when creating a new device.
* @pdev: platform device that we will be receiving telems 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.
*
* Return: 0 on success, negative error code on failure.
*/
static int telem_device_probe(struct platform_device *pdev)
{
struct telem_device_data *dev_data;
int error, minor;
/* Get the next available device number */
minor = ida_alloc_max(&telem_ida, TELEM_MAX_DEV-1, GFP_KERNEL);
if (minor < 0) {
error = minor;
dev_err(&pdev->dev, "Failed to find minor number: %d", error);
return error;
}
dev_data = kzalloc(sizeof(*dev_data), GFP_KERNEL);
if (!dev_data) {
ida_simple_remove(&telem_ida, minor);
return -ENOMEM;
}
/* Initialize the device data */
dev_data->ec = dev_get_platdata(&pdev->dev);
atomic_set(&dev_data->available, 1);
platform_set_drvdata(pdev, dev_data);
/* Initialize the device */
dev_data->dev.devt = MKDEV(telem_major, minor);
dev_data->dev.class = &telem_class;
dev_data->dev.release = telem_device_free;
dev_set_name(&dev_data->dev, TELEM_DEV_NAME_FMT, minor);
device_initialize(&dev_data->dev);
/* Initialize the character device and add it to userspace */;
cdev_init(&dev_data->cdev, &telem_fops);
error = cdev_device_add(&dev_data->cdev, &dev_data->dev);
if (error) {
put_device(&dev_data->dev);
ida_simple_remove(&telem_ida, minor);
return error;
}
return 0;
}
static int telem_device_remove(struct platform_device *pdev)
{
struct telem_device_data *dev_data = platform_get_drvdata(pdev);
cdev_device_del(&dev_data->cdev, &dev_data->dev);
put_device(&dev_data->dev);
ida_simple_remove(&telem_ida, MINOR(dev_data->dev.devt));
return 0;
}
static struct platform_driver telem_driver = {
.probe = telem_device_probe,
.remove = telem_device_remove,
.driver = {
.name = DRV_NAME,
},
};
static int __init telem_module_init(void)
{
dev_t dev_num = 0;
int ret;
ret = class_register(&telem_class);
if (ret) {
pr_err(DRV_NAME ": Failed registering class: %d", ret);
return ret;
}
/* Request the kernel for device numbers, starting with minor=0 */
ret = alloc_chrdev_region(&dev_num, 0, TELEM_MAX_DEV, TELEM_DEV_NAME);
if (ret) {
pr_err(DRV_NAME ": Failed allocating dev numbers: %d", ret);
goto destroy_class;
}
telem_major = MAJOR(dev_num);
ret = platform_driver_register(&telem_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(telem_major, 0), TELEM_MAX_DEV);
destroy_class:
class_unregister(&telem_class);
ida_destroy(&telem_ida);
return ret;
}
static void __exit telem_module_exit(void)
{
platform_driver_unregister(&telem_driver);
unregister_chrdev_region(MKDEV(telem_major, 0), TELEM_MAX_DEV);
class_unregister(&telem_class);
ida_destroy(&telem_ida);
}
module_init(telem_module_init);
module_exit(telem_module_exit);
MODULE_AUTHOR("Nick Crews <ncrews@chromium.org>");
MODULE_DESCRIPTION("Wilco EC telemetry driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:" DRV_NAME);