--- /dev/null
+// 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 whitelisted 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 TELEM_ARGS_SIZE_MAX 30
+
+/**
+ * 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;
+ u8 args[TELEM_ARGS_SIZE_MAX];
+} __packed;
+
+/*
+ * 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;
+
+/**
+ * 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 whitelisted 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(struct telem_args_get_log);
+ break;
+ case WILCO_EC_TELEM_GET_VERSION:
+ max_size += sizeof(struct telem_args_get_version);
+ break;
+ case WILCO_EC_TELEM_GET_FAN_INFO:
+ max_size += sizeof(struct telem_args_get_fan_info);
+ break;
+ case WILCO_EC_TELEM_GET_DIAG_INFO:
+ max_size += sizeof(struct telem_args_get_diag_info);
+ break;
+ case WILCO_EC_TELEM_GET_TEMP_INFO:
+ max_size += sizeof(struct telem_args_get_temp_info);
+ break;
+ case WILCO_EC_TELEM_GET_TEMP_READ:
+ max_size += sizeof(struct telem_args_get_temp_read);
+ break;
+ case WILCO_EC_TELEM_GET_BATT_EXT_INFO:
+ max_size += sizeof(struct telem_args_get_batt_ext_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;
+ 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);
projects / platform / kernel / linux-rpi.git / commitdiff