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