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![Nick Crews](/assets/img/avatar_default.png)
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. Signed-off-by: Nick Crews <ncrews@chromium.org> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
206 lines
6.4 KiB
C
206 lines
6.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* ChromeOS Wilco Embedded Controller
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*
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* Copyright 2018 Google LLC
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*/
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#ifndef WILCO_EC_H
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#define WILCO_EC_H
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#include <linux/device.h>
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#include <linux/kernel.h>
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/* Message flags for using the mailbox() interface */
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#define WILCO_EC_FLAG_NO_RESPONSE BIT(0) /* EC does not respond */
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/* Normal commands have a maximum 32 bytes of data */
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#define EC_MAILBOX_DATA_SIZE 32
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/**
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* struct wilco_ec_device - Wilco Embedded Controller handle.
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* @dev: Device handle.
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* @mailbox_lock: Mutex to ensure one mailbox command at a time.
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* @io_command: I/O port for mailbox command. Provided by ACPI.
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* @io_data: I/O port for mailbox data. Provided by ACPI.
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* @io_packet: I/O port for mailbox packet data. Provided by ACPI.
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* @data_buffer: Buffer used for EC communication. The same buffer
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* is used to hold the request and the response.
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* @data_size: Size of the data buffer used for EC communication.
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* @debugfs_pdev: The child platform_device used by the debugfs sub-driver.
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* @rtc_pdev: The child platform_device used by the RTC sub-driver.
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* @telem_pdev: The child platform_device used by the telemetry sub-driver.
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*/
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struct wilco_ec_device {
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struct device *dev;
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struct mutex mailbox_lock;
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struct resource *io_command;
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struct resource *io_data;
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struct resource *io_packet;
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void *data_buffer;
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size_t data_size;
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struct platform_device *debugfs_pdev;
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struct platform_device *rtc_pdev;
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struct platform_device *telem_pdev;
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};
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/**
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* struct wilco_ec_request - Mailbox request message format.
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* @struct_version: Should be %EC_MAILBOX_PROTO_VERSION
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* @checksum: Sum of all bytes must be 0.
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* @mailbox_id: Mailbox identifier, specifies the command set.
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* @mailbox_version: Mailbox interface version %EC_MAILBOX_VERSION
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* @reserved: Set to zero.
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* @data_size: Length of following data.
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*/
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struct wilco_ec_request {
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u8 struct_version;
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u8 checksum;
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u16 mailbox_id;
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u8 mailbox_version;
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u8 reserved;
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u16 data_size;
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} __packed;
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/**
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* struct wilco_ec_response - Mailbox response message format.
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* @struct_version: Should be %EC_MAILBOX_PROTO_VERSION
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* @checksum: Sum of all bytes must be 0.
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* @result: Result code from the EC. Non-zero indicates an error.
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* @data_size: Length of the response data buffer.
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* @reserved: Set to zero.
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* @data: Response data buffer. Max size is %EC_MAILBOX_DATA_SIZE_EXTENDED.
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*/
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struct wilco_ec_response {
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u8 struct_version;
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u8 checksum;
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u16 result;
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u16 data_size;
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u8 reserved[2];
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u8 data[0];
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} __packed;
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/**
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* enum wilco_ec_msg_type - Message type to select a set of command codes.
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* @WILCO_EC_MSG_LEGACY: Legacy EC messages for standard EC behavior.
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* @WILCO_EC_MSG_PROPERTY: Get/Set/Sync EC controlled NVRAM property.
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* @WILCO_EC_MSG_TELEMETRY: Request telemetry data from the EC.
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*/
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enum wilco_ec_msg_type {
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WILCO_EC_MSG_LEGACY = 0x00f0,
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WILCO_EC_MSG_PROPERTY = 0x00f2,
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WILCO_EC_MSG_TELEMETRY = 0x00f5,
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};
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/**
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* struct wilco_ec_message - Request and response message.
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* @type: Mailbox message type.
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* @flags: Message flags, e.g. %WILCO_EC_FLAG_NO_RESPONSE.
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* @request_size: Number of bytes to send to the EC.
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* @request_data: Buffer containing the request data.
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* @response_size: Number of bytes to read from EC.
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* @response_data: Buffer containing the response data, should be
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* response_size bytes and allocated by caller.
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*/
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struct wilco_ec_message {
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enum wilco_ec_msg_type type;
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u8 flags;
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size_t request_size;
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void *request_data;
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size_t response_size;
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void *response_data;
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};
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/**
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* wilco_ec_mailbox() - Send request to the EC and receive the response.
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* @ec: Wilco EC device.
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* @msg: Wilco EC message.
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*
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* Return: Number of bytes received or negative error code on failure.
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*/
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int wilco_ec_mailbox(struct wilco_ec_device *ec, struct wilco_ec_message *msg);
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/*
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* A Property is typically a data item that is stored to NVRAM
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* by the EC. Each of these data items has an index associated
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* with it, known as the Property ID (PID). Properties may have
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* variable lengths, up to a max of WILCO_EC_PROPERTY_MAX_SIZE
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* bytes. Properties can be simple integers, or they may be more
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* complex binary data.
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*/
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#define WILCO_EC_PROPERTY_MAX_SIZE 4
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/**
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* struct ec_property_set_msg - Message to get or set a property.
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* @property_id: Which property to get or set.
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* @length: Number of bytes of |data| that are used.
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* @data: Actual property data.
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*/
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struct wilco_ec_property_msg {
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u32 property_id;
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int length;
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u8 data[WILCO_EC_PROPERTY_MAX_SIZE];
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};
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/**
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* wilco_ec_get_property() - Retrieve a property from the EC.
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* @ec: Embedded Controller device.
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* @prop_msg: Message for request and response.
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*
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* The property_id field of |prop_msg| should be filled before calling this
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* function. The result will be stored in the data and length fields.
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*
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* Return: 0 on success, negative error code on failure.
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*/
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int wilco_ec_get_property(struct wilco_ec_device *ec,
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struct wilco_ec_property_msg *prop_msg);
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/**
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* wilco_ec_set_property() - Store a property on the EC.
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* @ec: Embedded Controller device.
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* @prop_msg: Message for request and response.
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*
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* The property_id, length, and data fields of |prop_msg| should be
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* filled before calling this function.
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*
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* Return: 0 on success, negative error code on failure.
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*/
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int wilco_ec_set_property(struct wilco_ec_device *ec,
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struct wilco_ec_property_msg *prop_msg);
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/**
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* wilco_ec_get_byte_property() - Retrieve a byte-size property from the EC.
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* @ec: Embedded Controller device.
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* @property_id: Which property to retrieve.
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* @val: The result value, will be filled by this function.
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*
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* Return: 0 on success, negative error code on failure.
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*/
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int wilco_ec_get_byte_property(struct wilco_ec_device *ec, u32 property_id,
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u8 *val);
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/**
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* wilco_ec_get_byte_property() - Store a byte-size property on the EC.
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* @ec: Embedded Controller device.
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* @property_id: Which property to store.
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* @val: Value to store.
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*
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* Return: 0 on success, negative error code on failure.
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*/
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int wilco_ec_set_byte_property(struct wilco_ec_device *ec, u32 property_id,
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u8 val);
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/**
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* wilco_ec_add_sysfs() - Create sysfs entries
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* @ec: Wilco EC device
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*
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* wilco_ec_remove_sysfs() needs to be called afterwards
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* to perform the necessary cleanup.
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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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int wilco_ec_add_sysfs(struct wilco_ec_device *ec);
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void wilco_ec_remove_sysfs(struct wilco_ec_device *ec);
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#endif /* WILCO_EC_H */
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