linux/drivers/platform/chrome/wilco_ec/mailbox.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Mailbox interface for Wilco Embedded Controller
 *
 * Copyright 2018 Google LLC
 *
 * The Wilco EC is similar to a typical ChromeOS embedded controller.
 * It uses the same MEC based low-level communication and a similar
 * protocol, but with some important differences.  The EC firmware does
 * not support the same mailbox commands so it is not registered as a
 * cros_ec device type.
 *
 * Most messages follow a standard format, but there are some exceptions
 * and an interface is provided to do direct/raw transactions that do not
 * make assumptions about byte placement.
 */

#include <linux/delay.h>
#include <linux/device.h>
#include <linux/io.h>
#include <linux/platform_data/wilco-ec.h>
#include <linux/platform_device.h>

#include "../cros_ec_lpc_mec.h"

/* Version of mailbox interface */
#define EC_MAILBOX_VERSION …

/* Command to start mailbox transaction */
#define EC_MAILBOX_START_COMMAND …

/* Version of EC protocol */
#define EC_MAILBOX_PROTO_VERSION …

/* Number of header bytes to be counted as data bytes */
#define EC_MAILBOX_DATA_EXTRA …

/* Maximum timeout */
#define EC_MAILBOX_TIMEOUT …

/* EC response flags */
#define EC_CMDR_DATA …
#define EC_CMDR_PENDING …
#define EC_CMDR_BUSY …
#define EC_CMDR_CMD …

/**
 * wilco_ec_response_timed_out() - Wait for EC response.
 * @ec: EC device.
 *
 * Return: true if EC timed out, false if EC did not time out.
 */
static bool wilco_ec_response_timed_out(struct wilco_ec_device *ec)
{ … }

/**
 * wilco_ec_checksum() - Compute 8-bit checksum over data range.
 * @data: Data to checksum.
 * @size: Number of bytes to checksum.
 *
 * Return: 8-bit checksum of provided data.
 */
static u8 wilco_ec_checksum(const void *data, size_t size)
{ … }

/**
 * wilco_ec_prepare() - Prepare the request structure for the EC.
 * @msg: EC message with request information.
 * @rq: EC request structure to fill.
 */
static void wilco_ec_prepare(struct wilco_ec_message *msg,
			     struct wilco_ec_request *rq)
{ … }

/**
 * wilco_ec_transfer() - Perform actual data transfer.
 * @ec: EC device.
 * @msg: EC message data for request and response.
 * @rq: Filled in request structure
 *
 * Context: ec->mailbox_lock should be held while using this function.
 * Return: number of bytes received or negative error code on failure.
 */
static int wilco_ec_transfer(struct wilco_ec_device *ec,
			     struct wilco_ec_message *msg,
			     struct wilco_ec_request *rq)
{ … }

/**
 * wilco_ec_mailbox() - Send EC request and receive EC response.
 * @ec: EC device.
 * @msg: EC message data for request and response.
 *
 * On entry msg->type, msg->request_size, and msg->request_data should all be
 * filled in. If desired, msg->flags can be set.
 *
 * If a response is expected, msg->response_size should be set, and
 * msg->response_data should point to a buffer with enough space. On exit
 * msg->response_data will be filled.
 *
 * Return: number of bytes received or negative error code on failure.
 */
int wilco_ec_mailbox(struct wilco_ec_device *ec, struct wilco_ec_message *msg)
{ … }
EXPORT_SYMBOL_GPL(…);