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/*
* This handles incoming commands and provides responses.
*
* Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*
* EC <--> AP message handling.
*/
#include "board.h"
#include "message.h"
#include "keyboard_scan.h"
#include "util.h"
/* EC ID */
/* (TODO(dhendrix): Define this in board-specific code */
static const char ec_id[] = "Google Chrome EC";
/* Protocol version (least significant byte in lowest byte position) */
static const uint8_t proto_ver[] = { 1, 0, 0, 0 };
/**
* Get the response to a given command
*
* @param cmd Command byte to respond to
* @param buffp Buffer to use for data, or it can be updated to
* point to a new buffer
* @param max_len Number of bytes free at *buffp for the response.
* If the supplied buffer is used, this size must not
* be exceeded.
* @return number of bytes in response (which is in *buffp), or -1 on error
*/
static int message_get_response(int cmd, uint8_t **buffp, int max_len)
{
/*
* Invalid commands are ignored, just returning a stream of 0xff
* bytes.
*/
switch (cmd) {
case CMDC_PROTO_VER:
*buffp = (uint8_t *)proto_ver;
return sizeof(proto_ver);
case CMDC_NOP:
return 0;
case CMDC_ID:
*buffp = (char *)ec_id;
return sizeof(ec_id) - 1;
case CMDC_KEY_STATE:
return keyboard_get_scan(buffp, max_len);
default:
return -1;
}
return 0;
}
int message_process_cmd(int cmd, uint8_t *out_msg, int max_len)
{
uint8_t *msg;
int msg_len;
int need_copy;
int sum = 0;
int i;
msg = out_msg;
msg_len = message_get_response(cmd, &msg, max_len - MSG_PROTO_BYTES);
if (msg_len < 0)
return msg_len;
/*
* We add MSG_PROTO_BYTES bytes of overhead: truncate the reply
* if needed.
*/
if (msg_len + MSG_PROTO_BYTES > max_len)
msg_len = max_len - MSG_PROTO_BYTES;
ASSERT(msg_len >= 0 && msg_len < 0xffff);
need_copy = msg != out_msg;
ASSERT(!need_copy ||
msg + msg_len < out_msg ||
msg > out_msg + sizeof(out_msg));
for (i = 0; i < msg_len; i++) {
if (need_copy)
out_msg[i] = msg[i];
sum += msg[i];
}
out_msg[i] = sum;
return msg_len + MSG_PROTO_BYTES;
}
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