/*
   * ChromeOS EC multi-function device (I2C)
   *
   * Copyright (C) 2012 Google, Inc
   *
   * This software is licensed under the terms of the GNU General Public
   * License version 2, as published by the Free Software Foundation, and
   * may be copied, distributed, and modified under those terms.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   */

  #include <linux/delay.h>

  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/i2c.h>
  #include <linux/interrupt.h>
  #include <linux/mfd/cros_ec.h>
  #include <linux/mfd/cros_ec_commands.h>
  #include <linux/platform_device.h>
  #include <linux/slab.h>

  /**
   * Request format for protocol v3
   * byte 0	0xda (EC_COMMAND_PROTOCOL_3)
   * byte 1-8	struct ec_host_request
   * byte 10-	response data
   */
  struct ec_host_request_i2c {
  	/* Always 0xda to backward compatible with v2 struct */
  	uint8_t  command_protocol;
  	struct ec_host_request ec_request;
  } __packed;
  
  
  /*
   * Response format for protocol v3
   * byte 0	result code
   * byte 1	packet_length
   * byte 2-9	struct ec_host_response
   * byte 10-	response data
   */
  struct ec_host_response_i2c {
  	uint8_t result;
  	uint8_t packet_length;
  	struct ec_host_response ec_response;
  } __packed;

  static inline struct cros_ec_device *to_ec_dev(struct device *dev)
  {
  	struct i2c_client *client = to_i2c_client(dev);
  
  	return i2c_get_clientdata(client);
  }

  static int cros_ec_pkt_xfer_i2c(struct cros_ec_device *ec_dev,
  				struct cros_ec_command *msg)
  {
  	struct i2c_client *client = ec_dev->priv;
  	int ret = -ENOMEM;
  	int i;
  	int packet_len;
  	u8 *out_buf = NULL;
  	u8 *in_buf = NULL;
  	u8 sum;
  	struct i2c_msg i2c_msg[2];
  	struct ec_host_response *ec_response;
  	struct ec_host_request_i2c *ec_request_i2c;
  	struct ec_host_response_i2c *ec_response_i2c;
  	int request_header_size = sizeof(struct ec_host_request_i2c);
  	int response_header_size = sizeof(struct ec_host_response_i2c);
  
  	i2c_msg[0].addr = client->addr;
  	i2c_msg[0].flags = 0;
  	i2c_msg[1].addr = client->addr;
  	i2c_msg[1].flags = I2C_M_RD;
  
  	packet_len = msg->insize + response_header_size;
  	BUG_ON(packet_len > ec_dev->din_size);
  	in_buf = ec_dev->din;
  	i2c_msg[1].len = packet_len;
  	i2c_msg[1].buf = (char *) in_buf;
  
  	packet_len = msg->outsize + request_header_size;
  	BUG_ON(packet_len > ec_dev->dout_size);
  	out_buf = ec_dev->dout;
  	i2c_msg[0].len = packet_len;
  	i2c_msg[0].buf = (char *) out_buf;
  
  	/* create request data */
  	ec_request_i2c = (struct ec_host_request_i2c *) out_buf;
  	ec_request_i2c->command_protocol = EC_COMMAND_PROTOCOL_3;
  
  	ec_dev->dout++;
  	ret = cros_ec_prepare_tx(ec_dev, msg);
  	ec_dev->dout--;
  
  	/* send command to EC and read answer */
  	ret = i2c_transfer(client->adapter, i2c_msg, 2);
  	if (ret < 0) {
  		dev_dbg(ec_dev->dev, "i2c transfer failed: %d
  ", ret);
  		goto done;
  	} else if (ret != 2) {
  		dev_err(ec_dev->dev, "failed to get response: %d
  ", ret);
  		ret = -EIO;
  		goto done;
  	}
  
  	ec_response_i2c = (struct ec_host_response_i2c *) in_buf;
  	msg->result = ec_response_i2c->result;
  	ec_response = &ec_response_i2c->ec_response;
  
  	switch (msg->result) {
  	case EC_RES_SUCCESS:
  		break;
  	case EC_RES_IN_PROGRESS:
  		ret = -EAGAIN;
  		dev_dbg(ec_dev->dev, "command 0x%02x in progress
  ",
  			msg->command);
  		goto done;
  
  	default:
  		dev_dbg(ec_dev->dev, "command 0x%02x returned %d
  ",
  			msg->command, msg->result);
  		/*
  		 * When we send v3 request to v2 ec, ec won't recognize the
  		 * 0xda (EC_COMMAND_PROTOCOL_3) and will return with status
  		 * EC_RES_INVALID_COMMAND with zero data length.
  		 *
  		 * In case of invalid command for v3 protocol the data length
  		 * will be at least sizeof(struct ec_host_response)
  		 */
  		if (ec_response_i2c->result == EC_RES_INVALID_COMMAND &&
  		    ec_response_i2c->packet_length == 0) {
  			ret = -EPROTONOSUPPORT;
  			goto done;
  		}
  	}
  
  	if (ec_response_i2c->packet_length < sizeof(struct ec_host_response)) {
  		dev_err(ec_dev->dev,
  			"response of %u bytes too short; not a full header
  ",
  			ec_response_i2c->packet_length);
  		ret = -EBADMSG;
  		goto done;
  	}
  
  	if (msg->insize < ec_response->data_len) {
  		dev_err(ec_dev->dev,
  			"response data size is too large: expected %u, got %u
  ",
  			msg->insize,
  			ec_response->data_len);
  		ret = -EMSGSIZE;
  		goto done;
  	}
  
  	/* copy response packet payload and compute checksum */
  	sum = 0;
  	for (i = 0; i < sizeof(struct ec_host_response); i++)
  		sum += ((u8 *)ec_response)[i];
  
  	memcpy(msg->data,
  	       in_buf + response_header_size,
  	       ec_response->data_len);
  	for (i = 0; i < ec_response->data_len; i++)
  		sum += msg->data[i];
  
  	/* All bytes should sum to zero */
  	if (sum) {
  		dev_err(ec_dev->dev, "bad packet checksum
  ");
  		ret = -EBADMSG;
  		goto done;
  	}
  
  	ret = ec_response->data_len;
  
  done:
  	if (msg->command == EC_CMD_REBOOT_EC)
  		msleep(EC_REBOOT_DELAY_MS);
  
  	return ret;
  }

  static int cros_ec_cmd_xfer_i2c(struct cros_ec_device *ec_dev,

  				struct cros_ec_command *msg)

  {
  	struct i2c_client *client = ec_dev->priv;
  	int ret = -ENOMEM;
  	int i;

  	int len;

  	int packet_len;
  	u8 *out_buf = NULL;
  	u8 *in_buf = NULL;
  	u8 sum;
  	struct i2c_msg i2c_msg[2];
  
  	i2c_msg[0].addr = client->addr;
  	i2c_msg[0].flags = 0;
  	i2c_msg[1].addr = client->addr;
  	i2c_msg[1].flags = I2C_M_RD;
  
  	/*
  	 * allocate larger packet (one byte for checksum, one byte for
  	 * length, and one for result code)
  	 */

  	packet_len = msg->insize + 3;

  	in_buf = kzalloc(packet_len, GFP_KERNEL);
  	if (!in_buf)
  		goto done;
  	i2c_msg[1].len = packet_len;
  	i2c_msg[1].buf = (char *)in_buf;
  
  	/*
  	 * allocate larger packet (one byte for checksum, one for
  	 * command code, one for length, and one for command version)
  	 */

  	packet_len = msg->outsize + 4;

  	out_buf = kzalloc(packet_len, GFP_KERNEL);
  	if (!out_buf)
  		goto done;
  	i2c_msg[0].len = packet_len;
  	i2c_msg[0].buf = (char *)out_buf;
  
  	out_buf[0] = EC_CMD_VERSION0 + msg->version;

  	out_buf[1] = msg->command;
  	out_buf[2] = msg->outsize;

  
  	/* copy message payload and compute checksum */
  	sum = out_buf[0] + out_buf[1] + out_buf[2];

  	for (i = 0; i < msg->outsize; i++) {

  		out_buf[3 + i] = msg->data[i];

  		sum += out_buf[3 + i];
  	}

  	out_buf[3 + msg->outsize] = sum;

  
  	/* send command to EC and read answer */
  	ret = i2c_transfer(client->adapter, i2c_msg, 2);
  	if (ret < 0) {
  		dev_err(ec_dev->dev, "i2c transfer failed: %d
  ", ret);
  		goto done;
  	} else if (ret != 2) {
  		dev_err(ec_dev->dev, "failed to get response: %d
  ", ret);
  		ret = -EIO;
  		goto done;
  	}
  
  	/* check response error code */

  	msg->result = i2c_msg[1].buf[0];
  	ret = cros_ec_check_result(ec_dev, msg);
  	if (ret)

  		goto done;

  	len = in_buf[1];
  	if (len > msg->insize) {
  		dev_err(ec_dev->dev, "packet too long (%d bytes, expected %d)",
  			len, msg->insize);
  		ret = -ENOSPC;
  		goto done;
  	}

  	/* copy response packet payload and compute checksum */
  	sum = in_buf[0] + in_buf[1];

  	for (i = 0; i < len; i++) {

  		msg->data[i] = in_buf[2 + i];

  		sum += in_buf[2 + i];
  	}
  	dev_dbg(ec_dev->dev, "packet: %*ph, sum = %02x
  ",
  		i2c_msg[1].len, in_buf, sum);

  	if (sum != in_buf[2 + len]) {

  		dev_err(ec_dev->dev, "bad packet checksum
  ");
  		ret = -EBADMSG;
  		goto done;
  	}

  	ret = len;

  done:

  	kfree(in_buf);
  	kfree(out_buf);

  	if (msg->command == EC_CMD_REBOOT_EC)
  		msleep(EC_REBOOT_DELAY_MS);

  	return ret;
  }

  static int cros_ec_i2c_probe(struct i2c_client *client,

  			     const struct i2c_device_id *dev_id)
  {
  	struct device *dev = &client->dev;
  	struct cros_ec_device *ec_dev = NULL;
  	int err;

  	ec_dev = devm_kzalloc(dev, sizeof(*ec_dev), GFP_KERNEL);

  	if (!ec_dev)
  		return -ENOMEM;
  
  	i2c_set_clientdata(client, ec_dev);

  	ec_dev->dev = dev;
  	ec_dev->priv = client;
  	ec_dev->irq = client->irq;

  	ec_dev->cmd_xfer = cros_ec_cmd_xfer_i2c;

  	ec_dev->pkt_xfer = cros_ec_pkt_xfer_i2c;

  	ec_dev->phys_name = client->adapter->name;

  	ec_dev->din_size = sizeof(struct ec_host_response_i2c) +

  			   sizeof(struct ec_response_get_protocol_info);

  	ec_dev->dout_size = sizeof(struct ec_host_request_i2c);

  
  	err = cros_ec_register(ec_dev);
  	if (err) {
  		dev_err(dev, "cannot register EC
  ");
  		return err;
  	}
  
  	return 0;
  }

  static int cros_ec_i2c_remove(struct i2c_client *client)

  {
  	struct cros_ec_device *ec_dev = i2c_get_clientdata(client);
  
  	cros_ec_remove(ec_dev);
  
  	return 0;
  }
  
  #ifdef CONFIG_PM_SLEEP
  static int cros_ec_i2c_suspend(struct device *dev)
  {
  	struct cros_ec_device *ec_dev = to_ec_dev(dev);
  
  	return cros_ec_suspend(ec_dev);
  }
  
  static int cros_ec_i2c_resume(struct device *dev)
  {
  	struct cros_ec_device *ec_dev = to_ec_dev(dev);
  
  	return cros_ec_resume(ec_dev);
  }
  #endif
  
  static SIMPLE_DEV_PM_OPS(cros_ec_i2c_pm_ops, cros_ec_i2c_suspend,
  			  cros_ec_i2c_resume);

  static const struct of_device_id cros_ec_i2c_of_match[] = {
  	{ .compatible = "google,cros-ec-i2c", },
  	{ /* sentinel */ },
  };
  MODULE_DEVICE_TABLE(of, cros_ec_i2c_of_match);

  static const struct i2c_device_id cros_ec_i2c_id[] = {
  	{ "cros-ec-i2c", 0 },
  	{ }
  };
  MODULE_DEVICE_TABLE(i2c, cros_ec_i2c_id);
  
  static struct i2c_driver cros_ec_driver = {
  	.driver	= {
  		.name	= "cros-ec-i2c",

  		.of_match_table = of_match_ptr(cros_ec_i2c_of_match),

  		.pm	= &cros_ec_i2c_pm_ops,
  	},

  	.probe		= cros_ec_i2c_probe,
  	.remove		= cros_ec_i2c_remove,

  	.id_table	= cros_ec_i2c_id,
  };
  
  module_i2c_driver(cros_ec_driver);
  
  MODULE_LICENSE("GPL");
  MODULE_DESCRIPTION("ChromeOS EC multi function device");