/*
   * Driver for the Diolan DLN-2 USB-I2C adapter
   *
   * Copyright (c) 2014 Intel Corporation
   *
   * Derived from:
   *  i2c-diolan-u2c.c
   *  Copyright (c) 2010-2011 Ericsson AB
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public License as
   * published by the Free Software Foundation, version 2.
   */
  
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/types.h>
  #include <linux/slab.h>
  #include <linux/i2c.h>
  #include <linux/platform_device.h>
  #include <linux/mfd/dln2.h>
  
  #define DLN2_I2C_MODULE_ID		0x03
  #define DLN2_I2C_CMD(cmd)		DLN2_CMD(cmd, DLN2_I2C_MODULE_ID)
  
  /* I2C commands */
  #define DLN2_I2C_GET_PORT_COUNT		DLN2_I2C_CMD(0x00)
  #define DLN2_I2C_ENABLE			DLN2_I2C_CMD(0x01)
  #define DLN2_I2C_DISABLE		DLN2_I2C_CMD(0x02)
  #define DLN2_I2C_IS_ENABLED		DLN2_I2C_CMD(0x03)
  #define DLN2_I2C_WRITE			DLN2_I2C_CMD(0x06)
  #define DLN2_I2C_READ			DLN2_I2C_CMD(0x07)
  #define DLN2_I2C_SCAN_DEVICES		DLN2_I2C_CMD(0x08)
  #define DLN2_I2C_PULLUP_ENABLE		DLN2_I2C_CMD(0x09)
  #define DLN2_I2C_PULLUP_DISABLE		DLN2_I2C_CMD(0x0A)
  #define DLN2_I2C_PULLUP_IS_ENABLED	DLN2_I2C_CMD(0x0B)
  #define DLN2_I2C_TRANSFER		DLN2_I2C_CMD(0x0C)
  #define DLN2_I2C_SET_MAX_REPLY_COUNT	DLN2_I2C_CMD(0x0D)
  #define DLN2_I2C_GET_MAX_REPLY_COUNT	DLN2_I2C_CMD(0x0E)
  
  #define DLN2_I2C_MAX_XFER_SIZE		256
  #define DLN2_I2C_BUF_SIZE		(DLN2_I2C_MAX_XFER_SIZE + 16)
  
  struct dln2_i2c {
  	struct platform_device *pdev;
  	struct i2c_adapter adapter;
  	u8 port;
  	/*
  	 * Buffer to hold the packet for read or write transfers. One is enough
  	 * since we can't have multiple transfers in parallel on the i2c bus.
  	 */
  	void *buf;
  };
  
  static int dln2_i2c_enable(struct dln2_i2c *dln2, bool enable)
  {
  	u16 cmd;
  	struct {
  		u8 port;
  	} tx;
  
  	tx.port = dln2->port;
  
  	if (enable)
  		cmd = DLN2_I2C_ENABLE;
  	else
  		cmd = DLN2_I2C_DISABLE;
  
  	return dln2_transfer_tx(dln2->pdev, cmd, &tx, sizeof(tx));
  }
  
  static int dln2_i2c_write(struct dln2_i2c *dln2, u8 addr,
  			  u8 *data, u16 data_len)
  {
  	int ret;
  	struct {
  		u8 port;
  		u8 addr;
  		u8 mem_addr_len;
  		__le32 mem_addr;
  		__le16 buf_len;
  		u8 buf[DLN2_I2C_MAX_XFER_SIZE];
  	} __packed *tx = dln2->buf;
  	unsigned len;
  
  	BUILD_BUG_ON(sizeof(*tx) > DLN2_I2C_BUF_SIZE);
  
  	tx->port = dln2->port;
  	tx->addr = addr;
  	tx->mem_addr_len = 0;
  	tx->mem_addr = 0;
  	tx->buf_len = cpu_to_le16(data_len);
  	memcpy(tx->buf, data, data_len);
  
  	len = sizeof(*tx) + data_len - DLN2_I2C_MAX_XFER_SIZE;
  	ret = dln2_transfer_tx(dln2->pdev, DLN2_I2C_WRITE, tx, len);
  	if (ret < 0)
  		return ret;
  
  	return data_len;
  }
  
  static int dln2_i2c_read(struct dln2_i2c *dln2, u16 addr, u8 *data,
  			 u16 data_len)
  {
  	int ret;
  	struct {
  		u8 port;
  		u8 addr;
  		u8 mem_addr_len;
  		__le32 mem_addr;
  		__le16 buf_len;
  	} __packed tx;
  	struct {
  		__le16 buf_len;
  		u8 buf[DLN2_I2C_MAX_XFER_SIZE];
  	} __packed *rx = dln2->buf;
  	unsigned rx_len = sizeof(*rx);
  
  	BUILD_BUG_ON(sizeof(*rx) > DLN2_I2C_BUF_SIZE);
  
  	tx.port = dln2->port;
  	tx.addr = addr;
  	tx.mem_addr_len = 0;
  	tx.mem_addr = 0;
  	tx.buf_len = cpu_to_le16(data_len);
  
  	ret = dln2_transfer(dln2->pdev, DLN2_I2C_READ, &tx, sizeof(tx),
  			    rx, &rx_len);
  	if (ret < 0)
  		return ret;
  	if (rx_len < sizeof(rx->buf_len) + data_len)
  		return -EPROTO;
  	if (le16_to_cpu(rx->buf_len) != data_len)
  		return -EPROTO;
  
  	memcpy(data, rx->buf, data_len);
  
  	return data_len;
  }
  
  static int dln2_i2c_xfer(struct i2c_adapter *adapter,
  			 struct i2c_msg *msgs, int num)
  {
  	struct dln2_i2c *dln2 = i2c_get_adapdata(adapter);
  	struct i2c_msg *pmsg;
  	int i;
  
  	for (i = 0; i < num; i++) {
  		int ret;
  
  		pmsg = &msgs[i];
  
  		if (pmsg->flags & I2C_M_RD) {
  			ret = dln2_i2c_read(dln2, pmsg->addr, pmsg->buf,
  					    pmsg->len);
  			if (ret < 0)
  				return ret;
  
  			pmsg->len = ret;
  		} else {
  			ret = dln2_i2c_write(dln2, pmsg->addr, pmsg->buf,
  					     pmsg->len);
  			if (ret != pmsg->len)
  				return -EPROTO;
  		}
  	}
  
  	return num;
  }
  
  static u32 dln2_i2c_func(struct i2c_adapter *a)
  {
  	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_BYTE | I2C_FUNC_SMBUS_BYTE_DATA |
  		I2C_FUNC_SMBUS_WORD_DATA | I2C_FUNC_SMBUS_BLOCK_PROC_CALL |
  		I2C_FUNC_SMBUS_I2C_BLOCK;
  }
  
  static const struct i2c_algorithm dln2_i2c_usb_algorithm = {
  	.master_xfer = dln2_i2c_xfer,
  	.functionality = dln2_i2c_func,
  };
  
  static struct i2c_adapter_quirks dln2_i2c_quirks = {
  	.max_read_len = DLN2_I2C_MAX_XFER_SIZE,
  	.max_write_len = DLN2_I2C_MAX_XFER_SIZE,
  };
  
  static int dln2_i2c_probe(struct platform_device *pdev)
  {
  	int ret;
  	struct dln2_i2c *dln2;
  	struct device *dev = &pdev->dev;
  	struct dln2_platform_data *pdata = dev_get_platdata(&pdev->dev);
  
  	dln2 = devm_kzalloc(dev, sizeof(*dln2), GFP_KERNEL);
  	if (!dln2)
  		return -ENOMEM;
  
  	dln2->buf = devm_kmalloc(dev, DLN2_I2C_BUF_SIZE, GFP_KERNEL);
  	if (!dln2->buf)
  		return -ENOMEM;
  
  	dln2->pdev = pdev;
  	dln2->port = pdata->port;
  
  	/* setup i2c adapter description */
  	dln2->adapter.owner = THIS_MODULE;
  	dln2->adapter.class = I2C_CLASS_HWMON;
  	dln2->adapter.algo = &dln2_i2c_usb_algorithm;
  	dln2->adapter.quirks = &dln2_i2c_quirks;
  	dln2->adapter.dev.parent = dev;
  	dln2->adapter.dev.of_node = dev->of_node;
  	i2c_set_adapdata(&dln2->adapter, dln2);
  	snprintf(dln2->adapter.name, sizeof(dln2->adapter.name), "%s-%s-%d",
  		 "dln2-i2c", dev_name(pdev->dev.parent), dln2->port);
  
  	platform_set_drvdata(pdev, dln2);
  
  	/* initialize the i2c interface */
  	ret = dln2_i2c_enable(dln2, true);
  	if (ret < 0) {
  		dev_err(dev, "failed to initialize adapter: %d
  ", ret);
  		return ret;
  	}
  
  	/* and finally attach to i2c layer */
  	ret = i2c_add_adapter(&dln2->adapter);
  	if (ret < 0) {
  		dev_err(dev, "failed to add I2C adapter: %d
  ", ret);
  		goto out_disable;
  	}
  
  	return 0;
  
  out_disable:
  	dln2_i2c_enable(dln2, false);
  
  	return ret;
  }
  
  static int dln2_i2c_remove(struct platform_device *pdev)
  {
  	struct dln2_i2c *dln2 = platform_get_drvdata(pdev);
  
  	i2c_del_adapter(&dln2->adapter);
  	dln2_i2c_enable(dln2, false);
  
  	return 0;
  }
  
  static struct platform_driver dln2_i2c_driver = {
  	.driver.name	= "dln2-i2c",
  	.probe		= dln2_i2c_probe,
  	.remove		= dln2_i2c_remove,
  };
  
  module_platform_driver(dln2_i2c_driver);
  
  MODULE_AUTHOR("Laurentiu Palcu <laurentiu.palcu@intel.com>");
  MODULE_DESCRIPTION("Driver for the Diolan DLN2 I2C master interface");
  MODULE_LICENSE("GPL v2");
  MODULE_ALIAS("platform:dln2-i2c");