/*
 * driver for the i2c-tiny-usb adapter - 1.0
 * http://www.harbaum.org/till/i2c_tiny_usb
 *
 * Copyright (C) 2006-2007 Till Harbaum (Till@Harbaum.org)
 *
 * 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/errno.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/types.h>

/* include interfaces to usb layer */
#include <linux/usb.h>

/* include interface to i2c layer */
#include <linux/i2c.h>

/* commands via USB, must match command ids in the firmware */
#define CMD_ECHO                0
#define CMD_GET_FUNC            1
#define CMD_SET_DELAY           2
#define CMD_GET_STATUS          3

#define CMD_I2C_IO              4
#define CMD_I2C_IO_BEGIN        (1<<0)
#define CMD_I2C_IO_END          (1<<1)

/* i2c bit delay, default is 10us -> 100kHz max
   (in practice, due to additional delays in the i2c bitbanging
   code this results in a i2c clock of about 50kHz) */
static unsigned short delay = 10;
module_param(delay, ushort, 0);
MODULE_PARM_DESC(delay, "bit delay in microseconds "
                 "(default is 10us for 100kHz max)");

static int usb_read(struct i2c_adapter *adapter, int cmd,
                    int value, int index, void *data, int len);

static int usb_write(struct i2c_adapter *adapter, int cmd,
                     int value, int index, void *data, int len);

/* ----- begin of i2c layer ---------------------------------------------- */

#define STATUS_IDLE             0
#define STATUS_ADDRESS_ACK      1
#define STATUS_ADDRESS_NAK      2

static int usb_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num)
{
        unsigned char *pstatus;
        struct i2c_msg *pmsg;
        int i, ret;

        dev_dbg(&adapter->dev, "master xfer %d messages:\n", num);

        pstatus = kmalloc(sizeof(*pstatus), GFP_KERNEL);
        if (!pstatus)
                return -ENOMEM;

        for (i = 0 ; i < num ; i++) {
                int cmd = CMD_I2C_IO;

                if (i == 0)
                        cmd |= CMD_I2C_IO_BEGIN;

                if (i == num-1)
                        cmd |= CMD_I2C_IO_END;

                pmsg = &msgs[i];

                dev_dbg(&adapter->dev,
                        "  %d: %s (flags %d) %d bytes to 0x%02x\n",
                        i, pmsg->flags & I2C_M_RD ? "read" : "write",
                        pmsg->flags, pmsg->len, pmsg->addr);

                /* and directly send the message */
                if (pmsg->flags & I2C_M_RD) {
                        /* read data */
                        if (usb_read(adapter, cmd,
                                     pmsg->flags, pmsg->addr,
                                     pmsg->buf, pmsg->len) != pmsg->len) {
                                dev_err(&adapter->dev,
                                        "failure reading data\n");
                                ret = -EREMOTEIO;
                                goto out;
                        }
                } else {
                        /* write data */
                        if (usb_write(adapter, cmd,
                                      pmsg->flags, pmsg->addr,
                                      pmsg->buf, pmsg->len) != pmsg->len) {
                                dev_err(&adapter->dev,
                                        "failure writing data\n");
                                ret = -EREMOTEIO;
                                goto out;
                        }
                }

                /* read status */
                if (usb_read(adapter, CMD_GET_STATUS, 0, 0, pstatus, 1) != 1) {
                        dev_err(&adapter->dev, "failure reading status\n");
                        ret = -EREMOTEIO;
                        goto out;
                }

                dev_dbg(&adapter->dev, "  status = %d\n", *pstatus);
                if (*pstatus == STATUS_ADDRESS_NAK) {
                        ret = -EREMOTEIO;
                        goto out;
                }
        }

        ret = i;
out:
        kfree(pstatus);
        return ret;
}

static u32 usb_func(struct i2c_adapter *adapter)
{
        __le32 *pfunc;
        u32 ret;

        pfunc = kmalloc(sizeof(*pfunc), GFP_KERNEL);

        /* get functionality from adapter */
        if (!pfunc || usb_read(adapter, CMD_GET_FUNC, 0, 0, pfunc,
                               sizeof(*pfunc)) != sizeof(*pfunc)) {
                dev_err(&adapter->dev, "failure reading functionality\n");
                ret = 0;
                goto out;
        }

        ret = le32_to_cpup(pfunc);
out:
        kfree(pfunc);
        return ret;
}

/* This is the actual algorithm we define */
static const struct i2c_algorithm usb_algorithm = {
        .master_xfer    = usb_xfer,
        .functionality  = usb_func,
};

/* ----- end of i2c layer ------------------------------------------------ */

/* ----- begin of usb layer ---------------------------------------------- */

/*
 * Initially the usb i2c interface uses a vid/pid pair donated by
 * Future Technology Devices International Ltd., later a pair was
 * bought from EZPrototypes
 */
static const struct usb_device_id i2c_tiny_usb_table[] = {
        { USB_DEVICE(0x0403, 0xc631) },   /* FTDI */
        { USB_DEVICE(0x1c40, 0x0534) },   /* EZPrototypes */
        { }                               /* Terminating entry */
};

MODULE_DEVICE_TABLE(usb, i2c_tiny_usb_table);

/* Structure to hold all of our device specific stuff */
struct i2c_tiny_usb {
        struct usb_device *usb_dev; /* the usb device for this device */
        struct usb_interface *interface; /* the interface for this device */
        struct i2c_adapter adapter; /* i2c related things */
};

static int usb_read(struct i2c_adapter *adapter, int cmd,
                    int value, int index, void *data, int len)
{
        struct i2c_tiny_usb *dev = (struct i2c_tiny_usb *)adapter->algo_data;
        void *dmadata = kmalloc(len, GFP_KERNEL);
        int ret;

        if (!dmadata)
                return -ENOMEM;

        /* do control transfer */
        ret = usb_control_msg(dev->usb_dev, usb_rcvctrlpipe(dev->usb_dev, 0),
                               cmd, USB_TYPE_VENDOR | USB_RECIP_INTERFACE |
                               USB_DIR_IN, value, index, dmadata, len, 2000);

        memcpy(data, dmadata, len);
        kfree(dmadata);
        return ret;
}

static int usb_write(struct i2c_adapter *adapter, int cmd,
                     int value, int index, void *data, int len)
{
        struct i2c_tiny_usb *dev = (struct i2c_tiny_usb *)adapter->algo_data;
        void *dmadata = kmemdup(data, len, GFP_KERNEL);
        int ret;

        if (!dmadata)
                return -ENOMEM;

        /* do control transfer */
        ret = usb_control_msg(dev->usb_dev, usb_sndctrlpipe(dev->usb_dev, 0),
                               cmd, USB_TYPE_VENDOR | USB_RECIP_INTERFACE,
                               value, index, dmadata, len, 2000);

        kfree(dmadata);
        return ret;
}

static void i2c_tiny_usb_free(struct i2c_tiny_usb *dev)
{
        usb_put_dev(dev->usb_dev);
        kfree(dev);
}

static int i2c_tiny_usb_probe(struct usb_interface *interface,
                              const struct usb_device_id *id)
{
        struct i2c_tiny_usb *dev;
        int retval = -ENOMEM;
        u16 version;

        dev_dbg(&interface->dev, "probing usb device\n");

        /* allocate memory for our device state and initialize it */
        dev = kzalloc(sizeof(*dev), GFP_KERNEL);
        if (dev == NULL) {
                dev_err(&interface->dev, "Out of memory\n");
                goto error;
        }

        dev->usb_dev = usb_get_dev(interface_to_usbdev(interface));
        dev->interface = interface;

        /* save our data pointer in this interface device */
        usb_set_intfdata(interface, dev);

        version = le16_to_cpu(dev->usb_dev->descriptor.bcdDevice);
        dev_info(&interface->dev,
                 "version %x.%02x found at bus %03d address %03d\n",
                 version >> 8, version & 0xff,
                 dev->usb_dev->bus->busnum, dev->usb_dev->devnum);

        /* setup i2c adapter description */
        dev->adapter.owner = THIS_MODULE;
        dev->adapter.class = I2C_CLASS_HWMON;
        dev->adapter.algo = &usb_algorithm;
        dev->adapter.algo_data = dev;
        snprintf(dev->adapter.name, sizeof(dev->adapter.name),
                 "i2c-tiny-usb at bus %03d device %03d",
                 dev->usb_dev->bus->busnum, dev->usb_dev->devnum);

        if (usb_write(&dev->adapter, CMD_SET_DELAY, delay, 0, NULL, 0) != 0) {
                dev_err(&dev->adapter.dev,
                        "failure setting delay to %dus\n", delay);
                retval = -EIO;
                goto error;
        }

        dev->adapter.dev.parent = &dev->interface->dev;

        /* and finally attach to i2c layer */
        i2c_add_adapter(&dev->adapter);

        /* inform user about successful attachment to i2c layer */
        dev_info(&dev->adapter.dev, "connected i2c-tiny-usb device\n");

        return 0;

 error:
        if (dev)
                i2c_tiny_usb_free(dev);

        return retval;
}

static void i2c_tiny_usb_disconnect(struct usb_interface *interface)
{
        struct i2c_tiny_usb *dev = usb_get_intfdata(interface);

        i2c_del_adapter(&dev->adapter);
        usb_set_intfdata(interface, NULL);
        i2c_tiny_usb_free(dev);

        dev_dbg(&interface->dev, "disconnected\n");
}

static struct usb_driver i2c_tiny_usb_driver = {
        .name           = "i2c-tiny-usb",
        .probe          = i2c_tiny_usb_probe,
        .disconnect     = i2c_tiny_usb_disconnect,
        .id_table       = i2c_tiny_usb_table,
};

module_usb_driver(i2c_tiny_usb_driver);

/* ----- end of usb layer ------------------------------------------------ */

MODULE_AUTHOR("Till Harbaum <Till@Harbaum.org>");
MODULE_DESCRIPTION("i2c-tiny-usb driver v1.0");
MODULE_LICENSE("GPL");