i2c-tiny-usb.c

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/*
 * driver for the i2c-tiny-usb adapter - 1.0
 * http://www.harbaum.org/till/i2c_tiny_usb
 *
 * Copyright (C) 2006-2007 Till Harbaum ([email protected])
 *
 * 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 status;
    struct i2c_msg *pmsg;
    int i;

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

    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");
                return -EREMOTEIO;
            }
        } 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");
                return -EREMOTEIO;
            }
        }

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

        dev_dbg(&adapter->dev, "  status = %d\n", status);
        if (status == STATUS_ADDRESS_NAK)
            return -EREMOTEIO;
    }

    return i;
}

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

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

    return le32_to_cpu(func);
}

/* 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 */
    { USB_DEVICE(0x1964, 0x0001) },   /* Robofuzz OSIF */
    { }                               /* 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;

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

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;

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

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 <[email protected]>");
MODULE_DESCRIPTION("i2c-tiny-usb driver v1.0");
MODULE_LICENSE("GPL");