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i2c-stub.c

/*
    i2c-stub.c - Part of lm_sensors, Linux kernel modules for hardware
              monitoring

    Copyright (c) 2004 Mark M. Hoffman <mhoffman@lightlink.com>

    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; either version 2 of the License, or
    (at your option) any later version.

    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.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#define DEBUG 1

#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/errno.h>
#include <linux/i2c.h>

#define MAX_CHIPS 10

static unsigned short chip_addr[MAX_CHIPS];
module_param_array(chip_addr, ushort, NULL, S_IRUGO);
MODULE_PARM_DESC(chip_addr,
             "Chip addresses (up to 10, between 0x03 and 0x77)\n");

struct stub_chip {
      u8 pointer;
      u8 bytes[256];
      u16 words[256];
};

static struct stub_chip *stub_chips;

/* Return -1 on error. */
static s32 stub_xfer(struct i2c_adapter * adap, u16 addr, unsigned short flags,
      char read_write, u8 command, int size, union i2c_smbus_data * data)
{
      s32 ret;
      int i;
      struct stub_chip *chip = NULL;

      /* Search for the right chip */
      for (i = 0; i < MAX_CHIPS && chip_addr[i]; i++) {
            if (addr == chip_addr[i]) {
                  chip = stub_chips + i;
                  break;
            }
      }
      if (!chip)
            return -ENODEV;

      switch (size) {

      case I2C_SMBUS_QUICK:
            dev_dbg(&adap->dev, "smbus quick - addr 0x%02x\n", addr);
            ret = 0;
            break;

      case I2C_SMBUS_BYTE:
            if (read_write == I2C_SMBUS_WRITE) {
                  chip->pointer = command;
                  dev_dbg(&adap->dev, "smbus byte - addr 0x%02x, "
                              "wrote 0x%02x.\n",
                              addr, command);
            } else {
                  data->byte = chip->bytes[chip->pointer++];
                  dev_dbg(&adap->dev, "smbus byte - addr 0x%02x, "
                              "read  0x%02x.\n",
                              addr, data->byte);
            }

            ret = 0;
            break;

      case I2C_SMBUS_BYTE_DATA:
            if (read_write == I2C_SMBUS_WRITE) {
                  chip->bytes[command] = data->byte;
                  dev_dbg(&adap->dev, "smbus byte data - addr 0x%02x, "
                              "wrote 0x%02x at 0x%02x.\n",
                              addr, data->byte, command);
            } else {
                  data->byte = chip->bytes[command];
                  dev_dbg(&adap->dev, "smbus byte data - addr 0x%02x, "
                              "read  0x%02x at 0x%02x.\n",
                              addr, data->byte, command);
            }
            chip->pointer = command + 1;

            ret = 0;
            break;

      case I2C_SMBUS_WORD_DATA:
            if (read_write == I2C_SMBUS_WRITE) {
                  chip->words[command] = data->word;
                  dev_dbg(&adap->dev, "smbus word data - addr 0x%02x, "
                              "wrote 0x%04x at 0x%02x.\n",
                              addr, data->word, command);
            } else {
                  data->word = chip->words[command];
                  dev_dbg(&adap->dev, "smbus word data - addr 0x%02x, "
                              "read  0x%04x at 0x%02x.\n",
                              addr, data->word, command);
            }

            ret = 0;
            break;

      default:
            dev_dbg(&adap->dev, "Unsupported I2C/SMBus command\n");
            ret = -1;
            break;
      } /* switch (size) */

      return ret;
}

static u32 stub_func(struct i2c_adapter *adapter)
{
      return I2C_FUNC_SMBUS_QUICK | I2C_FUNC_SMBUS_BYTE |
            I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA;
}

static const struct i2c_algorithm smbus_algorithm = {
      .functionality    = stub_func,
      .smbus_xfer = stub_xfer,
};

static struct i2c_adapter stub_adapter = {
      .owner            = THIS_MODULE,
      .class            = I2C_CLASS_HWMON,
      .algo       = &smbus_algorithm,
      .name       = "SMBus stub driver",
};

static int __init i2c_stub_init(void)
{
      int i, ret;

      if (!chip_addr[0]) {
            printk(KERN_ERR "i2c-stub: Please specify a chip address\n");
            return -ENODEV;
      }

      for (i = 0; i < MAX_CHIPS && chip_addr[i]; i++) {
            if (chip_addr[i] < 0x03 || chip_addr[i] > 0x77) {
                  printk(KERN_ERR "i2c-stub: Invalid chip address "
                         "0x%02x\n", chip_addr[i]);
                  return -EINVAL;
            }

            printk(KERN_INFO "i2c-stub: Virtual chip at 0x%02x\n",
                   chip_addr[i]);
      }

      /* Allocate memory for all chips at once */
      stub_chips = kzalloc(i * sizeof(struct stub_chip), GFP_KERNEL);
      if (!stub_chips) {
            printk(KERN_ERR "i2c-stub: Out of memory\n");
            return -ENOMEM;
      }

      ret = i2c_add_adapter(&stub_adapter);
      if (ret)
            kfree(stub_chips);
      return ret;
}

static void __exit i2c_stub_exit(void)
{
      i2c_del_adapter(&stub_adapter);
      kfree(stub_chips);
}

MODULE_AUTHOR("Mark M. Hoffman <mhoffman@lightlink.com>");
MODULE_DESCRIPTION("I2C stub driver");
MODULE_LICENSE("GPL");

module_init(i2c_stub_init);
module_exit(i2c_stub_exit);


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