i2c-stub.c

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/*
    i2c-stub.c - I2C/SMBus chip emulator

    Copyright (c) 2004 Mark M. Hoffman <[email protected]>
    Copyright (C) 2007, 2012 Jean Delvare <[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; 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
#define STUB_FUNC (I2C_FUNC_SMBUS_QUICK | I2C_FUNC_SMBUS_BYTE | \
           I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA | \
           I2C_FUNC_SMBUS_I2C_BLOCK)

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)");

static unsigned long functionality = STUB_FUNC;
module_param(functionality, ulong, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(functionality, "Override functionality bitfield");

struct stub_chip {
    u8 pointer;
    u16 words[256];     /* Byte operations use the LSB as per SMBus
                   specification */
};

static struct stub_chip *stub_chips;

/* Return negative errno 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, len;
    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->words[chip->pointer++] & 0xff;
            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->words[command] &= 0xff00;
            chip->words[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->words[command] & 0xff;
            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;

    case I2C_SMBUS_I2C_BLOCK_DATA:
        len = data->block[0];
        if (read_write == I2C_SMBUS_WRITE) {
            for (i = 0; i < len; i++) {
                chip->words[command + i] &= 0xff00;
                chip->words[command + i] |= data->block[1 + i];
            }
            dev_dbg(&adap->dev,
                "i2c block data - addr 0x%02x, wrote %d bytes at 0x%02x.\n",
                addr, len, command);
        } else {
            for (i = 0; i < len; i++) {
                data->block[1 + i] =
                    chip->words[command + i] & 0xff;
            }
            dev_dbg(&adap->dev,
                "i2c block data - addr 0x%02x, read  %d bytes at 0x%02x.\n",
                addr, len, command);
        }

        ret = 0;
        break;

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

    return ret;
}

static u32 stub_func(struct i2c_adapter *adapter)
{
    return STUB_FUNC & functionality;
}

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 | I2C_CLASS_SPD,
    .algo       = &smbus_algorithm,
    .name       = "SMBus stub driver",
};

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

    if (!chip_addr[0]) {
        pr_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) {
            pr_err("i2c-stub: Invalid chip address 0x%02x\n",
                   chip_addr[i]);
            return -EINVAL;
        }

        pr_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) {
        pr_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 <[email protected]>");
MODULE_DESCRIPTION("I2C stub driver");
MODULE_LICENSE("GPL");

module_init(i2c_stub_init);
module_exit(i2c_stub_exit);