ttpci-eeprom.c

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/*
    Retrieve encoded MAC address from 24C16 serial 2-wire EEPROM,
    decode it and store it in the associated adapter struct for
    use by dvb_net.c

    This card appear to have the 24C16 write protect held to ground,
    thus permitting normal read/write operation. Theoretically it
    would be possible to write routines to burn a different (encoded)
    MAC address into the EEPROM.

    Robert Schlabbach   GMX
    Michael Glaum   KVH Industries
    Holger Waechtler    Convergence

    Copyright (C) 2002-2003 Ralph Metzler <[email protected]>
                Metzler Brothers Systementwicklung GbR

    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.

*/

#include <asm/errno.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/string.h>
#include <linux/i2c.h>

#include "ttpci-eeprom.h"

#if 1
#define dprintk(x...) do { printk(x); } while (0)
#else
#define dprintk(x...) do { } while (0)
#endif


static int check_mac_tt(u8 *buf)
{
    int i;
    u16 tmp = 0xffff;

    for (i = 0; i < 8; i++) {
        tmp  = (tmp << 8) | ((tmp >> 8) ^ buf[i]);
        tmp ^= (tmp >> 4) & 0x0f;
        tmp ^= (tmp << 12) ^ ((tmp & 0xff) << 5);
    }
    tmp ^= 0xffff;
    return (((tmp >> 8) ^ buf[8]) | ((tmp & 0xff) ^ buf[9]));
}

static int getmac_tt(u8 * decodedMAC, u8 * encodedMAC)
{
    u8 xor[20] = { 0x72, 0x23, 0x68, 0x19, 0x5c, 0xa8, 0x71, 0x2c,
               0x54, 0xd3, 0x7b, 0xf1, 0x9E, 0x23, 0x16, 0xf6,
               0x1d, 0x36, 0x64, 0x78};
    u8 data[20];
    int i;

    /* In case there is a sig check failure have the orig contents available */
    memcpy(data, encodedMAC, 20);

    for (i = 0; i < 20; i++)
        data[i] ^= xor[i];
    for (i = 0; i < 10; i++)
        data[i] = ((data[2 * i + 1] << 8) | data[2 * i])
            >> ((data[2 * i + 1] >> 6) & 3);

    if (check_mac_tt(data))
        return -ENODEV;

    decodedMAC[0] = data[2]; decodedMAC[1] = data[1]; decodedMAC[2] = data[0];
    decodedMAC[3] = data[6]; decodedMAC[4] = data[5]; decodedMAC[5] = data[4];
    return 0;
}

int ttpci_eeprom_decode_mac(u8 *decodedMAC, u8 *encodedMAC)
{
    u8 xor[20] = { 0x72, 0x23, 0x68, 0x19, 0x5c, 0xa8, 0x71, 0x2c,
               0x54, 0xd3, 0x7b, 0xf1, 0x9E, 0x23, 0x16, 0xf6,
               0x1d, 0x36, 0x64, 0x78};
    u8 data[20];
    int i;

    memcpy(data, encodedMAC, 20);

    for (i = 0; i < 20; i++)
        data[i] ^= xor[i];
    for (i = 0; i < 10; i++)
        data[i] = ((data[2 * i + 1] << 8) | data[2 * i])
            >> ((data[2 * i + 1] >> 6) & 3);

    if (check_mac_tt(data))
        return -ENODEV;

    decodedMAC[0] = data[2];
    decodedMAC[1] = data[1];
    decodedMAC[2] = data[0];
    decodedMAC[3] = data[6];
    decodedMAC[4] = data[5];
    decodedMAC[5] = data[4];
    return 0;
}
EXPORT_SYMBOL(ttpci_eeprom_decode_mac);

static int ttpci_eeprom_read_encodedMAC(struct i2c_adapter *adapter, u8 * encodedMAC)
{
    int ret;
    u8 b0[] = { 0xcc };

    struct i2c_msg msg[] = {
        { .addr = 0x50, .flags = 0, .buf = b0, .len = 1 },
        { .addr = 0x50, .flags = I2C_M_RD, .buf = encodedMAC, .len = 20 }
    };

    /* dprintk("%s\n", __func__); */

    ret = i2c_transfer(adapter, msg, 2);

    if (ret != 2)       /* Assume EEPROM isn't there */
        return (-ENODEV);

    return 0;
}


int ttpci_eeprom_parse_mac(struct i2c_adapter *adapter, u8 *proposed_mac)
{
    int ret, i;
    u8 encodedMAC[20];
    u8 decodedMAC[6];

    ret = ttpci_eeprom_read_encodedMAC(adapter, encodedMAC);

    if (ret != 0) {     /* Will only be -ENODEV */
        dprintk("Couldn't read from EEPROM: not there?\n");
        memset(proposed_mac, 0, 6);
        return ret;
    }

    ret = getmac_tt(decodedMAC, encodedMAC);
    if( ret != 0 ) {
        dprintk("adapter failed MAC signature check\n");
        dprintk("encoded MAC from EEPROM was " );
        for(i=0; i<19; i++) {
            dprintk( "%.2x:", encodedMAC[i]);
        }
        dprintk("%.2x\n", encodedMAC[19]);
        memset(proposed_mac, 0, 6);
        return ret;
    }

    memcpy(proposed_mac, decodedMAC, 6);
    dprintk("adapter has MAC addr = %.2x:%.2x:%.2x:%.2x:%.2x:%.2x\n",
        decodedMAC[0], decodedMAC[1], decodedMAC[2],
        decodedMAC[3], decodedMAC[4], decodedMAC[5]);
    return 0;
}

EXPORT_SYMBOL(ttpci_eeprom_parse_mac);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Ralph Metzler, Marcus Metzler, others");
MODULE_DESCRIPTION("Decode dvb_net MAC address from EEPROM of PCI DVB cards "
        "made by Siemens, Technotrend, Hauppauge");