ttpci-eeprom.c

  1// SPDX-License-Identifier: GPL-2.0-or-later
  2/*
  3    Retrieve encoded MAC address from 24C16 serial 2-wire EEPROM,
  4    decode it and store it in the associated adapter struct for
  5    use by dvb_net.c
  6
  7    This card appear to have the 24C16 write protect held to ground,
  8    thus permitting normal read/write operation. Theoretically it
  9    would be possible to write routines to burn a different (encoded)
 10    MAC address into the EEPROM.
 11
 12    Robert Schlabbach	GMX
 13    Michael Glaum	KVH Industries
 14    Holger Waechtler	Convergence
 15
 16    Copyright (C) 2002-2003 Ralph Metzler <rjkm@metzlerbros.de>
 17			    Metzler Brothers Systementwicklung GbR
 18
 19
 20*/
 21
 22#include <asm/errno.h>
 23#include <linux/init.h>
 24#include <linux/module.h>
 25#include <linux/string.h>
 26#include <linux/i2c.h>
 27#include <linux/etherdevice.h>
 28
 29#include "ttpci-eeprom.h"
 30
 31#if 1
 32#define dprintk(x...) do { printk(x); } while (0)
 33#else
 34#define dprintk(x...) do { } while (0)
 35#endif
 36
 37
 38static int check_mac_tt(u8 *buf)
 39{
 40	int i;
 41	u16 tmp = 0xffff;
 42
 43	for (i = 0; i < 8; i++) {
 44		tmp  = (tmp << 8) | ((tmp >> 8) ^ buf[i]);
 45		tmp ^= (tmp >> 4) & 0x0f;
 46		tmp ^= (tmp << 12) ^ ((tmp & 0xff) << 5);
 47	}
 48	tmp ^= 0xffff;
 49	return (((tmp >> 8) ^ buf[8]) | ((tmp & 0xff) ^ buf[9]));
 50}
 51
 52static int getmac_tt(u8 * decodedMAC, u8 * encodedMAC)
 53{
 54	u8 xor[20] = { 0x72, 0x23, 0x68, 0x19, 0x5c, 0xa8, 0x71, 0x2c,
 55		       0x54, 0xd3, 0x7b, 0xf1, 0x9E, 0x23, 0x16, 0xf6,
 56		       0x1d, 0x36, 0x64, 0x78};
 57	u8 data[20];
 58	int i;
 59
 60	/* In case there is a sig check failure have the orig contents available */
 61	memcpy(data, encodedMAC, 20);
 62
 63	for (i = 0; i < 20; i++)
 64		data[i] ^= xor[i];
 65	for (i = 0; i < 10; i++)
 66		data[i] = ((data[2 * i + 1] << 8) | data[2 * i])
 67			>> ((data[2 * i + 1] >> 6) & 3);
 68
 69	if (check_mac_tt(data))
 70		return -ENODEV;
 71
 72	decodedMAC[0] = data[2]; decodedMAC[1] = data[1]; decodedMAC[2] = data[0];
 73	decodedMAC[3] = data[6]; decodedMAC[4] = data[5]; decodedMAC[5] = data[4];
 74	return 0;
 75}
 76
 77int ttpci_eeprom_decode_mac(u8 *decodedMAC, u8 *encodedMAC)
 78{
 79	u8 xor[20] = { 0x72, 0x23, 0x68, 0x19, 0x5c, 0xa8, 0x71, 0x2c,
 80		       0x54, 0xd3, 0x7b, 0xf1, 0x9E, 0x23, 0x16, 0xf6,
 81		       0x1d, 0x36, 0x64, 0x78};
 82	u8 data[20];
 83	int i;
 84
 85	memcpy(data, encodedMAC, 20);
 86
 87	for (i = 0; i < 20; i++)
 88		data[i] ^= xor[i];
 89	for (i = 0; i < 10; i++)
 90		data[i] = ((data[2 * i + 1] << 8) | data[2 * i])
 91			>> ((data[2 * i + 1] >> 6) & 3);
 92
 93	if (check_mac_tt(data))
 94		return -ENODEV;
 95
 96	decodedMAC[0] = data[2];
 97	decodedMAC[1] = data[1];
 98	decodedMAC[2] = data[0];
 99	decodedMAC[3] = data[6];
100	decodedMAC[4] = data[5];
101	decodedMAC[5] = data[4];
102	return 0;
103}
104EXPORT_SYMBOL(ttpci_eeprom_decode_mac);
105
106static int ttpci_eeprom_read_encodedMAC(struct i2c_adapter *adapter, u8 * encodedMAC)
107{
108	int ret;
109	u8 b0[] = { 0xcc };
110
111	struct i2c_msg msg[] = {
112		{ .addr = 0x50, .flags = 0, .buf = b0, .len = 1 },
113		{ .addr = 0x50, .flags = I2C_M_RD, .buf = encodedMAC, .len = 20 }
114	};
115
116	/* dprintk("%s\n", __func__); */
117
118	ret = i2c_transfer(adapter, msg, 2);
119
120	if (ret != 2)		/* Assume EEPROM isn't there */
121		return (-ENODEV);
122
123	return 0;
124}
125
126
127int ttpci_eeprom_parse_mac(struct i2c_adapter *adapter, u8 *proposed_mac)
128{
129	int ret;
130	u8 encodedMAC[20];
131	u8 decodedMAC[6];
132
133	ret = ttpci_eeprom_read_encodedMAC(adapter, encodedMAC);
134
135	if (ret != 0) {		/* Will only be -ENODEV */
136		dprintk("Couldn't read from EEPROM: not there?\n");
137		eth_zero_addr(proposed_mac);
138		return ret;
139	}
140
141	ret = getmac_tt(decodedMAC, encodedMAC);
142	if( ret != 0 ) {
143		dprintk("adapter failed MAC signature check\n");
144		dprintk("encoded MAC from EEPROM was %*phC",
145			(int)sizeof(encodedMAC), &encodedMAC);
146		eth_zero_addr(proposed_mac);
147		return ret;
148	}
149
150	memcpy(proposed_mac, decodedMAC, 6);
151	dprintk("adapter has MAC addr = %pM\n", decodedMAC);
152	return 0;
153}
154
155EXPORT_SYMBOL(ttpci_eeprom_parse_mac);
156
157MODULE_LICENSE("GPL");
158MODULE_AUTHOR("Ralph Metzler, Marcus Metzler, others");
159MODULE_DESCRIPTION("Decode dvb_net MAC address from EEPROM of PCI DVB cards made by Siemens, Technotrend, Hauppauge");