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 
check_mac_tt(u8 * buf)38 static 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 
getmac_tt(u8 * decodedMAC,u8 * encodedMAC)52 static 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 
ttpci_eeprom_decode_mac(u8 * decodedMAC,u8 * encodedMAC)77 int 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 }
104 EXPORT_SYMBOL(ttpci_eeprom_decode_mac);
105 
ttpci_eeprom_read_encodedMAC(struct i2c_adapter * adapter,u8 * encodedMAC)106 static 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 
ttpci_eeprom_parse_mac(struct i2c_adapter * adapter,u8 * proposed_mac)127 int 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 
155 EXPORT_SYMBOL(ttpci_eeprom_parse_mac);
156 
157 MODULE_LICENSE("GPL");
158 MODULE_AUTHOR("Ralph Metzler, Marcus Metzler, others");
159 MODULE_DESCRIPTION("Decode dvb_net MAC address from EEPROM of PCI DVB cards made by Siemens, Technotrend, Hauppauge");
160