xref: /linux/drivers/media/common/ttpci-eeprom.c (revision de646852cdadf7da2267e06297f7f6fe22dfb899)
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  
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  
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  
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  
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  
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