Commit | Line | Data |
---|---|---|
7f15b664 M |
1 | Kernel driver eeprom |
2 | ==================== | |
3 | ||
4 | Supported chips: | |
5 | * Any EEPROM chip in the designated address range | |
6 | Prefix: 'eeprom' | |
7 | Addresses scanned: I2C 0x50 - 0x57 | |
8 | Datasheets: Publicly available from: | |
9 | Atmel (www.atmel.com), | |
10 | Catalyst (www.catsemi.com), | |
11 | Fairchild (www.fairchildsemi.com), | |
12 | Microchip (www.microchip.com), | |
13 | Philips (www.semiconductor.philips.com), | |
14 | Rohm (www.rohm.com), | |
15 | ST (www.st.com), | |
16 | Xicor (www.xicor.com), | |
17 | and others. | |
18 | ||
19 | Chip Size (bits) Address | |
20 | 24C01 1K 0x50 (shadows at 0x51 - 0x57) | |
21 | 24C01A 1K 0x50 - 0x57 (Typical device on DIMMs) | |
22 | 24C02 2K 0x50 - 0x57 | |
23 | 24C04 4K 0x50, 0x52, 0x54, 0x56 | |
24 | (additional data at 0x51, 0x53, 0x55, 0x57) | |
25 | 24C08 8K 0x50, 0x54 (additional data at 0x51, 0x52, | |
26 | 0x53, 0x55, 0x56, 0x57) | |
27 | 24C16 16K 0x50 (additional data at 0x51 - 0x57) | |
28 | Sony 2K 0x57 | |
29 | ||
30 | Atmel 34C02B 2K 0x50 - 0x57, SW write protect at 0x30-37 | |
31 | Catalyst 34FC02 2K 0x50 - 0x57, SW write protect at 0x30-37 | |
32 | Catalyst 34RC02 2K 0x50 - 0x57, SW write protect at 0x30-37 | |
33 | Fairchild 34W02 2K 0x50 - 0x57, SW write protect at 0x30-37 | |
34 | Microchip 24AA52 2K 0x50 - 0x57, SW write protect at 0x30-37 | |
35 | ST M34C02 2K 0x50 - 0x57, SW write protect at 0x30-37 | |
36 | ||
37 | ||
38 | Authors: | |
39 | Frodo Looijaard <frodol@dds.nl>, | |
40 | Philip Edelbrock <phil@netroedge.com>, | |
41 | Jean Delvare <khali@linux-fr.org>, | |
42 | Greg Kroah-Hartman <greg@kroah.com>, | |
43 | IBM Corp. | |
44 | ||
45 | Description | |
46 | ----------- | |
47 | ||
48 | This is a simple EEPROM module meant to enable reading the first 256 bytes | |
49 | of an EEPROM (on a SDRAM DIMM for example). However, it will access serial | |
50 | EEPROMs on any I2C adapter. The supported devices are generically called | |
51 | 24Cxx, and are listed above; however the numbering for these | |
52 | industry-standard devices may vary by manufacturer. | |
53 | ||
54 | This module was a programming exercise to get used to the new project | |
55 | organization laid out by Frodo, but it should be at least completely | |
56 | effective for decoding the contents of EEPROMs on DIMMs. | |
57 | ||
58 | DIMMS will typically contain a 24C01A or 24C02, or the 34C02 variants. | |
59 | The other devices will not be found on a DIMM because they respond to more | |
60 | than one address. | |
61 | ||
62 | DDC Monitors may contain any device. Often a 24C01, which responds to all 8 | |
63 | addresses, is found. | |
64 | ||
65 | Recent Sony Vaio laptops have an EEPROM at 0x57. We couldn't get the | |
66 | specification, so it is guess work and far from being complete. | |
67 | ||
68 | The Microchip 24AA52/24LCS52, ST M34C02, and others support an additional | |
69 | software write protect register at 0x30 - 0x37 (0x20 less than the memory | |
70 | location). The chip responds to "write quick" detection at this address but | |
71 | does not respond to byte reads. If this register is present, the lower 128 | |
72 | bytes of the memory array are not write protected. Any byte data write to | |
73 | this address will write protect the memory array permanently, and the | |
74 | device will no longer respond at the 0x30-37 address. The eeprom driver | |
75 | does not support this register. | |
76 | ||
77 | Lacking functionality: | |
78 | ||
79 | * Full support for larger devices (24C04, 24C08, 24C16). These are not | |
80 | typically found on a PC. These devices will appear as separate devices at | |
81 | multiple addresses. | |
82 | ||
83 | * Support for really large devices (24C32, 24C64, 24C128, 24C256, 24C512). | |
84 | These devices require two-byte address fields and are not supported. | |
85 | ||
86 | * Enable Writing. Again, no technical reason why not, but making it easy | |
87 | to change the contents of the EEPROMs (on DIMMs anyway) also makes it easy | |
88 | to disable the DIMMs (potentially preventing the computer from booting) | |
89 | until the values are restored somehow. | |
90 | ||
91 | Use: | |
92 | ||
93 | After inserting the module (and any other required SMBus/i2c modules), you | |
94 | should have some EEPROM directories in /sys/bus/i2c/devices/* of names such | |
95 | as "0-0050". Inside each of these is a series of files, the eeprom file | |
96 | contains the binary data from EEPROM. |