Commit | Line | Data |
---|---|---|
9b5db89e | 1 | ==================== |
7f15b664 M |
2 | Kernel driver eeprom |
3 | ==================== | |
4 | ||
5 | Supported chips: | |
9b5db89e | 6 | |
7f15b664 | 7 | * Any EEPROM chip in the designated address range |
9b5db89e | 8 | |
7f15b664 | 9 | Prefix: 'eeprom' |
9b5db89e | 10 | |
7f15b664 | 11 | Addresses scanned: I2C 0x50 - 0x57 |
9b5db89e | 12 | |
7f15b664 | 13 | Datasheets: Publicly available from: |
9b5db89e | 14 | |
7f15b664 M |
15 | Atmel (www.atmel.com), |
16 | Catalyst (www.catsemi.com), | |
17 | Fairchild (www.fairchildsemi.com), | |
18 | Microchip (www.microchip.com), | |
19 | Philips (www.semiconductor.philips.com), | |
20 | Rohm (www.rohm.com), | |
21 | ST (www.st.com), | |
22 | Xicor (www.xicor.com), | |
23 | and others. | |
24 | ||
9b5db89e MCC |
25 | ========= ============= ============================================ |
26 | Chip Size (bits) Address | |
27 | ========= ============= ============================================ | |
7f15b664 M |
28 | 24C01 1K 0x50 (shadows at 0x51 - 0x57) |
29 | 24C01A 1K 0x50 - 0x57 (Typical device on DIMMs) | |
30 | 24C02 2K 0x50 - 0x57 | |
31 | 24C04 4K 0x50, 0x52, 0x54, 0x56 | |
32 | (additional data at 0x51, 0x53, 0x55, 0x57) | |
33 | 24C08 8K 0x50, 0x54 (additional data at 0x51, 0x52, | |
34 | 0x53, 0x55, 0x56, 0x57) | |
9b5db89e | 35 | 24C16 16K 0x50 (additional data at 0x51 - 0x57) |
7f15b664 M |
36 | Sony 2K 0x57 |
37 | ||
38 | Atmel 34C02B 2K 0x50 - 0x57, SW write protect at 0x30-37 | |
39 | Catalyst 34FC02 2K 0x50 - 0x57, SW write protect at 0x30-37 | |
40 | Catalyst 34RC02 2K 0x50 - 0x57, SW write protect at 0x30-37 | |
41 | Fairchild 34W02 2K 0x50 - 0x57, SW write protect at 0x30-37 | |
42 | Microchip 24AA52 2K 0x50 - 0x57, SW write protect at 0x30-37 | |
43 | ST M34C02 2K 0x50 - 0x57, SW write protect at 0x30-37 | |
9b5db89e | 44 | ========= ============= ============================================ |
7f15b664 M |
45 | |
46 | ||
47 | Authors: | |
9b5db89e MCC |
48 | - Frodo Looijaard <frodol@dds.nl>, |
49 | - Philip Edelbrock <phil@netroedge.com>, | |
50 | - Jean Delvare <jdelvare@suse.de>, | |
51 | - Greg Kroah-Hartman <greg@kroah.com>, | |
52 | - IBM Corp. | |
7f15b664 M |
53 | |
54 | Description | |
55 | ----------- | |
56 | ||
57 | This is a simple EEPROM module meant to enable reading the first 256 bytes | |
58 | of an EEPROM (on a SDRAM DIMM for example). However, it will access serial | |
59 | EEPROMs on any I2C adapter. The supported devices are generically called | |
60 | 24Cxx, and are listed above; however the numbering for these | |
61 | industry-standard devices may vary by manufacturer. | |
62 | ||
63 | This module was a programming exercise to get used to the new project | |
64 | organization laid out by Frodo, but it should be at least completely | |
65 | effective for decoding the contents of EEPROMs on DIMMs. | |
66 | ||
67 | DIMMS will typically contain a 24C01A or 24C02, or the 34C02 variants. | |
68 | The other devices will not be found on a DIMM because they respond to more | |
69 | than one address. | |
70 | ||
71 | DDC Monitors may contain any device. Often a 24C01, which responds to all 8 | |
72 | addresses, is found. | |
73 | ||
74 | Recent Sony Vaio laptops have an EEPROM at 0x57. We couldn't get the | |
75 | specification, so it is guess work and far from being complete. | |
76 | ||
77 | The Microchip 24AA52/24LCS52, ST M34C02, and others support an additional | |
78 | software write protect register at 0x30 - 0x37 (0x20 less than the memory | |
79 | location). The chip responds to "write quick" detection at this address but | |
80 | does not respond to byte reads. If this register is present, the lower 128 | |
81 | bytes of the memory array are not write protected. Any byte data write to | |
82 | this address will write protect the memory array permanently, and the | |
83 | device will no longer respond at the 0x30-37 address. The eeprom driver | |
84 | does not support this register. | |
85 | ||
9b5db89e MCC |
86 | Lacking functionality |
87 | --------------------- | |
7f15b664 M |
88 | |
89 | * Full support for larger devices (24C04, 24C08, 24C16). These are not | |
9b5db89e MCC |
90 | typically found on a PC. These devices will appear as separate devices at |
91 | multiple addresses. | |
7f15b664 M |
92 | |
93 | * Support for really large devices (24C32, 24C64, 24C128, 24C256, 24C512). | |
9b5db89e | 94 | These devices require two-byte address fields and are not supported. |
7f15b664 M |
95 | |
96 | * Enable Writing. Again, no technical reason why not, but making it easy | |
9b5db89e MCC |
97 | to change the contents of the EEPROMs (on DIMMs anyway) also makes it easy |
98 | to disable the DIMMs (potentially preventing the computer from booting) | |
99 | until the values are restored somehow. | |
7f15b664 | 100 | |
9b5db89e MCC |
101 | Use |
102 | --- | |
7f15b664 M |
103 | |
104 | After inserting the module (and any other required SMBus/i2c modules), you | |
9b5db89e | 105 | should have some EEPROM directories in ``/sys/bus/i2c/devices/*`` of names such |
7f15b664 M |
106 | as "0-0050". Inside each of these is a series of files, the eeprom file |
107 | contains the binary data from EEPROM. |