| Kyle Swenson | 8d8f654 | 2021-03-15 11:02:55 -0600 | [diff] [blame] | 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 <jdelvare@suse.de>, |
| 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. |