eeprom.rst (4490B)
1==================== 2Kernel driver eeprom 3==================== 4 5Supported chips: 6 7 * Any EEPROM chip in the designated address range 8 9 Prefix: 'eeprom' 10 11 Addresses scanned: I2C 0x50 - 0x57 12 13 Datasheets: Publicly available from: 14 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 25 ========= ============= ============================================ 26 Chip Size (bits) Address 27 ========= ============= ============================================ 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) 35 24C16 16K 0x50 (additional data at 0x51 - 0x57) 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 44 ========= ============= ============================================ 45 46 47Authors: 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. 53 54Description 55----------- 56 57This is a simple EEPROM module meant to enable reading the first 256 bytes 58of an EEPROM (on a SDRAM DIMM for example). However, it will access serial 59EEPROMs on any I2C adapter. The supported devices are generically called 6024Cxx, and are listed above; however the numbering for these 61industry-standard devices may vary by manufacturer. 62 63This module was a programming exercise to get used to the new project 64organization laid out by Frodo, but it should be at least completely 65effective for decoding the contents of EEPROMs on DIMMs. 66 67DIMMS will typically contain a 24C01A or 24C02, or the 34C02 variants. 68The other devices will not be found on a DIMM because they respond to more 69than one address. 70 71DDC Monitors may contain any device. Often a 24C01, which responds to all 8 72addresses, is found. 73 74Recent Sony Vaio laptops have an EEPROM at 0x57. We couldn't get the 75specification, so it is guess work and far from being complete. 76 77The Microchip 24AA52/24LCS52, ST M34C02, and others support an additional 78software write protect register at 0x30 - 0x37 (0x20 less than the memory 79location). The chip responds to "write quick" detection at this address but 80does not respond to byte reads. If this register is present, the lower 128 81bytes of the memory array are not write protected. Any byte data write to 82this address will write protect the memory array permanently, and the 83device will no longer respond at the 0x30-37 address. The eeprom driver 84does not support this register. 85 86Lacking functionality 87--------------------- 88 89* Full support for larger devices (24C04, 24C08, 24C16). These are not 90 typically found on a PC. These devices will appear as separate devices at 91 multiple addresses. 92 93* Support for really large devices (24C32, 24C64, 24C128, 24C256, 24C512). 94 These devices require two-byte address fields and are not supported. 95 96* Enable Writing. Again, no technical reason why not, but making it easy 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. 100 101Use 102--- 103 104After inserting the module (and any other required SMBus/i2c modules), you 105should have some EEPROM directories in ``/sys/bus/i2c/devices/*`` of names such 106as "0-0050". Inside each of these is a series of files, the eeprom file 107contains the binary data from EEPROM.