0001 ====================
0002 Kernel driver eeprom
0003 ====================
0004
0005 Supported chips:
0006
0007 * Any EEPROM chip in the designated address range
0008
0009 Prefix: 'eeprom'
0010
0011 Addresses scanned: I2C 0x50 - 0x57
0012
0013 Datasheets: Publicly available from:
0014
0015 Atmel (www.atmel.com),
0016 Catalyst (www.catsemi.com),
0017 Fairchild (www.fairchildsemi.com),
0018 Microchip (www.microchip.com),
0019 Philips (www.semiconductor.philips.com),
0020 Rohm (www.rohm.com),
0021 ST (www.st.com),
0022 Xicor (www.xicor.com),
0023 and others.
0024
0025 ========= ============= ============================================
0026 Chip Size (bits) Address
0027 ========= ============= ============================================
0028 24C01 1K 0x50 (shadows at 0x51 - 0x57)
0029 24C01A 1K 0x50 - 0x57 (Typical device on DIMMs)
0030 24C02 2K 0x50 - 0x57
0031 24C04 4K 0x50, 0x52, 0x54, 0x56
0032 (additional data at 0x51, 0x53, 0x55, 0x57)
0033 24C08 8K 0x50, 0x54 (additional data at 0x51, 0x52,
0034 0x53, 0x55, 0x56, 0x57)
0035 24C16 16K 0x50 (additional data at 0x51 - 0x57)
0036 Sony 2K 0x57
0037
0038 Atmel 34C02B 2K 0x50 - 0x57, SW write protect at 0x30-37
0039 Catalyst 34FC02 2K 0x50 - 0x57, SW write protect at 0x30-37
0040 Catalyst 34RC02 2K 0x50 - 0x57, SW write protect at 0x30-37
0041 Fairchild 34W02 2K 0x50 - 0x57, SW write protect at 0x30-37
0042 Microchip 24AA52 2K 0x50 - 0x57, SW write protect at 0x30-37
0043 ST M34C02 2K 0x50 - 0x57, SW write protect at 0x30-37
0044 ========= ============= ============================================
0045
0046
0047 Authors:
0048 - Frodo Looijaard <frodol@dds.nl>,
0049 - Philip Edelbrock <phil@netroedge.com>,
0050 - Jean Delvare <jdelvare@suse.de>,
0051 - Greg Kroah-Hartman <greg@kroah.com>,
0052 - IBM Corp.
0053
0054 Description
0055 -----------
0056
0057 This is a simple EEPROM module meant to enable reading the first 256 bytes
0058 of an EEPROM (on a SDRAM DIMM for example). However, it will access serial
0059 EEPROMs on any I2C adapter. The supported devices are generically called
0060 24Cxx, and are listed above; however the numbering for these
0061 industry-standard devices may vary by manufacturer.
0062
0063 This module was a programming exercise to get used to the new project
0064 organization laid out by Frodo, but it should be at least completely
0065 effective for decoding the contents of EEPROMs on DIMMs.
0066
0067 DIMMS will typically contain a 24C01A or 24C02, or the 34C02 variants.
0068 The other devices will not be found on a DIMM because they respond to more
0069 than one address.
0070
0071 DDC Monitors may contain any device. Often a 24C01, which responds to all 8
0072 addresses, is found.
0073
0074 Recent Sony Vaio laptops have an EEPROM at 0x57. We couldn't get the
0075 specification, so it is guess work and far from being complete.
0076
0077 The Microchip 24AA52/24LCS52, ST M34C02, and others support an additional
0078 software write protect register at 0x30 - 0x37 (0x20 less than the memory
0079 location). The chip responds to "write quick" detection at this address but
0080 does not respond to byte reads. If this register is present, the lower 128
0081 bytes of the memory array are not write protected. Any byte data write to
0082 this address will write protect the memory array permanently, and the
0083 device will no longer respond at the 0x30-37 address. The eeprom driver
0084 does not support this register.
0085
0086 Lacking functionality
0087 ---------------------
0088
0089 * Full support for larger devices (24C04, 24C08, 24C16). These are not
0090 typically found on a PC. These devices will appear as separate devices at
0091 multiple addresses.
0092
0093 * Support for really large devices (24C32, 24C64, 24C128, 24C256, 24C512).
0094 These devices require two-byte address fields and are not supported.
0095
0096 * Enable Writing. Again, no technical reason why not, but making it easy
0097 to change the contents of the EEPROMs (on DIMMs anyway) also makes it easy
0098 to disable the DIMMs (potentially preventing the computer from booting)
0099 until the values are restored somehow.
0100
0101 Use
0102 ---
0103
0104 After inserting the module (and any other required SMBus/i2c modules), you
0105 should have some EEPROM directories in ``/sys/bus/i2c/devices/*`` of names such
0106 as "0-0050". Inside each of these is a series of files, the eeprom file
0107 contains the binary data from EEPROM.
