linux/Documentation/misc-devices/eeprom
<<
>>
Prefs
   1Kernel driver eeprom
   2====================
   3
   4Supported 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
  38Authors:
  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
  45Description
  46-----------
  47
  48This is a simple EEPROM module meant to enable reading the first 256 bytes
  49of an EEPROM (on a SDRAM DIMM for example). However, it will access serial
  50EEPROMs on any I2C adapter. The supported devices are generically called
  5124Cxx, and are listed above; however the numbering for these
  52industry-standard devices may vary by manufacturer.
  53
  54This module was a programming exercise to get used to the new project
  55organization laid out by Frodo, but it should be at least completely
  56effective for decoding the contents of EEPROMs on DIMMs.
  57
  58DIMMS will typically contain a 24C01A or 24C02, or the 34C02 variants.
  59The other devices will not be found on a DIMM because they respond to more
  60than one address.
  61
  62DDC Monitors may contain any device. Often a 24C01, which responds to all 8
  63addresses, is found.
  64
  65Recent Sony Vaio laptops have an EEPROM at 0x57. We couldn't get the
  66specification, so it is guess work and far from being complete.
  67
  68The Microchip 24AA52/24LCS52, ST M34C02, and others support an additional
  69software write protect register at 0x30 - 0x37 (0x20 less than the memory
  70location). The chip responds to "write quick" detection at this address but
  71does not respond to byte reads. If this register is present, the lower 128
  72bytes of the memory array are not write protected. Any byte data write to
  73this address will write protect the memory array permanently, and the
  74device will no longer respond at the 0x30-37 address. The eeprom driver
  75does not support this register.
  76
  77Lacking functionality:
  78
  79* Full support for larger devices (24C04, 24C08, 24C16). These are not
  80typically found on a PC. These devices will appear as separate devices at
  81multiple addresses.
  82
  83* Support for really large devices (24C32, 24C64, 24C128, 24C256, 24C512).
  84These devices require two-byte address fields and are not supported.
  85
  86* Enable Writing. Again, no technical reason why not, but making it easy
  87to change the contents of the EEPROMs (on DIMMs anyway) also makes it easy
  88to disable the DIMMs (potentially preventing the computer from booting)
  89until the values are restored somehow.
  90
  91Use:
  92
  93After inserting the module (and any other required SMBus/i2c modules), you
  94should have some EEPROM directories in /sys/bus/i2c/devices/* of names such
  95as "0-0050". Inside each of these is a series of files, the eeprom file
  96contains the binary data from EEPROM.
  97
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.