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- Kernel driver eeprom
- ====================
- Supported chips:
- * Any EEPROM chip in the designated address range
- Prefix: 'eeprom'
- Addresses scanned: I2C 0x50 - 0x57
- Datasheets: Publicly available from:
- Atmel (www.atmel.com),
- Catalyst (www.catsemi.com),
- Fairchild (www.fairchildsemi.com),
- Microchip (www.microchip.com),
- Philips (www.semiconductor.philips.com),
- Rohm (www.rohm.com),
- ST (www.st.com),
- Xicor (www.xicor.com),
- and others.
- Chip Size (bits) Address
- 24C01 1K 0x50 (shadows at 0x51 - 0x57)
- 24C01A 1K 0x50 - 0x57 (Typical device on DIMMs)
- 24C02 2K 0x50 - 0x57
- 24C04 4K 0x50, 0x52, 0x54, 0x56
- (additional data at 0x51, 0x53, 0x55, 0x57)
- 24C08 8K 0x50, 0x54 (additional data at 0x51, 0x52,
- 0x53, 0x55, 0x56, 0x57)
- 24C16 16K 0x50 (additional data at 0x51 - 0x57)
- Sony 2K 0x57
- Atmel 34C02B 2K 0x50 - 0x57, SW write protect at 0x30-37
- Catalyst 34FC02 2K 0x50 - 0x57, SW write protect at 0x30-37
- Catalyst 34RC02 2K 0x50 - 0x57, SW write protect at 0x30-37
- Fairchild 34W02 2K 0x50 - 0x57, SW write protect at 0x30-37
- Microchip 24AA52 2K 0x50 - 0x57, SW write protect at 0x30-37
- ST M34C02 2K 0x50 - 0x57, SW write protect at 0x30-37
- Authors:
- Frodo Looijaard <frodol@dds.nl>,
- Philip Edelbrock <phil@netroedge.com>,
- Jean Delvare <jdelvare@suse.de>,
- Greg Kroah-Hartman <greg@kroah.com>,
- IBM Corp.
- Description
- -----------
- This is a simple EEPROM module meant to enable reading the first 256 bytes
- of an EEPROM (on a SDRAM DIMM for example). However, it will access serial
- EEPROMs on any I2C adapter. The supported devices are generically called
- 24Cxx, and are listed above; however the numbering for these
- industry-standard devices may vary by manufacturer.
- This module was a programming exercise to get used to the new project
- organization laid out by Frodo, but it should be at least completely
- effective for decoding the contents of EEPROMs on DIMMs.
- DIMMS will typically contain a 24C01A or 24C02, or the 34C02 variants.
- The other devices will not be found on a DIMM because they respond to more
- than one address.
- DDC Monitors may contain any device. Often a 24C01, which responds to all 8
- addresses, is found.
- Recent Sony Vaio laptops have an EEPROM at 0x57. We couldn't get the
- specification, so it is guess work and far from being complete.
- The Microchip 24AA52/24LCS52, ST M34C02, and others support an additional
- software write protect register at 0x30 - 0x37 (0x20 less than the memory
- location). The chip responds to "write quick" detection at this address but
- does not respond to byte reads. If this register is present, the lower 128
- bytes of the memory array are not write protected. Any byte data write to
- this address will write protect the memory array permanently, and the
- device will no longer respond at the 0x30-37 address. The eeprom driver
- does not support this register.
- Lacking functionality:
- * Full support for larger devices (24C04, 24C08, 24C16). These are not
- typically found on a PC. These devices will appear as separate devices at
- multiple addresses.
- * Support for really large devices (24C32, 24C64, 24C128, 24C256, 24C512).
- These devices require two-byte address fields and are not supported.
- * Enable Writing. Again, no technical reason why not, but making it easy
- to change the contents of the EEPROMs (on DIMMs anyway) also makes it easy
- to disable the DIMMs (potentially preventing the computer from booting)
- until the values are restored somehow.
- Use:
- After inserting the module (and any other required SMBus/i2c modules), you
- should have some EEPROM directories in /sys/bus/i2c/devices/* of names such
- as "0-0050". Inside each of these is a series of files, the eeprom file
- contains the binary data from EEPROM.
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