| ==================== |
| 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. |
