From 9b5db89ea4bfdbb23d4f85f3a7fbf2cd36d20146 Mon Sep 17 00:00:00 2001 From: Mauro Carvalho Chehab Date: Fri, 28 Jun 2019 18:23:13 -0300 Subject: docs: misc-devices: convert files without extension to ReST Those files are also text files. Convert them to ReST and add to the misc-files index.rst. Signed-off-by: Mauro Carvalho Chehab Link: https://lore.kernel.org/r/b7dc829809673bd8cffe0e7bbe9c9308681c6fe2.1561756511.git.mchehab+samsung@kernel.org Signed-off-by: Greg Kroah-Hartman --- Documentation/misc-devices/eeprom.rst | 107 ++++++++++++++++++++++++++++++++++ 1 file changed, 107 insertions(+) create mode 100644 Documentation/misc-devices/eeprom.rst (limited to 'Documentation/misc-devices/eeprom.rst') diff --git a/Documentation/misc-devices/eeprom.rst b/Documentation/misc-devices/eeprom.rst new file mode 100644 index 000000000000..008249675ccc --- /dev/null +++ b/Documentation/misc-devices/eeprom.rst @@ -0,0 +1,107 @@ +==================== +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 , + - Philip Edelbrock , + - Jean Delvare , + - Greg Kroah-Hartman , + - 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. -- cgit v1.2.3