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Diffstat (limited to 'Documentation/misc-devices')
| -rw-r--r-- | Documentation/misc-devices/eeprom | 96 | ||||
| -rw-r--r-- | Documentation/misc-devices/max6875 | 108 |
2 files changed, 204 insertions, 0 deletions
diff --git a/Documentation/misc-devices/eeprom b/Documentation/misc-devices/eeprom new file mode 100644 index 000000000000..f7e8104b5764 --- /dev/null +++ b/Documentation/misc-devices/eeprom @@ -0,0 +1,96 @@ +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 <khali@linux-fr.org>, + 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. diff --git a/Documentation/misc-devices/max6875 b/Documentation/misc-devices/max6875 new file mode 100644 index 000000000000..10ca43cd1a72 --- /dev/null +++ b/Documentation/misc-devices/max6875 @@ -0,0 +1,108 @@ +Kernel driver max6875 +===================== + +Supported chips: + * Maxim MAX6874, MAX6875 + Prefix: 'max6875' + Addresses scanned: None (see below) + Datasheet: + http://pdfserv.maxim-ic.com/en/ds/MAX6874-MAX6875.pdf + +Author: Ben Gardner <bgardner@wabtec.com> + + +Description +----------- + +The Maxim MAX6875 is an EEPROM-programmable power-supply sequencer/supervisor. +It provides timed outputs that can be used as a watchdog, if properly wired. +It also provides 512 bytes of user EEPROM. + +At reset, the MAX6875 reads the configuration EEPROM into its configuration +registers. The chip then begins to operate according to the values in the +registers. + +The Maxim MAX6874 is a similar, mostly compatible device, with more intputs +and outputs: + vin gpi vout +MAX6874 6 4 8 +MAX6875 4 3 5 + +See the datasheet for more information. + + +Sysfs entries +------------- + +eeprom - 512 bytes of user-defined EEPROM space. + + +General Remarks +--------------- + +Valid addresses for the MAX6875 are 0x50 and 0x52. +Valid addresses for the MAX6874 are 0x50, 0x52, 0x54 and 0x56. +The driver does not probe any address, so you must force the address. + +Example: +$ modprobe max6875 force=0,0x50 + +The MAX6874/MAX6875 ignores address bit 0, so this driver attaches to multiple +addresses. For example, for address 0x50, it also reserves 0x51. +The even-address instance is called 'max6875', the odd one is 'dummy'. + + +Programming the chip using i2c-dev +---------------------------------- + +Use the i2c-dev interface to access and program the chips. +Reads and writes are performed differently depending on the address range. + +The configuration registers are at addresses 0x00 - 0x45. +Use i2c_smbus_write_byte_data() to write a register and +i2c_smbus_read_byte_data() to read a register. +The command is the register number. + +Examples: +To write a 1 to register 0x45: + i2c_smbus_write_byte_data(fd, 0x45, 1); + +To read register 0x45: + value = i2c_smbus_read_byte_data(fd, 0x45); + + +The configuration EEPROM is at addresses 0x8000 - 0x8045. +The user EEPROM is at addresses 0x8100 - 0x82ff. + +Use i2c_smbus_write_word_data() to write a byte to EEPROM. + +The command is the upper byte of the address: 0x80, 0x81, or 0x82. +The data word is the lower part of the address or'd with data << 8. + cmd = address >> 8; + val = (address & 0xff) | (data << 8); + +Example: +To write 0x5a to address 0x8003: + i2c_smbus_write_word_data(fd, 0x80, 0x5a03); + + +Reading data from the EEPROM is a little more complicated. +Use i2c_smbus_write_byte_data() to set the read address and then +i2c_smbus_read_byte() or i2c_smbus_read_i2c_block_data() to read the data. + +Example: +To read data starting at offset 0x8100, first set the address: + i2c_smbus_write_byte_data(fd, 0x81, 0x00); + +And then read the data + value = i2c_smbus_read_byte(fd); + + or + + count = i2c_smbus_read_i2c_block_data(fd, 0x84, 16, buffer); + +The block read should read 16 bytes. +0x84 is the block read command. + +See the datasheet for more details. + |