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1.. SPDX-License-Identifier: GPL-2.02 3=============================4AD525x Digital Potentiometers5=============================6 7The ad525x_dpot driver exports a simple sysfs interface. This allows you to8work with the immediate resistance settings as well as update the saved startup9settings. Access to the factory programmed tolerance is also provided, but10interpretation of this settings is required by the end application according to11the specific part in use.12 13Files14=====15 16Each dpot device will have a set of eeprom, rdac, and tolerance files. How17many depends on the actual part you have, as will the range of allowed values.18 19The eeprom files are used to program the startup value of the device.20 21The rdac files are used to program the immediate value of the device.22 23The tolerance files are the read-only factory programmed tolerance settings24and may vary greatly on a part-by-part basis. For exact interpretation of25this field, please consult the datasheet for your part. This is presented26as a hex file for easier parsing.27 28Example29=======30 31Locate the device in your sysfs tree. This is probably easiest by going into32the common i2c directory and locating the device by the i2c slave address::33 34 # ls /sys/bus/i2c/devices/35 0-0022 0-0027 0-002f36 37So assuming the device in question is on the first i2c bus and has the slave38address of 0x2f, we descend (unrelated sysfs entries have been trimmed)::39 40 # ls /sys/bus/i2c/devices/0-002f/41 eeprom0 rdac0 tolerance042 43You can use simple reads/writes to access these files::44 45 # cd /sys/bus/i2c/devices/0-002f/46 47 # cat eeprom048 049 # echo 10 > eeprom050 # cat eeprom051 1052 53 # cat rdac054 555 # echo 3 > rdac056 # cat rdac057 358