diff options
| author | Mauro Carvalho Chehab <mchehab+huawei@kernel.org> | 2020-06-15 09:50:13 +0300 |
|---|---|---|
| committer | Jonathan Corbet <corbet@lwn.net> | 2020-06-19 23:05:49 +0300 |
| commit | 8a05eb89cb84eba1091bdc6baa9d0e463655779f (patch) | |
| tree | 821de190af69dd16eeed8ccc480864275f13af31 /Documentation/misc-devices/ad525x_dpot.rst | |
| parent | 3471b9f7e43d3505fcffc63d0271f13dd9246873 (diff) | |
| download | linux-8a05eb89cb84eba1091bdc6baa9d0e463655779f.tar.xz | |
docs: misc-devices/pci-endpoint-test.txt: convert to ReST
- use title markups;
- mark literal blocks.
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/1b1f4e5e57fd2065828cecc9d07afbd247349e94.1592203650.git.mchehab+huawei@kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Diffstat (limited to 'Documentation/misc-devices/ad525x_dpot.rst')
| -rw-r--r-- | Documentation/misc-devices/ad525x_dpot.rst | 57 |
1 files changed, 57 insertions, 0 deletions
diff --git a/Documentation/misc-devices/ad525x_dpot.rst b/Documentation/misc-devices/ad525x_dpot.rst new file mode 100644 index 000000000000..6483ec254520 --- /dev/null +++ b/Documentation/misc-devices/ad525x_dpot.rst @@ -0,0 +1,57 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============================= +AD525x Digital Potentiometers +============================= + +The ad525x_dpot driver exports a simple sysfs interface. This allows you to +work with the immediate resistance settings as well as update the saved startup +settings. Access to the factory programmed tolerance is also provided, but +interpretation of this settings is required by the end application according to +the specific part in use. + +Files +===== + +Each dpot device will have a set of eeprom, rdac, and tolerance files. How +many depends on the actual part you have, as will the range of allowed values. + +The eeprom files are used to program the startup value of the device. + +The rdac files are used to program the immediate value of the device. + +The tolerance files are the read-only factory programmed tolerance settings +and may vary greatly on a part-by-part basis. For exact interpretation of +this field, please consult the datasheet for your part. This is presented +as a hex file for easier parsing. + +Example +======= + +Locate the device in your sysfs tree. This is probably easiest by going into +the common i2c directory and locating the device by the i2c slave address:: + + # ls /sys/bus/i2c/devices/ + 0-0022 0-0027 0-002f + +So assuming the device in question is on the first i2c bus and has the slave +address of 0x2f, we descend (unrelated sysfs entries have been trimmed):: + + # ls /sys/bus/i2c/devices/0-002f/ + eeprom0 rdac0 tolerance0 + +You can use simple reads/writes to access these files:: + + # cd /sys/bus/i2c/devices/0-002f/ + + # cat eeprom0 + 0 + # echo 10 > eeprom0 + # cat eeprom0 + 10 + + # cat rdac0 + 5 + # echo 3 > rdac0 + # cat rdac0 + 3 |