diff options
| author |   Yunhong Jiang <yunhong.jiang@intel.com> | 2015-08-04 12:17:53 -0700 |
|---|---|---|
| committer | Yunhong Jiang <yunhong.jiang@intel.com> | 2015-08-04 15:44:42 -0700 |
| commit | 9ca8dbcc65cfc63d6f5ef3312a33184e1d726e00 (patch) | |
| tree | 1c9cafbcd35f783a87880a10f85d1a060db1a563 /kernel/Documentation/misc-devices/ad525x_dpot.txt | |
| parent | 98260f3884f4a202f9ca5eabed40b1354c489b29 (diff) | |
Add the rt linux 4.1.3-rt3 as base
Import the rt linux 4.1.3-rt3 as OPNFV kvm base.
It's from git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git linux-4.1.y-rt and
the base is:
commit 0917f823c59692d751951bf5ea699a2d1e2f26a2
Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Sat Jul 25 12:13:34 2015 +0200
Prepare v4.1.3-rt3
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
We lose all the git history this way and it's not good. We
should apply another opnfv project repo in future.
Change-Id: I87543d81c9df70d99c5001fbdf646b202c19f423
Signed-off-by: Yunhong Jiang <yunhong.jiang@intel.com>
Diffstat (limited to 'kernel/Documentation/misc-devices/ad525x_dpot.txt')
| -rw-r--r-- | kernel/Documentation/misc-devices/ad525x_dpot.txt | 57 |
1 files changed, 57 insertions, 0 deletions
diff --git a/kernel/Documentation/misc-devices/ad525x_dpot.txt b/kernel/Documentation/misc-devices/ad525x_dpot.txt new file mode 100644 index 000000000..0c9413b1c --- /dev/null +++ b/kernel/Documentation/misc-devices/ad525x_dpot.txt @@ -0,0 +1,57 @@ +--------------------------------- + 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 |