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author | Ingo Molnar <mingo@elte.hu> | 2009-12-28 09:23:13 +0100 |
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committer | Ingo Molnar <mingo@elte.hu> | 2009-12-28 09:23:13 +0100 |
commit | 605c1a187f3ce82fbc243e2163c5ca8d1926df8e (patch) | |
tree | c8065a8c5606a66f81dc494ce22a5baa5e0dfe7e /Documentation/misc-devices | |
parent | 17a2a9b57a9a7d2fd8f97df951b5e63e0bd56ef5 (diff) | |
parent | ce9277fb08e6e721482f7011ca28dcd0449b197c (diff) | |
download | kernel-crypto-605c1a187f3ce82fbc243e2163c5ca8d1926df8e.tar.gz kernel-crypto-605c1a187f3ce82fbc243e2163c5ca8d1926df8e.tar.xz kernel-crypto-605c1a187f3ce82fbc243e2163c5ca8d1926df8e.zip |
Merge branch 'iommu/fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/joro/linux-2.6-iommu into x86/urgent
Diffstat (limited to 'Documentation/misc-devices')
-rw-r--r-- | Documentation/misc-devices/ad525x_dpot.txt | 57 |
1 files changed, 57 insertions, 0 deletions
diff --git a/Documentation/misc-devices/ad525x_dpot.txt b/Documentation/misc-devices/ad525x_dpot.txt new file mode 100644 index 00000000000..0c9413b1cbf --- /dev/null +++ b/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 |