regulators: Improve docs for compare_vpd
Improve the documentation for the compare_vpd JSON action:
* Explain what "VPD" is
* Provide an example use case
Signed-off-by: Shawn McCarney <shawnmm@us.ibm.com>
Change-Id: Iafb3e47293c678a2ea6923438253e2c60f35e8e2
diff --git a/phosphor-regulators/docs/config_file/compare_vpd.md b/phosphor-regulators/docs/config_file/compare_vpd.md
index e87ef87..1c2b924 100644
--- a/phosphor-regulators/docs/config_file/compare_vpd.md
+++ b/phosphor-regulators/docs/config_file/compare_vpd.md
@@ -3,12 +3,20 @@
## Description
Compares a VPD (Vital Product Data) keyword value to an expected value.
-The following keywords are currently supported:
+VPD is information that describes a hardware component. VPD is typically read
+from an EEPROM on a Field-Replaceable Unit (FRU). For this reason, VPD is also
+called "FRU data".
+
+The following VPD keywords are currently supported:
* CCIN
* Manufacturer
* Model
* PartNumber
+This action can be used in an [if](if.md) condition to execute actions based on
+a VPD keyword value. For example, you could set the output voltage only for
+regulators with a specific Model number.
+
## Properties
| Name | Required | Type | Description |
| :--- | :------: | :--- | :---------- |