ipmi.md: Clarification of some docs
Clarify that "OEM Set Control" can perform both Get and Set
Advise using ExternalSensor instead of nonexistent future OEM command
Advise to use BMC sensors normally, no OEM IPMI extensions needed
Signed-off-by: Josh Lehan <krellan@google.com>
Change-Id: I5dcd1b5242b9c64324dbaea8e64d96ef2114a8b1
diff --git a/ipmi.md b/ipmi.md
index 2a377a3..65139c8 100644
--- a/ipmi.md
+++ b/ipmi.md
@@ -1,16 +1,25 @@
# OEM-IPMI Commands to talk to Phosphor-pid-control
-## IPMI Command Specification
+## Sensor Data Pushing Advice
-The host needs the ability to send to the BMC, the margin information on the
-devices that it knows how to read that the BMC cannot. There is no command in
-IPMI that currently supports this use-case, therefore it will be added as an OEM
-command.
+For temperature sensors not reachable by the BMC, sensor readings can be
+pushed to the BMC from the host, by using the IPMI SDR as shared storage.
-The state of the BMC readable temperature sensors can be read through normal
-IPMI commands and is already supported.
+To do this, it is recommended that
+[ExternalSensor](https://github.com/openbmc/docs/blob/master/designs/external-sensor.md)
+be used. ExternalSensor can add virtual sensors to the IPMI SDR. The host
+can then write values to these virtual sensors, to keep them up to date. Thus,
+these sensors will become visible on the BMC, and can be used normally,
+similar to other temperature sensors already on the BMC.
-### OEM Set Control
+For temperature sensors on the BMC, including those added with
+ExternalSensor as mentioned above, these can be manipulated through
+normal IPMI commands, and are already supported. The same applies to fan RPM
+and PWM sensors. No additional OEM commands are required to use these.
+
+## IPMI OEM Command Specification
+
+### OEM Get/Set Control Mode
A host tool needs to be able to set the control of the thermal system to either
automatic or manual. When manual, the daemon will effectively wait to be told to
@@ -44,8 +53,8 @@
### OEM Get Failsafe Mode
A host tool needs to be able to read back whether a zone is in failsafe mode.
-This setting is read-only because it's dynamically determined within Swampd per
-zone.
+This setting is read-only because it's dynamically determined within
+phosphor-pid-control per zone.
Byte | Purpose | Value
---- | ------------ | ----------------------------------