Advanced Configuration and Power Interface Specification

Advanced Configuration and Power Interface Specification
length of the request data buffer. Afterwards, this value represents the length of the result
response data buffer.
• Data (bytes 65-2) represents a 64-byte buffer, and is the location where actual data is stored.
Before the operation is carried out, this represents the actual request message payload.
Afterwards, this represents the response message payload as returned by the IPMI command.
For example, the following ASL shows the use of the IPMI data buffer to carry out a command for a
power function. This code is based on the example ASL presented in Section 5.5.2.4.3.1, “Declaring
IPMI Fields,” which lists the operation region and field definitions for relevant IPMI power
metering commands.
/* Create the IPMI data buffer */
Name(BUFF, Buffer(66){})
// Create IPMI data buffer as BUFF
CreateByteField(BUFF, 0x00, STAT)
// STAT = Status (Byte)
CreateByteField(BUFF, 0x01, LENG)
// LENG = Length (Byte)
CreateByteField(BUFF, 0x02, MODE) // MODE = Mode (Byte)
CreateByteField(BUFF, 0x03, RESV)
// RESV = Reserved (Byte)
Store(0x2, LENG)
// Request message is 2 bytes long
Store(0x1, MODE) // Set Mode to 1
Store(Store(BUFF, GPMM), BUFF)
CreateByteField(BUFF, 0x02, CMPC)
CreateWordField(BUFF, 0x03, APOW)
// Write the request into the GPMM command,
// then read the results
// CMPC = Completion code (Byte)
// APOW = Average power measurement (Word)
If(LAnd(LEqual(STAT, 0x0), LEqual(CMPC, 0x0)))
{
Return(APOW)
}
Else
{
Return(Ones)
}
// Successful?
// Return the average power measurement
// Return invalid
Notice the use of the CreateField primitives to access the data buffer’s sub-elements (Status,
Length, and Data), where Data (bytes 65-2) is ‘typecast’ into different fields (including the result
completion code).
The example above demonstrates the use of the Store() operator and the bi-directional data buffer to
invoke the actual IPMI command represented by the virtual register. The inner Store() writes the
request message data buffer to the IPMI operation region handler, and invokes the command. The
outer Store() takes the result of that command and writes it back into the data buffer, this time
representing the response message.
5.5.2.4.3.3 IPMI Status Code
Every IPMI command results in a status code returned as the first byte of the response message,
contained in the bi-directional data buffer. This status code can indicate success, various errors, and
possibly timeout from the IPMI operation handler. This is necessary because it is possible for certain
IPMI commands to take up to 5 seconds to carry out, and since an AML Store() operation is
synchronous by nature, it is essential to make sure the IPMI operation returns in a timely fashion so
as not to block the AML interpreter in the OSPM.
226 April, 2015 Version 6.0