Copyright 2018 IBM

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

Introduction

This document defines a protocol and several transports for flash access mediation between the host and the Baseboard Management Controller (BMC).

The driving motivation for the protocol is to expose flash devices owned by the BMC to the host. Usually, the flash device of interest is the host's firmware flash device - in some platform designs this is owned by the BMC to enable lights-out updates of the host firmware.

As the flash is owned by the BMC, access by the host to its firmware must be abstracted and mediated. Abstraction and mediation alleviates several problems:

1. Proliferation of flash controller driver implementations throughout firmware
2. Conflict of access between the host and the BMC to the flash controller
3. In some circumstances, mitigates security concerns.

The protocol introduced in this document addresses each of these issues. Specifically, the document addresses defining a control mechanism for exposing flash data in the LPC firmware space, communicated via functions in the LPC IO space.

Scope

The scope of the document is limited to defining the protocol and its transports, and does not cover the content or structure of the data read or written to the flash by the host firmware.

The definition of transport-specific parameters, for example selection of IPMI (NetFn, Command) pairs, is also beyond the scope of the document.

Background, Design and Constraints

The protocol was developed to meet requirements on OpenPOWER systems based around the ASPEED BMC System-on-Chips such as the AST2400 and AST2500. The ASPEED BMCs have properties and features that need to be taken into account:

1. A read-only mapping of the SPI flash devices onto the ARM core's AHB
2. Remapping of LPC Firmware cycles onto the AHB (LPC2AHB bridge)
3. A reasonable but not significant amount of attached DRAM

Prior to the development of the protocol described below flash reads were serviced by pointing the LPC2AHB bridge at the read-only flash mapping, and writes were serviced by a separate bridge that suffers significant performance and security issues.

Point 3 serves to justify some of the design decisions embodied in the protocol, mainly the complexity required by the flexibility to absorb as much or as little reserved memory as desired via the concept of BMC-controlled windowing.

The core concept of the protocol moves access away from the naive routing of LPC firmware cycles onto the host firmware SPI flash AHB mapping, and concentrates on servicing the LPC firmware cycles from reserved system memory. As the memory backing the LPC2AHB mapping is now writable the protocol meets the host's write requirements by defining commands to open, dirty and flush an in-memory window representing the state of the flash. The mechanism to read the flash becomes same as write, just that the dirty and flush commands are not legal on such windows.

Historic and Future Naming

The original transport for the protocol was the ASPEED BMC LPC mailbox interface, and previous revisions of the protocol documentation referred to the protocol as the "mailbox" or "mbox" protocol. This naming is now deprecated, as the protocol has grown further transports and naming the protocol by its transport rather than its intent was, on reflection, misguided.

The protocol has been tentatively renamed to the "Host I/O Mapping Protocol" or "hiomap". This is a reflection of its true purpose - to control the host's view of data exposed from the BMC.

Protocol Overview

The primary flow of the protocol is for the host to send requests to the BMC, which adjusts the mapping of the LPC firmware space as requested and returns a status response to the host. These interactions are labelled "commands". However, as there is now an active software component on the BMC consuming access requests, the BMC must occasionally indicate state changes to the host. Such interactions are labelled "events". For example, if a user or other system software on the BMC suspends the host's access to its flash device, the BMC-side daemon implementing the protocol must notify the host that its requests will be denied until further notice.

Protocol Versioning

To enable evolution of the command and event interfaces, incremental changes to the behaviour are defined in new versions of the protocol. The descriptions and tables that follow all identify the versions to which they are applicable.

The highest currently specified protocol version is version 3.

Table of Commands

ID	Name	v1	v2	v3	Description
1	RESET	✓	✓	✓	Reset the state of the LPC firmware space, closing any active window
2	GET_INFO	✓	✓	✓	Perform protocol version negotiation and retrieve fundamental parameters
3	GET_FLASH_INFO	✓	✓	✓	Retrieve flash-specific parameters
4	CREATE_READ_WINDOW	✓	✓	✓	Request mapping of a flash region for read
5	CLOSE	✓	✓	✓	Close the current window, flushing any dirty regions
6	CREATE_WRITE_WINDOW	✓	✓	✓	Request mapping of a flash region for write
7	MARK_DIRTY	✓	✓	✓	Mark a region of a write window as modified
8	FLUSH	✓	✓	✓	Flush dirty regions of the write window to flash
9	ACK	✓	✓	✓	Acknowledge the receipt of an event from the BMC
10	ERASE		✓	✓	Mark a region of a write window as erased
11	GET_FLASH_NAME			✓	Retrieve the name of an indexed flash device
12	LOCK			✓	Mark a region of the current flash window as immutable

Table of Events

ID	Name	v1	v2	v3	Description
0	PROTOCOL_RESET	✓	✓	✓	The host is required to perform version negotiation and re-establish its window of interest
1	WINDOW_RESET		✓	✓	The host must re-establish its window of interest
6	FLASH_CONTROL_LOST		✓	✓	The host should suspend access requests
7	DAEMON_READY		✓	✓	The daemon is active and can accept commands

List of Transports

An essential feature of the protocol is that its behaviour is independent of the host-BMC transport. The command and event interfaces of each transport necessarily reflect the version of the protocol they are implementing, but the transport has no influence otherwise.

There are three documented transports for the protocol:

1. The ASPEED BMC LPC Mailbox transport
2. The IPMI transport
3. The DBus transport

The command layout, routing and event mechanism for each transport all have different features and are detailed below. An important note is that command design is limited by the most constrained transport - the LPC mailbox transport - where only 11 bytes are available for encoding of command parameters.

Implementations must choose to support one or more of the transports outlined in this document.

Note that the DBus transport is intended for BMC-internal communications, and can be used to separate a host-interface transport from the protocol implementation.

Protocol Flow

The high-level protocol flow is that the host first issues a GET_INFO command to negotiate the protocol version and acquire parameters fundamental to constructing arguments to and interpreting responses from the commands that follow.

Once GET_INFO has successfully completed, the host should request the flash parameters with GET_FLASH_INFO. The response provides information on the flash capacity and the size of its erase granule.

Following GET_FLASH_INFO, the next act is to establish an active flash window with either one of the CREATE_READ_WINDOW or CREATE_WRITE_WINDOW commands.

In the event of creating a write window the host must inform the BMC of the regions to which it has written with MARK_DIRTY- the BMC receives no notification of accesses from the host, they are simply mapped by the LPC2AHB bridge as necessary. As the accesses are to system memory and not the flash the changes identified by the MARK_DIRTY commands are not permanent until a FLUSH command is received (implicit flushes are discussed below), at which point the dirty regions of the active window will be written to the flash device.

As an optimisation the host may choose to use the ERASE command to indicate that large regions should be set to the erased state. This optimisation saves the associated LPC firmware cycles to write the regions into the erased state.

Version Negotiation

When invoking GET_INFO the host must provide the BMC its highest supported version of the protocol. The BMC must respond with a protocol version less than or equal to that requested by the host, or in the event that there is no such value, an error code. In the event that an error is returned the host must not continue to communicate with the BMC. Otherwise, the protocol version returned by the BMC is the agreed protocol version for all further communication. The host may at a future point request a change in protocol version by issuing a subsequent GET_INFO command.

Unversioned Commands

In some circumstances it is necessary for bootstrap or optimisation purposes to support unversioned commands. The protocol supports three unversioned commands:

1. RESET
2. GET_INFO
3. ACK

All remaining commands have their presence and behaviour specified with respect to the negotiated version of the protocol.

The arguments to the GET_INFO command are considered unversioned and as a result are static in nature - the protocol implementation has no means to decode version-specific arguments as the version has not yet been negotiated. With respect to the response, the version field is unversioned, but all subsequent fields may be versioned.

RESET remaining unversioned is an optimisation catering to deeply embedded components on the host side that may need access to the command. Keeping RESET unversioned removes the complexity of implementing GET_INFO with its version negotiation and minimises the overhead required to get into the pre-boot state.

Defining ACK as unversioned ensures host firmware that has minimal protocol support can silence interrupts from the BMC as required.

Sequence Numbers

Sequence numbers are included in messages for correlation of commands and responses. v1, v2 and v3 of the protocol permit either zero or one commands to be in progress (yet to receive a response).

For generality, the host must generate a sequence number that is unique with respect to the previous command (one that has received a response) and any in-progress commands. Sequence numbers meeting this requirement are considered valid. The BMC's response to a command must contain the same sequence number issued by the host as found in the relevant command.

Sequence numbers may be reused in accordance with the constraints outlined above. However, it is not an error if the BMC receives a unversioned command (RESET, GET_INFO or ACK) with an invalid sequence number. For all other cases, the BMC must respond with an error if the constraints are violated. If the host receives a sequence-related error response it must consider any in-progress commands to have failed. The host may retry the affected command(s) after generating a suitable sequence number.

Window Management

There is only ever one active window which is the window created by the most recent CREATE_READ_WINDOW or CREATE_WRITE_WINDOW call which succeeded. Even though there are two types of windows there can still only be one active window irrespective of type. The host must not write to a read window. The host may read from a write window and the BMC must guarantee that the window reflects what the host has written there.

A window can be closed by issuing the CLOSE command, in which case there is no active window and the host must not access the LPC firmware space until a window is subsequently opened. If the host closes an active write window then the BMC must perform an implicit flush. If the host tries to open a new window with an already active window then the active window is closed (and implicitly flushed if it was a write window). If the new window is successfully opened then it is the new active window; if the command fails then there is no active window and the previously active window must no longer be accessed.

The host must not access an LPC address other than that which is contained by the active window. The host must not use write management functions (see below) if the active window is a read window or if there is no active window.

Command Parameter Types

It is common in the protocol definition for command parameters to be represented in terms of a block size. This block size may refer to e.g. the size of the erase granule of the flash, or it may be another value entirely. Regardless of what it represents, the argument values are scaled by the block size determined by version negotiation. Specifying arguments in terms of a block size allows transports to keep a compact representation in constrained implementations such as the LPC mailbox transport.

Note that for simplicity block size must always be a power-of-2. The block size must also be greater than or equal to 4K regardless of the negotiated protocol version.

Finally, conversion between blocks and bytes is achieved by respectively dividing or multiplying the quantity by the negotiated block-size.

Transport Overview

Several transports are defined for the protocol and are outlined below. The key features of transport support are the wire-format, delivery mechanisms of commands and events, and the definition and delivery of response codes.

The DBus transport is the most foreign of the three as it does not encode the command index or a sequence number; these two elements are handled by the properties of DBus itself.

Mailbox Transport

• Multi-byte quantity endianness: Little-endian
• Command length encoding: Assumed from negotiated protocol version
• Parameter alignment: Packed (no padding)
• Command status response: ABI-defined Response byte
• Event Delivery: ABI-defined BMC Status byte

The mailbox transport defines the ABI used over the mailbox registers. There are 16 data registers and several status and control registers for managing interrupts between the host and the BMC. For the purpose of defining the transport ABI the status and control registers can mostly be disregarded, save for the necessity of issuing and responding to interrupts on each side.

Assuming the registers are in a contiguous layout (this is not reflected in the hardware, but may be the abstraction presented by the associated kernel driver), the ABI is defined as follows, where the bytes in the range [2, 12] are available for command parameters and are defined on a per-command basis.

    0        7         15                    31
   +----------+----------+---------------------+
 0 | Command  | Sequence |                     |
   +----------+----------+---------------------+
 4 |                                           |
   +-------------------------------------------+
 8 |                                           |
   +----------+----------+----------+----------+
12 |          | Response |  BMC Sts | Host Sts |
   +----------+----------+----------+----------+
    0        7         15         23         31

Command status response codes are as follows:

Status Codes

ID	Name	v1	v2	v3	Description
1	SUCCESS	✓	✓	✓	Command completed successfully
2	PARAM_ERROR	✓	✓	✓	Error with parameters supplied or command invalid
3	WRITE_ERROR	✓	✓	✓	Error writing to the backing file system
4	SYSTEM_ERROR	✓	✓	✓	Error in BMC performing system action
5	TIMEOUT	✓	✓	✓	Timeout in performing action
6	BUSY		✓	✓	Flash access suspended, retry later
7	WINDOW_ERROR		✓	✓	Invalid window state or command invalid for window
8	SEQ_ERROR		✓	✓	Invalid sequence number supplied with command
9	LOCKED_ERROR			✓	Erased or dirtied region intersected a locked region

IPMI Transport

• Multi-byte quantity endianness: Little-endian
• Command length encoding: Assumed from negotiated protocol version
• Parameter alignment: Packed (no padding)
• Command status response: Mapped to IPMI completion codes
• Event Delivery: Status byte in SEL via SMS_ATN

The IPMI transport must reserve one (NetFn, Command) pair for host-to-BMC communications and one SEL (NetFn, Command) pair for BMC-to-host communication, signaled by SMS_ATN.

The wire command framing is as follows:

1. The command identifier is the first value and is encoded in one byte
2. The sequence number is the second value and is encoded in one byte
3. Parameters required by the (version, command) pair follow

    0        7         15                     N
   +----------+----------+---------     -------+
 0 | Command  | Sequence |          ...        |
   +----------+----------+---------     -------+

DBus Transport

• Multi-byte quantity endianness: Transport encoded
• Command length encoding: Transport encoded
• Parameter alignment: Transport encoded
• Command status response: Mapped to Unix system error codes
• Event Delivery: DBus signals and properties per event type

DBus defines its own wire-format for messages, and so support for this transport concentrates on mapping commands and events onto DBus concepts. Specifically, commands are represented by DBus methods and events are represented by properties. DBus will automatically generate a PropertiesChanged signal for changes to properties allowing consumers to learn of updates as they happen.

As the commands are represented by DBus methods there is no need to encode the command index in the request - this is represented by the appropriate method on the implementation object's interface.

Similarly, there's no need to encode sequence numbers as DBus handles the correlation of messages over the bus. As there is no encoding of sequence numbers, there is no need to describe a command status response like SEQ_ERROR, which allows a clean mapping to Unix error codes.

Finally, commands mapped to methods have the number of parameters and types described by the method's type signature, though these descriptions concern the basic wire types and not the semantic types relevant to the protocol. The method type signature and parameter ordering are described in the relevant command definition.

Command Definitions

The command identifier values and command-response parameter formats are described in tables under headers for each command. The order of the parameters in the parameter tables reflects the order of the parameters in the commands and responses. The M, I, and D columns represent the Mailbox, IPMI and DBus transports respectively. For the command identifier table the value in these columns' cells represent the command index, or for DBus, its method name. For the parameter tables the value represent the parameter's offset in the message (disregarding the command and sequence bytes), or in the case of DBus the appropriate type signature.

RESET Command

v1	v2	v3	M	I	D
✓	✓	✓	1	1	Reset

v1 Parameters

Parameter	Unit	Size	M	I	D

Parameter	Unit	Size	M	I	D

v2 Parameters

Parameter	Unit	Size	M	I	D

Parameter	Unit	Size	M	I	D

v3 Parameters

Parameter	Unit	Size	M	I	D

Parameter	Unit	Size	M	I	D

Description

Requests the BMC return the LPC firmware space to a state ready for host firmware bootstrap.

GET_INFO Command

v1	v2	v3	M	I	D
✓	✓	✓	2	2	GetInfo

v1 Parameters

Parameter	Unit	Size	M	I	D
Version	Version	1	0	0	y

Parameter	Unit	Size	M	I	D
Version	Version	1	0	0	y
Read Window Size	Blocks	2	1	1	q
Write Window Size	Blocks	2	3	3	q

v2 Parameters

Parameter	Unit	Size	M	I	D
Version	Version	1	0	0	y

Parameter	Unit	Size	M	I	D
Version	Version	1	0	0	y
Block Size Shift	Count	1	5	1	y
Timeout	Seconds	2	6	2	q

v3 Parameters

Parameter	Unit	Size	M	I	D
Version	Version	1	0	0	y
Block Size Shift	Count	1	1	1	y

Parameter	Unit	Size	M	I	D
Version	Version	1	0	0	y
Block Size Shift	Count	1	5	1	y
Timeout	Seconds	2	6	2	q
Devices	Count	1	8	4	y

Description

The suggested timeout is a hint to the host as to how long it should wait after issuing a command to the BMC before it times out waiting for a response. This is the maximum time which the BMC thinks it could take to service any command which the host could issue. This may be set to zero to indicate that the BMC does not wish to provide a hint in which case the host must choose some reasonable value.

From v3 the host may desire a specific block size and thus can request this by giving a hint to the daemon (may be zero). The daemon may use this to select the block size which it will use however is free to ignore it. The value in the response is the block size which must be used for all further requests until a new size is negotiated by another call to GET_INFO.

GET_FLASH_INFO Command

v1	v2	v3	M	I	D
✓	✓	✓	3	3	GetFlashInfo

v1 Parameters

Parameter	Unit	Size	M	I	D

Parameter	Unit	Size	M	I	D
Flash Size	Bytes	4	0	0	u
Erase Granule	Bytes	4	4	4	u

v2 Parameters

Parameter	Unit	Size	M	I	D

Parameter	Unit	Size	M	I	D
Flash Size	Blocks	2	0	0	q
Erase Granule	Blocks	2	2	2	q

v3 Parameters

Parameter	Unit	Size	M	I	D
Device ID	Index	1	0	0	y

Parameter	Unit	Size	M	I	D
Flash Size	Blocks	2	0	0	q
Erase Granule	Blocks	2	2	2	q

CREATE_READ_WINDOW Command

v1	v2	v3	M	I	D
✓	✓	✓	4	4	CreateReadWindow

v1 Parameters

Parameter	Unit	Size	M	I	D
Flash Offset	Blocks	2	0	0	q

Parameter	Unit	Size	M	I	D
LPC FW Offset	Blocks	2	0	0	q

v2 Parameters

Parameter	Unit	Size	M	I	D
Flash Address	Blocks	2	0	0	q
Length	Blocks	2	2	2	q

Parameter	Unit	Size	M	I	D
LPC FW Address	Blocks	2	0	0	q
Length	Blocks	2	2	2	q
Flash Address	blocks	2	4	4	q

v3 Parameters

Parameter	Unit	Size	M	I	D
Flash Address	Blocks	2	0	0	q
Length	Blocks	2	2	2	q
Device ID	Index	1	4	4	y

Parameter	Unit	Size	M	I	D
LPC FW Address	Blocks	2	0	0	q
Length	Blocks	2	2	2	q
Flash Address	blocks	2	4	4	q

Description

The flash offset which the host requests access to is always taken from the start of flash - that is it is an absolute offset into flash.

LPC bus address is always given from the start of the LPC address space - that is it is an absolute address.

The requested access size is only a hint. The response indicates the actual size of the window. The BMC may want to use the requested size to pre-load the remainder of the request. The host must not access past the end of the active window.

The flash offset mapped by the window is an absolute flash offset and must be less than or equal to the flash offset requested by the host. It is the responsibility of the host to use this information to access any offset which is required.

The requested window size may be zero. In this case the BMC is free to create any sized window but it must contain at least the first block of data requested by the host. A large window is of course preferred and should correspond to the default size returned in the GET_INFO command.

If this command returns successfully then the created window is the active window. If it fails then there is no active window.

CLOSE Command

v1	v2	v3	M	I	D
✓	✓	✓	5	5	Close

v1 Parameters

Parameter	Unit	Size	M	I	D

Parameter	Unit	Size	M	I	D

v2 Parameters

Parameter	Unit	Size	M	I	D
Flags	Field	1	0	0	y

Parameter	Unit	Size	M	I	D

v3 Parameters

Parameter	Unit	Size	M	I	D
Flags	Field	1	0	0	y

Parameter	Unit	Size	M	I	D

Description

Closes the active window. Any further access to the LPC bus address specified to address the previously active window will have undefined effects. If the active window is a write window then the BMC must perform an implicit flush.

The Flags argument allows the host to provide some hints to the BMC. Defined values are:

0x01 - Short Lifetime:
       The window is unlikely to be accessed anytime again in the near future.
       The effect of this will depend on BMC implementation. In the event that
       the BMC performs some caching the BMC daemon could mark data contained
       in a window closed with this flag as first to be evicted from the cache.

CREATE_WRITE_WINDOW Command

v1	v2	v3	M	I	D
✓	✓	✓	6	6	CreateWriteWindow

v1 Parameters

Parameter	Unit	Size	M	I	D
Flash Offset	Blocks	2	0	0	q

Parameter	Unit	Size	M	I	D
LPC FW Offset	Blocks	2	0	0	q

v2 Parameters

Parameter	Unit	Size	M	I	D
Flash Address	Blocks	2	0	0	q
Length	Blocks	2	2	2	q

Parameter	Unit	Size	M	I	D
LPC FW Address	Blocks	2	0	0	q
Length	Blocks	2	2	2	q
Flash Address	blocks	2	4	4	q

v3 Parameters

Parameter	Unit	Size	M	I	D
Flash Address	Blocks	2	0	0	q
Length	Blocks	2	2	2	q
Device ID	Index	1	4	4	y

Parameter	Unit	Size	M	I	D
LPC FW Address	Blocks	2	0	0	q
Length	Blocks	2	2	2	q
Flash Address	blocks	2	4	4	q

Description

The flash offset which the host requests access to is always taken from the start of flash - that is it is an absolute offset into flash.

LPC bus address is always given from the start of the LPC address space - that is it is an absolute address.

The requested access size is only a hint. The response indicates the actual size of the window. The BMC may want to use the requested size to pre-load the remainder of the request. The host must not access past the end of the active window.

The flash offset mapped by the window is an absolute flash offset and must be less than or equal to the flash offset requested by the host. It is the responsibility of the host to use this information to access any offset which is required.

The requested window size may be zero. In this case the BMC is free to create any sized window but it must contain at least the first block of data requested by the host. A large window is of course preferred and should correspond to the default size returned in the GET_INFO command.

If this command returns successfully then the created window is the active window. If it fails then there is no active window.

MARK_DIRTY Command

v1	v2	v3	M	I	D
✓	✓	✓	7	7	MarkDirty

v1 Parameters

Parameter	Unit	Size	M	I	D
Flash Offset	Blocks	2	0	0	q
Length	Bytes	4	2	2	u

Parameter	Unit	Size	M	I	D

v2 Parameters

Parameter	Unit	Size	M	I	D
Window Offset	Blocks	2	0	0	q
Length	Blocks	2	2	2	q

Parameter	Unit	Size	M	I	D

v3 Parameters

Parameter	Unit	Size	M	I	D
Window Offset	Blocks	2	0	0	q
Length	Blocks	2	2	2	q
Flags	Field	1	4	4	y

Parameter	Unit	Size	M	I	D

Description

The BMC has no method for intercepting writes that occur over the LPC bus. The host must explicitly notify the daemon of where and when a write has occurred so it can be flushed to backing storage.

Offsets are given as an absolute (either into flash (V1) or the active window (V2)) and a zero offset refers to the first block. If the offset + number exceeds the size of the active window then the command must not succeed.

The host can give a hint to the daemon that is doesn't have to erase a flash area before writing to it by setting bit zero of the Flags parameter. This means that the daemon will blindly perform a write to that area and will not try to erase it before hand. This can be used if the host knows that a large area has already been erased for example but then wants to perform many small writes.

FLUSH Command

v1	v2	v3	M	I	D
✓	✓	✓	8	8	Flush

v1 Parameters

Parameter	Unit	Size	M	I	D
Flash Offset	Blocks	2	0	0	q
Length	Bytes	4	2	2	u

Parameter	Unit	Size	M	I	D

v2 Parameters

Parameter	Unit	Size	M	I	D

Parameter	Unit	Size	M	I	D

v3 Parameters

Parameter	Unit	Size	M	I	D

Parameter	Unit	Size	M	I	D

Description

Flushes any dirty/erased blocks in the active window to the backing storage.

In V1 this can also be used to mark parts of the flash dirty and flush in a single command. In V2 the explicit mark dirty command must be used before a call to flush since there are no longer any arguments. If the offset + length exceeds the size of the active window then the command must not succeed.

ACK Command

v1	v2	v3	M	I	D
✓	✓	✓	9	9	Ack

v1 Parameters

Parameter	Unit	Size	M	I	D
Ack Mask	Field	1	0	0	y

Parameter	Unit	Size	M	I	D

v2 Parameters

Parameter	Unit	Size	M	I	D
Ack Mask	Field	1	0	0	y

Parameter	Unit	Size	M	I	D

v3 Parameters

Parameter	Unit	Size	M	I	D
Ack Mask	Field	1	0	0	y

Parameter	Unit	Size	M	I	D

Description

The host should use this command to acknowledge BMC events propagated to the host.

ERASE Command

v1	v2	v3	M	I	D
	✓	✓	10	10	Erase

v2 Parameters

Parameter	Unit	Size	M	I	D
Window Offset	Blocks	2	0	0	q
Length	Blocks	2	2	2	q

Parameter	Unit	Size	M	I	D

v3 Parameters

Parameter	Unit	Size	M	I	D
Window Offset	Blocks	2	0	0	q
Length	Blocks	2	2	2	q

Parameter	Unit	Size	M	I	D

Description

This command allows the host to erase a large area without the need to individually write 0xFF repetitively.

Offset is the offset within the active window to start erasing from (zero refers to the first block of the active window) and number is the number of blocks of the active window to erase starting at offset. If the offset + number exceeds the size of the active window then the command must not succeed.

GET_FLASH_NAME Command

v1	v2	v3	M	I	D
		✓	11	11	GetFlashName

v3 Parameters

Parameter	Unit	Size	M	I	D
Device ID	Index	1	0	0	y

Parameter	Unit	Size	M	I	D
Name length	Bytes	1	0	0	-
Name	String	10	1	1	s

Description

Describes a flash with some kind of identifier useful to the host system.

The length in the response is the number of response arguments as part of the flash name field which the host should expect to have been populated.

Note that DBus encodes the string length in its string type, so the explicit length is omitted from the DBus message.

LOCK Command

v1	v2	v3	M	I	D
		✓	12	12	Lock

v3 Parameters

Parameter	Unit	Size	M	I	D
Flash Offset	Blocks	2	0	0	q
Length	Blocks	2	2	2	q
Device ID	Index	1	4	4	y

Parameter	Unit	Size	M	I	D

Description

Lock an area of flash so that the host can't mark it dirty or erased. If the requested area is within the current window and that area is currently marked dirty or erased then this command must fail.

Event Definitions

The M, I, and D columns represent the Mailbox, IPMI and DBus transports respectively. The values in the M, I or D columns represent the events' bit index in the status byte, or in the case of the DBus transport the name of the relevant property.

For the DBus interface, properties are used for all event types regardless of whether they should be acknowledged or not as part of the protocol. This ensures that state changes can be published atomically.

PROTOCOL_RESET Event

v1	v2	v3	M	I	D
✓	✓	✓	0	0	ProtocolReset

Description

Used to inform the host that a protocol reset has occurred, likely due to restarting the daemon. The host must perform protocol version negotiation again and must assume it has no active window. The host must also assume that any in-flight commands have failed.

WINDOW_RESET Event

v1	v2	v3	M	I	D
	✓	✓	1	1	WindowReset

Description

The host must assume that its active window has been closed and that it no longer has an active window. The host is not required to perform protocol version negotiation again. The host must assume that any in-flight commands have failed.

FLASH_CONTROL_LOST Event

v1	v2	v3	M	I	D
	✓	✓	6	6	FlashControlLost

Description

The BMC daemon has been suspended and thus no longer controls access to the flash (most likely because some other process on the BMC required direct access to the flash and has suspended the BMC daemon to preclude concurrent access).

The BMC daemon must clear this bit itself when it regains control of the flash (the host isn't able to clear it through an acknowledge command).

The host must not assume that the contents of the active window correctly reflect the contents of flash while this bit is set.

DAEMON_READY Event

v1	v2	v3	M	I	D
	✓	✓	7	7	DaemonReady

Description

Used to inform the host that the BMC daemon is ready to accept command requests. The host isn't able to clear this bit through an acknowledge command, the BMC daemon must clear it before it terminates (assuming it didn't terminate unexpectedly).

The host should not expect a response while this bit is not set.

Note that this bit being set is not a guarantee that the BMC daemon will respond as it or the BMC may have crashed without clearing it.