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-
- The Linux IPMI Driver
- ---------------------
- Corey Minyard
- <minyard@mvista.com>
- <minyard@acm.org>
-
-The Intelligent Platform Management Interface, or IPMI, is a
-standard for controlling intelligent devices that monitor a system.
-It provides for dynamic discovery of sensors in the system and the
-ability to monitor the sensors and be informed when the sensor's
-values change or go outside certain boundaries. It also has a
-standardized database for field-replaceable units (FRUs) and a watchdog
-timer.
-
-To use this, you need an interface to an IPMI controller in your
-system (called a Baseboard Management Controller, or BMC) and
-management software that can use the IPMI system.
-
-This document describes how to use the IPMI driver for Linux. If you
-are not familiar with IPMI itself, see the web site at
-http://www.intel.com/design/servers/ipmi/index.htm. IPMI is a big
-subject and I can't cover it all here!
-
-Configuration
--------------
-
-The Linux IPMI driver is modular, which means you have to pick several
-things to have it work right depending on your hardware. Most of
-these are available in the 'Character Devices' menu then the IPMI
-menu.
-
-No matter what, you must pick 'IPMI top-level message handler' to use
-IPMI. What you do beyond that depends on your needs and hardware.
-
-The message handler does not provide any user-level interfaces.
-Kernel code (like the watchdog) can still use it. If you need access
-from userland, you need to select 'Device interface for IPMI' if you
-want access through a device driver.
-
-The driver interface depends on your hardware. If your system
-properly provides the SMBIOS info for IPMI, the driver will detect it
-and just work. If you have a board with a standard interface (These
-will generally be either "KCS", "SMIC", or "BT", consult your hardware
-manual), choose the 'IPMI SI handler' option. A driver also exists
-for direct I2C access to the IPMI management controller. Some boards
-support this, but it is unknown if it will work on every board. For
-this, choose 'IPMI SMBus handler', but be ready to try to do some
-figuring to see if it will work on your system if the SMBIOS/APCI
-information is wrong or not present. It is fairly safe to have both
-these enabled and let the drivers auto-detect what is present.
-
-You should generally enable ACPI on your system, as systems with IPMI
-can have ACPI tables describing them.
-
-If you have a standard interface and the board manufacturer has done
-their job correctly, the IPMI controller should be automatically
-detected (via ACPI or SMBIOS tables) and should just work. Sadly,
-many boards do not have this information. The driver attempts
-standard defaults, but they may not work. If you fall into this
-situation, you need to read the section below named 'The SI Driver' or
-"The SMBus Driver" on how to hand-configure your system.
-
-IPMI defines a standard watchdog timer. You can enable this with the
-'IPMI Watchdog Timer' config option. If you compile the driver into
-the kernel, then via a kernel command-line option you can have the
-watchdog timer start as soon as it initializes. It also have a lot
-of other options, see the 'Watchdog' section below for more details.
-Note that you can also have the watchdog continue to run if it is
-closed (by default it is disabled on close). Go into the 'Watchdog
-Cards' menu, enable 'Watchdog Timer Support', and enable the option
-'Disable watchdog shutdown on close'.
-
-IPMI systems can often be powered off using IPMI commands. Select
-'IPMI Poweroff' to do this. The driver will auto-detect if the system
-can be powered off by IPMI. It is safe to enable this even if your
-system doesn't support this option. This works on ATCA systems, the
-Radisys CPI1 card, and any IPMI system that supports standard chassis
-management commands.
-
-If you want the driver to put an event into the event log on a panic,
-enable the 'Generate a panic event to all BMCs on a panic' option. If
-you want the whole panic string put into the event log using OEM
-events, enable the 'Generate OEM events containing the panic string'
-option.
-
-Basic Design
-------------
-
-The Linux IPMI driver is designed to be very modular and flexible, you
-only need to take the pieces you need and you can use it in many
-different ways. Because of that, it's broken into many chunks of
-code. These chunks (by module name) are:
-
-ipmi_msghandler - This is the central piece of software for the IPMI
-system. It handles all messages, message timing, and responses. The
-IPMI users tie into this, and the IPMI physical interfaces (called
-System Management Interfaces, or SMIs) also tie in here. This
-provides the kernelland interface for IPMI, but does not provide an
-interface for use by application processes.
-
-ipmi_devintf - This provides a userland IOCTL interface for the IPMI
-driver, each open file for this device ties in to the message handler
-as an IPMI user.
-
-ipmi_si - A driver for various system interfaces. This supports KCS,
-SMIC, and BT interfaces. Unless you have an SMBus interface or your
-own custom interface, you probably need to use this.
-
-ipmi_smb - A driver for accessing BMCs on the SMBus. It uses the
-I2C kernel driver's SMBus interfaces to send and receive IPMI messages
-over the SMBus.
-
-ipmi_watchdog - IPMI requires systems to have a very capable watchdog
-timer. This driver implements the standard Linux watchdog timer
-interface on top of the IPMI message handler.
-
-ipmi_poweroff - Some systems support the ability to be turned off via
-IPMI commands.
-
-These are all individually selectable via configuration options.
-
-Note that the KCS-only interface has been removed. The af_ipmi driver
-is no longer supported and has been removed because it was impossible
-to do 32 bit emulation on 64-bit kernels with it.
-
-Much documentation for the interface is in the include files. The
-IPMI include files are:
-
-net/af_ipmi.h - Contains the socket interface.
-
-linux/ipmi.h - Contains the user interface and IOCTL interface for IPMI.
-
-linux/ipmi_smi.h - Contains the interface for system management interfaces
-(things that interface to IPMI controllers) to use.
-
-linux/ipmi_msgdefs.h - General definitions for base IPMI messaging.
-
-
-Addressing
-----------
-
-The IPMI addressing works much like IP addresses, you have an overlay
-to handle the different address types. The overlay is:
-
- struct ipmi_addr
- {
- int addr_type;
- short channel;
- char data[IPMI_MAX_ADDR_SIZE];
- };
-
-The addr_type determines what the address really is. The driver
-currently understands two different types of addresses.
-
-"System Interface" addresses are defined as:
-
- struct ipmi_system_interface_addr
- {
- int addr_type;
- short channel;
- };
-
-and the type is IPMI_SYSTEM_INTERFACE_ADDR_TYPE. This is used for talking
-straight to the BMC on the current card. The channel must be
-IPMI_BMC_CHANNEL.
-
-Messages that are destined to go out on the IPMB bus use the
-IPMI_IPMB_ADDR_TYPE address type. The format is
-
- struct ipmi_ipmb_addr
- {
- int addr_type;
- short channel;
- unsigned char slave_addr;
- unsigned char lun;
- };
-
-The "channel" here is generally zero, but some devices support more
-than one channel, it corresponds to the channel as defined in the IPMI
-spec.
-
-
-Messages
---------
-
-Messages are defined as:
-
-struct ipmi_msg
-{
- unsigned char netfn;
- unsigned char lun;
- unsigned char cmd;
- unsigned char *data;
- int data_len;
-};
-
-The driver takes care of adding/stripping the header information. The
-data portion is just the data to be send (do NOT put addressing info
-here) or the response. Note that the completion code of a response is
-the first item in "data", it is not stripped out because that is how
-all the messages are defined in the spec (and thus makes counting the
-offsets a little easier :-).
-
-When using the IOCTL interface from userland, you must provide a block
-of data for "data", fill it, and set data_len to the length of the
-block of data, even when receiving messages. Otherwise the driver
-will have no place to put the message.
-
-Messages coming up from the message handler in kernelland will come in
-as:
-
- struct ipmi_recv_msg
- {
- struct list_head link;
-
- /* The type of message as defined in the "Receive Types"
- defines above. */
- int recv_type;
-
- ipmi_user_t *user;
- struct ipmi_addr addr;
- long msgid;
- struct ipmi_msg msg;
-
- /* Call this when done with the message. It will presumably free
- the message and do any other necessary cleanup. */
- void (*done)(struct ipmi_recv_msg *msg);
-
- /* Place-holder for the data, don't make any assumptions about
- the size or existence of this, since it may change. */
- unsigned char msg_data[IPMI_MAX_MSG_LENGTH];
- };
-
-You should look at the receive type and handle the message
-appropriately.
-
-
-The Upper Layer Interface (Message Handler)
--------------------------------------------
-
-The upper layer of the interface provides the users with a consistent
-view of the IPMI interfaces. It allows multiple SMI interfaces to be
-addressed (because some boards actually have multiple BMCs on them)
-and the user should not have to care what type of SMI is below them.
-
-
-Creating the User
-
-To user the message handler, you must first create a user using
-ipmi_create_user. The interface number specifies which SMI you want
-to connect to, and you must supply callback functions to be called
-when data comes in. The callback function can run at interrupt level,
-so be careful using the callbacks. This also allows to you pass in a
-piece of data, the handler_data, that will be passed back to you on
-all calls.
-
-Once you are done, call ipmi_destroy_user() to get rid of the user.
-
-From userland, opening the device automatically creates a user, and
-closing the device automatically destroys the user.
-
-
-Messaging
-
-To send a message from kernel-land, the ipmi_request() call does
-pretty much all message handling. Most of the parameter are
-self-explanatory. However, it takes a "msgid" parameter. This is NOT
-the sequence number of messages. It is simply a long value that is
-passed back when the response for the message is returned. You may
-use it for anything you like.
-
-Responses come back in the function pointed to by the ipmi_recv_hndl
-field of the "handler" that you passed in to ipmi_create_user().
-Remember again, these may be running at interrupt level. Remember to
-look at the receive type, too.
-
-From userland, you fill out an ipmi_req_t structure and use the
-IPMICTL_SEND_COMMAND ioctl. For incoming stuff, you can use select()
-or poll() to wait for messages to come in. However, you cannot use
-read() to get them, you must call the IPMICTL_RECEIVE_MSG with the
-ipmi_recv_t structure to actually get the message. Remember that you
-must supply a pointer to a block of data in the msg.data field, and
-you must fill in the msg.data_len field with the size of the data.
-This gives the receiver a place to actually put the message.
-
-If the message cannot fit into the data you provide, you will get an
-EMSGSIZE error and the driver will leave the data in the receive
-queue. If you want to get it and have it truncate the message, us
-the IPMICTL_RECEIVE_MSG_TRUNC ioctl.
-
-When you send a command (which is defined by the lowest-order bit of
-the netfn per the IPMI spec) on the IPMB bus, the driver will
-automatically assign the sequence number to the command and save the
-command. If the response is not receive in the IPMI-specified 5
-seconds, it will generate a response automatically saying the command
-timed out. If an unsolicited response comes in (if it was after 5
-seconds, for instance), that response will be ignored.
-
-In kernelland, after you receive a message and are done with it, you
-MUST call ipmi_free_recv_msg() on it, or you will leak messages. Note
-that you should NEVER mess with the "done" field of a message, that is
-required to properly clean up the message.
-
-Note that when sending, there is an ipmi_request_supply_msgs() call
-that lets you supply the smi and receive message. This is useful for
-pieces of code that need to work even if the system is out of buffers
-(the watchdog timer uses this, for instance). You supply your own
-buffer and own free routines. This is not recommended for normal use,
-though, since it is tricky to manage your own buffers.
-
-
-Events and Incoming Commands
-
-The driver takes care of polling for IPMI events and receiving
-commands (commands are messages that are not responses, they are
-commands that other things on the IPMB bus have sent you). To receive
-these, you must register for them, they will not automatically be sent
-to you.
-
-To receive events, you must call ipmi_set_gets_events() and set the
-"val" to non-zero. Any events that have been received by the driver
-since startup will immediately be delivered to the first user that
-registers for events. After that, if multiple users are registered
-for events, they will all receive all events that come in.
-
-For receiving commands, you have to individually register commands you
-want to receive. Call ipmi_register_for_cmd() and supply the netfn
-and command name for each command you want to receive. You also
-specify a bitmask of the channels you want to receive the command from
-(or use IPMI_CHAN_ALL for all channels if you don't care). Only one
-user may be registered for each netfn/cmd/channel, but different users
-may register for different commands, or the same command if the
-channel bitmasks do not overlap.
-
-From userland, equivalent IOCTLs are provided to do these functions.
-
-
-The Lower Layer (SMI) Interface
--------------------------------
-
-As mentioned before, multiple SMI interfaces may be registered to the
-message handler, each of these is assigned an interface number when
-they register with the message handler. They are generally assigned
-in the order they register, although if an SMI unregisters and then
-another one registers, all bets are off.
-
-The ipmi_smi.h defines the interface for management interfaces, see
-that for more details.
-
-
-The SI Driver
--------------
-
-The SI driver allows up to 4 KCS or SMIC interfaces to be configured
-in the system. By default, scan the ACPI tables for interfaces, and
-if it doesn't find any the driver will attempt to register one KCS
-interface at the spec-specified I/O port 0xca2 without interrupts.
-You can change this at module load time (for a module) with:
-
- modprobe ipmi_si.o type=<type1>,<type2>....
- ports=<port1>,<port2>... addrs=<addr1>,<addr2>...
- irqs=<irq1>,<irq2>... trydefaults=[0|1]
- regspacings=<sp1>,<sp2>,... regsizes=<size1>,<size2>,...
- regshifts=<shift1>,<shift2>,...
- slave_addrs=<addr1>,<addr2>,...
- force_kipmid=<enable1>,<enable2>,...
- kipmid_max_busy_us=<ustime1>,<ustime2>,...
- unload_when_empty=[0|1]
-
-Each of these except si_trydefaults is a list, the first item for the
-first interface, second item for the second interface, etc.
-
-The si_type may be either "kcs", "smic", or "bt". If you leave it blank, it
-defaults to "kcs".
-
-If you specify si_addrs as non-zero for an interface, the driver will
-use the memory address given as the address of the device. This
-overrides si_ports.
-
-If you specify si_ports as non-zero for an interface, the driver will
-use the I/O port given as the device address.
-
-If you specify si_irqs as non-zero for an interface, the driver will
-attempt to use the given interrupt for the device.
-
-si_trydefaults sets whether the standard IPMI interface at 0xca2 and
-any interfaces specified by ACPE are tried. By default, the driver
-tries it, set this value to zero to turn this off.
-
-The next three parameters have to do with register layout. The
-registers used by the interfaces may not appear at successive
-locations and they may not be in 8-bit registers. These parameters
-allow the layout of the data in the registers to be more precisely
-specified.
-
-The regspacings parameter give the number of bytes between successive
-register start addresses. For instance, if the regspacing is set to 4
-and the start address is 0xca2, then the address for the second
-register would be 0xca6. This defaults to 1.
-
-The regsizes parameter gives the size of a register, in bytes. The
-data used by IPMI is 8-bits wide, but it may be inside a larger
-register. This parameter allows the read and write type to specified.
-It may be 1, 2, 4, or 8. The default is 1.
-
-Since the register size may be larger than 32 bits, the IPMI data may not
-be in the lower 8 bits. The regshifts parameter give the amount to shift
-the data to get to the actual IPMI data.
-
-The slave_addrs specifies the IPMI address of the local BMC. This is
-usually 0x20 and the driver defaults to that, but in case it's not, it
-can be specified when the driver starts up.
-
-The force_ipmid parameter forcefully enables (if set to 1) or disables
-(if set to 0) the kernel IPMI daemon. Normally this is auto-detected
-by the driver, but systems with broken interrupts might need an enable,
-or users that don't want the daemon (don't need the performance, don't
-want the CPU hit) can disable it.
-
-If unload_when_empty is set to 1, the driver will be unloaded if it
-doesn't find any interfaces or all the interfaces fail to work. The
-default is one. Setting to 0 is useful with the hotmod, but is
-obviously only useful for modules.
-
-When compiled into the kernel, the parameters can be specified on the
-kernel command line as:
-
- ipmi_si.type=<type1>,<type2>...
- ipmi_si.ports=<port1>,<port2>... ipmi_si.addrs=<addr1>,<addr2>...
- ipmi_si.irqs=<irq1>,<irq2>... ipmi_si.trydefaults=[0|1]
- ipmi_si.regspacings=<sp1>,<sp2>,...
- ipmi_si.regsizes=<size1>,<size2>,...
- ipmi_si.regshifts=<shift1>,<shift2>,...
- ipmi_si.slave_addrs=<addr1>,<addr2>,...
- ipmi_si.force_kipmid=<enable1>,<enable2>,...
- ipmi_si.kipmid_max_busy_us=<ustime1>,<ustime2>,...
-
-It works the same as the module parameters of the same names.
-
-By default, the driver will attempt to detect any device specified by
-ACPI, and if none of those then a KCS device at the spec-specified
-0xca2. If you want to turn this off, set the "trydefaults" option to
-false.
-
-If your IPMI interface does not support interrupts and is a KCS or
-SMIC interface, the IPMI driver will start a kernel thread for the
-interface to help speed things up. This is a low-priority kernel
-thread that constantly polls the IPMI driver while an IPMI operation
-is in progress. The force_kipmid module parameter will all the user to
-force this thread on or off. If you force it off and don't have
-interrupts, the driver will run VERY slowly. Don't blame me,
-these interfaces suck.
-
-Unfortunately, this thread can use a lot of CPU depending on the
-interface's performance. This can waste a lot of CPU and cause
-various issues with detecting idle CPU and using extra power. To
-avoid this, the kipmid_max_busy_us sets the maximum amount of time, in
-microseconds, that kipmid will spin before sleeping for a tick. This
-value sets a balance between performance and CPU waste and needs to be
-tuned to your needs. Maybe, someday, auto-tuning will be added, but
-that's not a simple thing and even the auto-tuning would need to be
-tuned to the user's desired performance.
-
-The driver supports a hot add and remove of interfaces. This way,
-interfaces can be added or removed after the kernel is up and running.
-This is done using /sys/modules/ipmi_si/parameters/hotmod, which is a
-write-only parameter. You write a string to this interface. The string
-has the format:
- <op1>[:op2[:op3...]]
-The "op"s are:
- add|remove,kcs|bt|smic,mem|i/o,<address>[,<opt1>[,<opt2>[,...]]]
-You can specify more than one interface on the line. The "opt"s are:
- rsp=<regspacing>
- rsi=<regsize>
- rsh=<regshift>
- irq=<irq>
- ipmb=<ipmb slave addr>
-and these have the same meanings as discussed above. Note that you
-can also use this on the kernel command line for a more compact format
-for specifying an interface. Note that when removing an interface,
-only the first three parameters (si type, address type, and address)
-are used for the comparison. Any options are ignored for removing.
-
-The SMBus Driver
-----------------
-
-The SMBus driver allows up to 4 SMBus devices to be configured in the
-system. By default, the driver will register any SMBus interfaces it finds
-in the I2C address range of 0x20 to 0x4f on any adapter. You can change this
-at module load time (for a module) with:
-
- modprobe ipmi_smb.o
- addr=<adapter1>,<i2caddr1>[,<adapter2>,<i2caddr2>[,...]]
- dbg=<flags1>,<flags2>...
- [defaultprobe=1] [dbg_probe=1]
-
-The addresses are specified in pairs, the first is the adapter ID and the
-second is the I2C address on that adapter.
-
-The debug flags are bit flags for each BMC found, they are:
-IPMI messages: 1, driver state: 2, timing: 4, I2C probe: 8
-
-Setting smb_defaultprobe to zero disabled the default probing of SMBus
-interfaces at address range 0x20 to 0x4f. This means that only the
-BMCs specified on the smb_addr line will be detected.
-
-Setting smb_dbg_probe to 1 will enable debugging of the probing and
-detection process for BMCs on the SMBusses.
-
-Discovering the IPMI compliant BMC on the SMBus can cause devices
-on the I2C bus to fail. The SMBus driver writes a "Get Device ID" IPMI
-message as a block write to the I2C bus and waits for a response.
-This action can be detrimental to some I2C devices. It is highly recommended
-that the known I2c address be given to the SMBus driver in the smb_addr
-parameter. The default address range will not be used when a smb_addr
-parameter is provided.
-
-When compiled into the kernel, the addresses can be specified on the
-kernel command line as:
-
- ipmb_smb.addr=<adapter1>,<i2caddr1>[,<adapter2>,<i2caddr2>[,...]]
- ipmi_smb.dbg=<flags1>,<flags2>...
- ipmi_smb.defaultprobe=0 ipmi_smb.dbg_probe=1
-
-These are the same options as on the module command line.
-
-Note that you might need some I2C changes if CONFIG_IPMI_PANIC_EVENT
-is enabled along with this, so the I2C driver knows to run to
-completion during sending a panic event.
-
-
-Other Pieces
-------------
-
-Get the detailed info related with the IPMI device
---------------------------------------------------
-
-Some users need more detailed information about a device, like where
-the address came from or the raw base device for the IPMI interface.
-You can use the IPMI smi_watcher to catch the IPMI interfaces as they
-come or go, and to grab the information, you can use the function
-ipmi_get_smi_info(), which returns the following structure:
-
-struct ipmi_smi_info {
- enum ipmi_addr_src addr_src;
- struct device *dev;
- union {
- struct {
- void *acpi_handle;
- } acpi_info;
- } addr_info;
-};
-
-Currently special info for only for SI_ACPI address sources is
-returned. Others may be added as necessary.
-
-Note that the dev pointer is included in the above structure, and
-assuming ipmi_smi_get_info returns success, you must call put_device
-on the dev pointer.
-
-
-Watchdog
---------
-
-A watchdog timer is provided that implements the Linux-standard
-watchdog timer interface. It has three module parameters that can be
-used to control it:
-
- modprobe ipmi_watchdog timeout=<t> pretimeout=<t> action=<action type>
- preaction=<preaction type> preop=<preop type> start_now=x
- nowayout=x ifnum_to_use=n
-
-ifnum_to_use specifies which interface the watchdog timer should use.
-The default is -1, which means to pick the first one registered.
-
-The timeout is the number of seconds to the action, and the pretimeout
-is the amount of seconds before the reset that the pre-timeout panic will
-occur (if pretimeout is zero, then pretimeout will not be enabled). Note
-that the pretimeout is the time before the final timeout. So if the
-timeout is 50 seconds and the pretimeout is 10 seconds, then the pretimeout
-will occur in 40 second (10 seconds before the timeout).
-
-The action may be "reset", "power_cycle", or "power_off", and
-specifies what to do when the timer times out, and defaults to
-"reset".
-
-The preaction may be "pre_smi" for an indication through the SMI
-interface, "pre_int" for an indication through the SMI with an
-interrupts, and "pre_nmi" for a NMI on a preaction. This is how
-the driver is informed of the pretimeout.
-
-The preop may be set to "preop_none" for no operation on a pretimeout,
-"preop_panic" to set the preoperation to panic, or "preop_give_data"
-to provide data to read from the watchdog device when the pretimeout
-occurs. A "pre_nmi" setting CANNOT be used with "preop_give_data"
-because you can't do data operations from an NMI.
-
-When preop is set to "preop_give_data", one byte comes ready to read
-on the device when the pretimeout occurs. Select and fasync work on
-the device, as well.
-
-If start_now is set to 1, the watchdog timer will start running as
-soon as the driver is loaded.
-
-If nowayout is set to 1, the watchdog timer will not stop when the
-watchdog device is closed. The default value of nowayout is true
-if the CONFIG_WATCHDOG_NOWAYOUT option is enabled, or false if not.
-
-When compiled into the kernel, the kernel command line is available
-for configuring the watchdog:
-
- ipmi_watchdog.timeout=<t> ipmi_watchdog.pretimeout=<t>
- ipmi_watchdog.action=<action type>
- ipmi_watchdog.preaction=<preaction type>
- ipmi_watchdog.preop=<preop type>
- ipmi_watchdog.start_now=x
- ipmi_watchdog.nowayout=x
-
-The options are the same as the module parameter options.
-
-The watchdog will panic and start a 120 second reset timeout if it
-gets a pre-action. During a panic or a reboot, the watchdog will
-start a 120 timer if it is running to make sure the reboot occurs.
-
-Note that if you use the NMI preaction for the watchdog, you MUST NOT
-use the nmi watchdog. There is no reasonable way to tell if an NMI
-comes from the IPMI controller, so it must assume that if it gets an
-otherwise unhandled NMI, it must be from IPMI and it will panic
-immediately.
-
-Once you open the watchdog timer, you must write a 'V' character to the
-device to close it, or the timer will not stop. This is a new semantic
-for the driver, but makes it consistent with the rest of the watchdog
-drivers in Linux.
-
-
-Panic Timeouts
---------------
-
-The OpenIPMI driver supports the ability to put semi-custom and custom
-events in the system event log if a panic occurs. if you enable the
-'Generate a panic event to all BMCs on a panic' option, you will get
-one event on a panic in a standard IPMI event format. If you enable
-the 'Generate OEM events containing the panic string' option, you will
-also get a bunch of OEM events holding the panic string.
-
-
-The field settings of the events are:
-* Generator ID: 0x21 (kernel)
-* EvM Rev: 0x03 (this event is formatting in IPMI 1.0 format)
-* Sensor Type: 0x20 (OS critical stop sensor)
-* Sensor #: The first byte of the panic string (0 if no panic string)
-* Event Dir | Event Type: 0x6f (Assertion, sensor-specific event info)
-* Event Data 1: 0xa1 (Runtime stop in OEM bytes 2 and 3)
-* Event data 2: second byte of panic string
-* Event data 3: third byte of panic string
-See the IPMI spec for the details of the event layout. This event is
-always sent to the local management controller. It will handle routing
-the message to the right place
-
-Other OEM events have the following format:
-Record ID (bytes 0-1): Set by the SEL.
-Record type (byte 2): 0xf0 (OEM non-timestamped)
-byte 3: The slave address of the card saving the panic
-byte 4: A sequence number (starting at zero)
-The rest of the bytes (11 bytes) are the panic string. If the panic string
-is longer than 11 bytes, multiple messages will be sent with increasing
-sequence numbers.
-
-Because you cannot send OEM events using the standard interface, this
-function will attempt to find an SEL and add the events there. It
-will first query the capabilities of the local management controller.
-If it has an SEL, then they will be stored in the SEL of the local
-management controller. If not, and the local management controller is
-an event generator, the event receiver from the local management
-controller will be queried and the events sent to the SEL on that
-device. Otherwise, the events go nowhere since there is nowhere to
-send them.
-
-
-Poweroff
---------
-
-If the poweroff capability is selected, the IPMI driver will install
-a shutdown function into the standard poweroff function pointer. This
-is in the ipmi_poweroff module. When the system requests a powerdown,
-it will send the proper IPMI commands to do this. This is supported on
-several platforms.
-
-There is a module parameter named "poweroff_powercycle" that may
-either be zero (do a power down) or non-zero (do a power cycle, power
-the system off, then power it on in a few seconds). Setting
-ipmi_poweroff.poweroff_control=x will do the same thing on the kernel
-command line. The parameter is also available via the proc filesystem
-in /proc/sys/dev/ipmi/poweroff_powercycle. Note that if the system
-does not support power cycling, it will always do the power off.
-
-The "ifnum_to_use" parameter specifies which interface the poweroff
-code should use. The default is -1, which means to pick the first one
-registered.
-
-Note that if you have ACPI enabled, the system will prefer using ACPI to
-power off.