The Linux IPMI Driver¶
| Author: | Corey Minyard <minyard@mvista.com> / <minyard@acm.org> |
|---|
The Intelligent Platform Management Interface, or IPMI, is astandard for controlling intelligent devices that monitor a system.It provides for dynamic discovery of sensors in the system and theability to monitor the sensors and be informed when the sensor’svalues change or go outside certain boundaries. It also has astandardized database for field-replaceable units (FRUs) and a watchdogtimer.
To use this, you need an interface to an IPMI controller in yoursystem (called a Baseboard Management Controller, or BMC) andmanagement software that can use the IPMI system.
This document describes how to use the IPMI driver for Linux. If youare not familiar with IPMI itself, see the web site athttp://www.intel.com/design/servers/ipmi/index.htm. IPMI is a bigsubject and I can’t cover it all here!
Configuration¶
The Linux IPMI driver is modular, which means you have to pick severalthings to have it work right depending on your hardware. Most ofthese are available in the ‘Character Devices’ menu then the IPMImenu.
No matter what, you must pick ‘IPMI top-level message handler’ to useIPMI. 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 accessfrom userland, you need to select ‘Device interface for IPMI’ if youwant access through a device driver.
The driver interface depends on your hardware. If your systemproperly provides the SMBIOS info for IPMI, the driver will detect itand just work. If you have a board with a standard interface (Thesewill generally be either “KCS”, “SMIC”, or “BT”, consult your hardwaremanual), choose the ‘IPMI SI handler’ option. A driver also existsfor direct I2C access to the IPMI management controller. Some boardssupport this, but it is unknown if it will work on every board. Forthis, choose ‘IPMI SMBus handler’, but be ready to try to do somefiguring to see if it will work on your system if the SMBIOS/APCIinformation is wrong or not present. It is fairly safe to have boththese enabled and let the drivers auto-detect what is present.
You should generally enable ACPI on your system, as systems with IPMIcan have ACPI tables describing them.
If you have a standard interface and the board manufacturer has donetheir job correctly, the IPMI controller should be automaticallydetected (via ACPI or SMBIOS tables) and should just work. Sadly,many boards do not have this information. The driver attemptsstandard defaults, but they may not work. If you fall into thissituation, 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 intothe kernel, then via a kernel command-line option you can have thewatchdog timer start as soon as it initializes. It also have a lotof other options, see the ‘Watchdog’ section below for more details.Note that you can also have the watchdog continue to run if it isclosed (by default it is disabled on close). Go into the ‘WatchdogCards’ 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 systemcan be powered off by IPMI. It is safe to enable this even if yoursystem doesn’t support this option. This works on ATCA systems, theRadisys CPI1 card, and any IPMI system that supports standard chassismanagement 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. Ifyou want the whole panic string put into the event log using OEMevents, enable the ‘Generate OEM events containing the panic string’option. You can also enable these dynamically by setting the moduleparameter named “panic_op” in the ipmi_msghandler module to “event”or “string”. Setting that parameter to “none” disables this function.
Basic Design¶
The Linux IPMI driver is designed to be very modular and flexible, youonly need to take the pieces you need and you can use it in manydifferent ways. Because of that, it’s broken into many chunks ofcode. These chunks (by module name) are:
ipmi_msghandler - This is the central piece of software for the IPMIsystem. It handles all messages, message timing, and responses. TheIPMI users tie into this, and the IPMI physical interfaces (calledSystem Management Interfaces, or SMIs) also tie in here. Thisprovides the kernelland interface for IPMI, but does not provide aninterface for use by application processes.
ipmi_devintf - This provides a userland IOCTL interface for the IPMIdriver, each open file for this device ties in to the message handleras 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 yourown custom interface, you probably need to use this.
ipmi_ssif - A driver for accessing BMCs on the SMBus. It uses theI2C kernel driver’s SMBus interfaces to send and receive IPMI messagesover the SMBus.
ipmi_powernv - A driver for access BMCs on POWERNV systems.
ipmi_watchdog - IPMI requires systems to have a very capable watchdogtimer. This driver implements the standard Linux watchdog timerinterface on top of the IPMI message handler.
ipmi_poweroff - Some systems support the ability to be turned off viaIPMI commands.
bt-bmc - This is not part of the main driver, but instead a driver foraccessing a BMC-side interface of a BT interface. It is used on BMCsrunning Linux to provide an interface to the host.
These are all individually selectable via configuration options.
Much documentation for the interface is in the include files. TheIPMI include files are:
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 overlayto 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 drivercurrently 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 talkingstraight to the BMC on the current card. The channel must beIPMI_BMC_CHANNEL.
Messages that are destined to go out on the IPMB bus use theIPMI_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 morethan one channel, it corresponds to the channel as defined in the IPMIspec.
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. Thedata portion is just the data to be send (do NOT put addressing infohere) or the response. Note that the completion code of a response isthe first item in “data”, it is not stripped out because that is howall the messages are defined in the spec (and thus makes counting theoffsets a little easier :-).
When using the IOCTL interface from userland, you must provide a blockof data for “data”, fill it, and set data_len to the length of theblock of data, even when receiving messages. Otherwise the driverwill have no place to put the message.
Messages coming up from the message handler in kernelland will come inas:
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 messageappropriately.
The Upper Layer Interface (Message Handler)¶
The upper layer of the interface provides the users with a consistentview of the IPMI interfaces. It allows multiple SMI interfaces to beaddressed (because some boards actually have multiple BMCs on them)and the user should not have to care what type of SMI is below them.
Watching For Interfaces¶
When your code comes up, the IPMI driver may or may not have detectedif IPMI devices exist. So you might have to defer your setup untilthe device is detected, or you might be able to do it immediately.To handle this, and to allow for discovery, you register an SMIwatcher with ipmi_smi_watcher_register() to iterate over interfacesand tell you when they come and go.
Creating the User¶
To use the message handler, you must first create a user usingipmi_create_user. The interface number specifies which SMI you wantto connect to, and you must supply callback functions to be calledwhen data comes in. The callback function can run at interrupt level,so be careful using the callbacks. This also allows to you pass in apiece of data, the handler_data, that will be passed back to you onall calls.
Once you are done, call ipmi_destroy_user() to get rid of the user.
From userland, opening the device automatically creates a user, andclosing the device automatically destroys the user.
Messaging¶
To send a message from kernel-land, the ipmi_request_settime() call doespretty much all message handling. Most of the parameter areself-explanatory. However, it takes a “msgid” parameter. This is NOTthe sequence number of messages. It is simply a long value that ispassed back when the response for the message is returned. You mayuse it for anything you like.
Responses come back in the function pointed to by the ipmi_recv_hndlfield of the “handler” that you passed in to ipmi_create_user().Remember again, these may be running at interrupt level. Remember tolook at the receive type, too.
From userland, you fill out an ipmi_req_t structure and use theIPMICTL_SEND_COMMAND ioctl. For incoming stuff, you can use select()or poll() to wait for messages to come in. However, you cannot useread() to get them, you must call the IPMICTL_RECEIVE_MSG with theipmi_recv_t structure to actually get the message. Remember that youmust supply a pointer to a block of data in the msg.data field, andyou 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 anEMSGSIZE error and the driver will leave the data in the receivequeue. If you want to get it and have it truncate the message, usthe IPMICTL_RECEIVE_MSG_TRUNC ioctl.
When you send a command (which is defined by the lowest-order bit ofthe netfn per the IPMI spec) on the IPMB bus, the driver willautomatically assign the sequence number to the command and save thecommand. If the response is not receive in the IPMI-specified 5seconds, it will generate a response automatically saying the commandtimed out. If an unsolicited response comes in (if it was after 5seconds, for instance), that response will be ignored.
In kernelland, after you receive a message and are done with it, youMUST call ipmi_free_recv_msg() on it, or you will leak messages. Notethat you should NEVER mess with the “done” field of a message, that isrequired to properly clean up the message.
Note that when sending, there is an ipmi_request_supply_msgs() callthat lets you supply the smi and receive message. This is useful forpieces of code that need to work even if the system is out of buffers(the watchdog timer uses this, for instance). You supply your ownbuffer 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 receivingcommands (commands are messages that are not responses, they arecommands that other things on the IPMB bus have sent you). To receivethese, you must register for them, they will not automatically be sentto 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 driversince startup will immediately be delivered to the first user thatregisters for events. After that, if multiple users are registeredfor events, they will all receive all events that come in.
For receiving commands, you have to individually register commands youwant to receive. Call ipmi_register_for_cmd() and supply the netfnand command name for each command you want to receive. You alsospecify 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 oneuser may be registered for each netfn/cmd/channel, but different usersmay register for different commands, or the same command if thechannel 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 themessage handler, each of these is assigned an interface number whenthey register with the message handler. They are generally assignedin the order they register, although if an SMI unregisters and thenanother one registers, all bets are off.
The ipmi_smi.h defines the interface for management interfaces, seethat for more details.
The SI Driver¶
The SI driver allows KCS, BT, and SMIC interfaces to be configuredin the system. It discovers interfaces through a host of differentmethods, depending on the system.
You can specify up to four interfaces on the module load line andcontrol some module parameters:
modprobe ipmi_si.o type=<type1>,<type2>.... ports=<port1>,<port2>... addrs=<addr1>,<addr2>... irqs=<irq1>,<irq2>... 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] trydmi=[0|1] tryacpi=[0|1] tryplatform=[0|1] trypci=[0|1]
Each of these except try… items is a list, the first item for thefirst interface, second item for the second interface, etc.
The si_type may be either “kcs”, “smic”, or “bt”. If you leave it blank, itdefaults to “kcs”.
If you specify addrs as non-zero for an interface, the driver willuse the memory address given as the address of the device. Thisoverrides si_ports.
If you specify ports as non-zero for an interface, the driver willuse the I/O port given as the device address.
If you specify irqs as non-zero for an interface, the driver willattempt to use the given interrupt for the device.
The other try… items disable discovery by their correspondingnames. These are all enabled by default, set them to zero to disablethem. The tryplatform disables openfirmware.
The next three parameters have to do with register layout. Theregisters used by the interfaces may not appear at successivelocations and they may not be in 8-bit registers. These parametersallow the layout of the data in the registers to be more preciselyspecified.
The regspacings parameter give the number of bytes between successiveregister start addresses. For instance, if the regspacing is set to 4and the start address is 0xca2, then the address for the secondregister would be 0xca6. This defaults to 1.
The regsizes parameter gives the size of a register, in bytes. Thedata used by IPMI is 8-bits wide, but it may be inside a largerregister. 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 notbe in the lower 8 bits. The regshifts parameter give the amount to shiftthe data to get to the actual IPMI data.
The slave_addrs specifies the IPMI address of the local BMC. This isusually 0x20 and the driver defaults to that, but in case it’s not, itcan 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-detectedby 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’twant the CPU hit) can disable it.
If unload_when_empty is set to 1, the driver will be unloaded if itdoesn’t find any interfaces or all the interfaces fail to work. Thedefault is one. Setting to 0 is useful with the hotmod, but isobviously only useful for modules.
When compiled into the kernel, the parameters can be specified on thekernel 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.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.
If your IPMI interface does not support interrupts and is a KCS orSMIC interface, the IPMI driver will start a kernel thread for theinterface to help speed things up. This is a low-priority kernelthread that constantly polls the IPMI driver while an IPMI operationis in progress. The force_kipmid module parameter will all the user toforce this thread on or off. If you force it off and don’t haveinterrupts, the driver will run VERY slowly. Don’t blame me,these interfaces suck.
Unfortunately, this thread can use a lot of CPU depending on theinterface’s performance. This can waste a lot of CPU and causevarious issues with detecting idle CPU and using extra power. Toavoid this, the kipmid_max_busy_us sets the maximum amount of time, inmicroseconds, that kipmid will spin before sleeping for a tick. Thisvalue sets a balance between performance and CPU waste and needs to betuned to your needs. Maybe, someday, auto-tuning will be added, butthat’s not a simple thing and even the auto-tuning would need to betuned 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 awrite-only parameter. You write a string to this interface. The stringhas 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 youcan also use this on the kernel command line for a more compact formatfor 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 (SSIF)¶
The SMBus driver allows up to 4 SMBus devices to be configured in thesystem. By default, the driver will only register with something itfinds in DMI or ACPI tables. You can change thisat module load time (for a module) with:
modprobe ipmi_ssif.o addr=<i2caddr1>[,<i2caddr2>[,...]] adapter=<adapter1>[,<adapter2>[...]] dbg=<flags1>,<flags2>... slave_addrs=<addr1>,<addr2>,... tryacpi=[0|1] trydmi=[0|1] [dbg_probe=1]
The addresses are normal I2C addresses. The adapter is the stringname of the adapter, as shown in /sys/class/i2c-adapter/i2c-<n>/name.It isNOT i2c-<n> itself. Also, the comparison is done ignoringspaces, so if the name is “This is an I2C chip” you can sayadapter_name=ThisisanI2cchip. This is because it’s hard to pass inspaces in kernel parameters.
The debug flags are bit flags for each BMC found, they are:IPMI messages: 1, driver state: 2, timing: 4, I2C probe: 8
The tryxxx parameters can be used to disable detecting interfacesfrom various sources.
Setting dbg_probe to 1 will enable debugging of the probing anddetection process for BMCs on the SMBusses.
The slave_addrs specifies the IPMI address of the local BMC. This isusually 0x20 and the driver defaults to that, but in case it’s not, itcan be specified when the driver starts up.
Discovering the IPMI compliant BMC on the SMBus can cause devices onthe I2C bus to fail. The SMBus driver writes a “Get Device ID” IPMImessage as a block write to the I2C bus and waits for a response.This action can be detrimental to some I2C devices. It is highlyrecommended that the known I2C address be given to the SMBus driver inthe smb_addr parameter unless you have DMI or ACPI data to tell thedriver what to use.
When compiled into the kernel, the addresses can be specified on thekernel command line as:
ipmb_ssif.addr=<i2caddr1>[,<i2caddr2>[...]] ipmi_ssif.adapter=<adapter1>[,<adapter2>[...]] ipmi_ssif.dbg=<flags1>[,<flags2>[...]] ipmi_ssif.dbg_probe=1 ipmi_ssif.slave_addrs=<addr1>[,<addr2>[...]] ipmi_ssif.tryacpi=[0|1] ipmi_ssif.trydmi=[0|1]
These are the same options as on the module command line.
The I2C driver does not support non-blocking access or polling, sothis driver cannod to IPMI panic events, extend the watchdog at panictime, or other panic-related IPMI functions without special kernelpatches and driver modifications. You can get those at the openipmiweb page.
The driver supports a hot add and remove of interfaces through the I2Csysfs interface.
Other Pieces¶
Get the detailed info related with the IPMI device¶
Some users need more detailed information about a device, like wherethe 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 theycome or go, and to grab the information, you can use the functionipmi_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 isreturned. Others may be added as necessary.
Note that the dev pointer is included in the above structure, andassuming ipmi_smi_get_info returns success, you must call put_deviceon the dev pointer.
Watchdog¶
A watchdog timer is provided that implements the Linux-standardwatchdog timer interface. It has three module parameters that can beused 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 panic_wdt_timeout=<t>
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 pretimeoutis the amount of seconds before the reset that the pre-timeout panic willoccur (if pretimeout is zero, then pretimeout will not be enabled). Notethat the pretimeout is the time before the final timeout. So if thetimeout is 50 seconds and the pretimeout is 10 seconds, then the pretimeoutwill occur in 40 second (10 seconds before the timeout). The panic_wdt_timeoutis the value of timeout which is set on kernel panic, in order to let actionssuch as kdump to occur during panic.
The action may be “reset”, “power_cycle”, or “power_off”, andspecifies what to do when the timer times out, and defaults to“reset”.
The preaction may be “pre_smi” for an indication through the SMIinterface, “pre_int” for an indication through the SMI with aninterrupts, and “pre_nmi” for a NMI on a preaction. This is howthe 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 pretimeoutoccurs. 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 readon the device when the pretimeout occurs. Select and fasync work onthe device, as well.
If start_now is set to 1, the watchdog timer will start running assoon as the driver is loaded.
If nowayout is set to 1, the watchdog timer will not stop when thewatchdog device is closed. The default value of nowayout is trueif the CONFIG_WATCHDOG_NOWAYOUT option is enabled, or false if not.
When compiled into the kernel, the kernel command line is availablefor 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 ipmi_watchdog.panic_wdt_timeout=<t>
The options are the same as the module parameter options.
The watchdog will panic and start a 120 second reset timeout if itgets a pre-action. During a panic or a reboot, the watchdog willstart 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 NOTuse the nmi watchdog. There is no reasonable way to tell if an NMIcomes from the IPMI controller, so it must assume that if it gets anotherwise unhandled NMI, it must be from IPMI and it will panicimmediately.
Once you open the watchdog timer, you must write a ‘V’ character to thedevice to close it, or the timer will not stop. This is a new semanticfor the driver, but makes it consistent with the rest of the watchdogdrivers in Linux.
Panic Timeouts¶
The OpenIPMI driver supports the ability to put semi-custom and customevents 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 getone event on a panic in a standard IPMI event format. If you enablethe ‘Generate OEM events containing the panic string’ option, you willalso 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 isalways sent to the local management controller. It will handle routingthe 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 stringis longer than 11 bytes, multiple messages will be sent with increasingsequence numbers.
Because you cannot send OEM events using the standard interface, thisfunction will attempt to find an SEL and add the events there. Itwill first query the capabilities of the local management controller.If it has an SEL, then they will be stored in the SEL of the localmanagement controller. If not, and the local management controller isan event generator, the event receiver from the local managementcontroller will be queried and the events sent to the SEL on thatdevice. Otherwise, the events go nowhere since there is nowhere tosend them.
Poweroff¶
If the poweroff capability is selected, the IPMI driver will installa shutdown function into the standard poweroff function pointer. Thisis in the ipmi_poweroff module. When the system requests a powerdown,it will send the proper IPMI commands to do this. This is supported onseveral platforms.
There is a module parameter named “poweroff_powercycle” that mayeither be zero (do a power down) or non-zero (do a power cycle, powerthe system off, then power it on in a few seconds). Settingipmi_poweroff.poweroff_control=x will do the same thing on the kernelcommand line. The parameter is also available via the proc filesystemin /proc/sys/dev/ipmi/poweroff_powercycle. Note that if the systemdoes not support power cycling, it will always do the power off.
The “ifnum_to_use” parameter specifies which interface the poweroffcode should use. The default is -1, which means to pick the first oneregistered.
Note that if you have ACPI enabled, the system will prefer using ACPI topower off.