=====================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 athttps://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/ACPIinformation 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 has 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 going through theBMC 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 morethan one channel, it corresponds to the channel as defined in the IPMIspec. There is also an IPMB direct address for a situation where the senderis directly on an IPMB bus and doesn't have to go through the BMC.You can send messages to a specific management controller (MC) on theIPMB using the IPMI_IPMB_DIRECT_ADDR_TYPE with the following format:: struct ipmi_ipmb_direct_addr { int addr_type; short channel; unsigned char slave_addr; unsigned char rq_lun; unsigned char rs_lun; }; The channel is always zero. You can also receive commands from otherMCs that you have registered to handle and respond to them, so you canuse this to implement a management controller on a bus.. 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. This also allows you to 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, 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 to look 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, usethe 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 received 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. To respond to a received command, set the response bit in the returnednetfn, use the address from the received message, and use the samemsgid that you got in the received message. 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 be 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 allow the userto force 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/module/ipmi_si/parameters/hotmod, which is awrite-only parameter. You write a string to this interface. The stringhas the format::Lines 1–500 of 807. 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===================== The Linux IPMI Driver ===================== :Author: 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 https://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/ACPI 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 has 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. You can also enable these dynamically by setting the module parameter 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, 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_ssif - 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_powernv - A driver for access BMCs on POWERNV systems. 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. bt-bmc - This is not part of the main driver, but instead a driver for accessing a BMC-side interface of a BT interface. It is used on BMCs running 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. The IPMI 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 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 going through the BMC 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. There is also an IPMB direct address for a situation where the sender is directly on an IPMB bus and doesn't have to go through the BMC. You can send messages to a specific management controller (MC) on the IPMB using the IPMI_IPMB_DIRECT_ADDR_TYPE with the following format:: struct ipmi_ipmb_direct_addr { int addr_type; short channel; unsigned char slave_addr; unsigned char rq_lun; unsigned char rs_lun; }; The channel is always zero. You can also receive commands from other MCs that you have registered to handle and respond to them, so you can use this to implement a management controller on a bus.. 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. Watching For Interfaces ^^^^^^^^^^^^^^^^^^^^^^^ When your code comes up, the IPMI driver may or may not have detected if IPMI devices exist. So you might have to defer your setup until the device is detected, or you might be able to do it immediately. To handle this, and to allow for discovery, you register an SMI watcher with ipmi_smi_watcher_register() to iterate over interfaces and tell you when they come and go. Creating the User ^^^^^^^^^^^^^^^^^ To use 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. This also allows you to 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_settime() 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 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, use 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 received 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. To respond to a received command, set the response bit in the returned netfn, use the address from the received message, and use the same msgid that you got in the received message. 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 KCS, BT, and SMIC interfaces to be configured in the system. It discovers interfaces through a host of different methods, depending on the system. You can specify up to four interfaces on the module load line and control 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 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 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 ports as non-zero for an interface, the driver will use the I/O port given as the device address. If you specify irqs as non-zero for an interface, the driver will attempt to use the given interrupt for the device. The other try... items disable discovery by their corresponding names. These are all enabled by default, set them to zero to disable them. The tryplatform disables openfirmware. 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 be 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.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 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 allow 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/module/ipmi_si/parameters/hotmod, which is a write-only parameter. You write a string to this interface. The string has the format::