Documentation/IPMI.txt

   1
   2                           The Linux IPMI Driver
   3                           ---------------------
   4                               Corey Minyard
   5                           <minyard@mvista.com>
   6                             <minyard@acm.org>
   7
   8 The Intelligent Platform Management Interface, or IPMI, is a
   9 standard for controlling intelligent devices that monitor a system.
  10 It provides for dynamic discovery of sensors in the system and the
  11 ability to monitor the sensors and be informed when the sensor's
  12 values change or go outside certain boundaries.  It also has a
  13 standardized database for field-replaceable units (FRUs) and a watchdog
  14 timer.
  15
  16 To use this, you need an interface to an IPMI controller in your
  17 system (called a Baseboard Management Controller, or BMC) and
  18 management software that can use the IPMI system.
  19
  20 This document describes how to use the IPMI driver for Linux.  If you
  21 are not familiar with IPMI itself, see the web site at
  22 http://www.intel.com/design/servers/ipmi/index.htm.  IPMI is a big
  23 subject and I can't cover it all here!
  24
  25 Configuration
  26 -------------
  27
  28 The Linux IPMI driver is modular, which means you have to pick several
  29 things to have it work right depending on your hardware.  Most of
  30 these are available in the 'Character Devices' menu then the IPMI
  31 menu.
  32
  33 No matter what, you must pick 'IPMI top-level message handler' to use
  34 IPMI.  What you do beyond that depends on your needs and hardware.
  35
  36 The message handler does not provide any user-level interfaces.
  37 Kernel code (like the watchdog) can still use it.  If you need access
  38 from userland, you need to select 'Device interface for IPMI' if you
  39 want access through a device driver.
  40
  41 The driver interface depends on your hardware.  If your system
  42 properly provides the SMBIOS info for IPMI, the driver will detect it
  43 and just work.  If you have a board with a standard interface (These
  44 will generally be either "KCS", "SMIC", or "BT", consult your hardware
  45 manual), choose the 'IPMI SI handler' option.  A driver also exists
  46 for direct I2C access to the IPMI management controller.  Some boards
  47 support this, but it is unknown if it will work on every board.  For
  48 this, choose 'IPMI SMBus handler', but be ready to try to do some
  49 figuring to see if it will work on your system if the SMBIOS/APCI
  50 information is wrong or not present.  It is fairly safe to have both
  51 these enabled and let the drivers auto-detect what is present.
  52
  53 You should generally enable ACPI on your system, as systems with IPMI
  54 can have ACPI tables describing them.
  55
  56 If you have a standard interface and the board manufacturer has done
  57 their job correctly, the IPMI controller should be automatically
  58 detected (via ACPI or SMBIOS tables) and should just work.  Sadly,
  59 many boards do not have this information.  The driver attempts
  60 standard defaults, but they may not work.  If you fall into this
  61 situation, you need to read the section below named 'The SI Driver' or
  62 "The SMBus Driver" on how to hand-configure your system.
  63
  64 IPMI defines a standard watchdog timer.  You can enable this with the
  65 'IPMI Watchdog Timer' config option.  If you compile the driver into
  66 the kernel, then via a kernel command-line option you can have the
  67 watchdog timer start as soon as it initializes.  It also have a lot
  68 of other options, see the 'Watchdog' section below for more details.
  69 Note that you can also have the watchdog continue to run if it is
  70 closed (by default it is disabled on close).  Go into the 'Watchdog
  71 Cards' menu, enable 'Watchdog Timer Support', and enable the option
  72 'Disable watchdog shutdown on close'.
  73
  74 IPMI systems can often be powered off using IPMI commands.  Select
  75 'IPMI Poweroff' to do this.  The driver will auto-detect if the system
  76 can be powered off by IPMI.  It is safe to enable this even if your
  77 system doesn't support this option.  This works on ATCA systems, the
  78 Radisys CPI1 card, and any IPMI system that supports standard chassis
  79 management commands.
  80
  81 If you want the driver to put an event into the event log on a panic,
  82 enable the 'Generate a panic event to all BMCs on a panic' option.  If
  83 you want the whole panic string put into the event log using OEM
  84 events, enable the 'Generate OEM events containing the panic string'
  85 option.
  86
  87 Basic Design
  88 ------------
  89
  90 The Linux IPMI driver is designed to be very modular and flexible, you
  91 only need to take the pieces you need and you can use it in many
  92 different ways.  Because of that, it's broken into many chunks of
  93 code.  These chunks (by module name) are:
  94
  95 ipmi_msghandler - This is the central piece of software for the IPMI
  96 system.  It handles all messages, message timing, and responses.  The
  97 IPMI users tie into this, and the IPMI physical interfaces (called
  98 System Management Interfaces, or SMIs) also tie in here.  This
  99 provides the kernelland interface for IPMI, but does not provide an
 100 interface for use by application processes.
 101
 102 ipmi_devintf - This provides a userland IOCTL interface for the IPMI
 103 driver, each open file for this device ties in to the message handler
 104 as an IPMI user.
 105
 106 ipmi_si - A driver for various system interfaces.  This supports KCS,
 107 SMIC, and BT interfaces.  Unless you have an SMBus interface or your
 108 own custom interface, you probably need to use this.
 109
 110 ipmi_ssif - A driver for accessing BMCs on the SMBus. It uses the
 111 I2C kernel driver's SMBus interfaces to send and receive IPMI messages
 112 over the SMBus.
 113
 114 ipmi_watchdog - IPMI requires systems to have a very capable watchdog
 115 timer.  This driver implements the standard Linux watchdog timer
 116 interface on top of the IPMI message handler.
 117
 118 ipmi_poweroff - Some systems support the ability to be turned off via
 119 IPMI commands.
 120
 121 These are all individually selectable via configuration options.
 122
 123 Note that the KCS-only interface has been removed.  The af_ipmi driver
 124 is no longer supported and has been removed because it was impossible
 125 to do 32 bit emulation on 64-bit kernels with it.
 126
 127 Much documentation for the interface is in the include files.  The
 128 IPMI include files are:
 129
 130 net/af_ipmi.h - Contains the socket interface.
 131
 132 linux/ipmi.h - Contains the user interface and IOCTL interface for IPMI.
 133
 134 linux/ipmi_smi.h - Contains the interface for system management interfaces
 135 (things that interface to IPMI controllers) to use.
 136
 137 linux/ipmi_msgdefs.h - General definitions for base IPMI messaging.
 138
 139
 140 Addressing
 141 ----------
 142
 143 The IPMI addressing works much like IP addresses, you have an overlay
 144 to handle the different address types.  The overlay is:
 145
 146   struct ipmi_addr
 147   {
 148         int   addr_type;
 149         short channel;
 150         char  data[IPMI_MAX_ADDR_SIZE];
 151   };
 152
 153 The addr_type determines what the address really is.  The driver
 154 currently understands two different types of addresses.
 155
 156 "System Interface" addresses are defined as:
 157
 158   struct ipmi_system_interface_addr
 159   {
 160         int   addr_type;
 161         short channel;
 162   };
 163
 164 and the type is IPMI_SYSTEM_INTERFACE_ADDR_TYPE.  This is used for talking
 165 straight to the BMC on the current card.  The channel must be
 166 IPMI_BMC_CHANNEL.
 167
 168 Messages that are destined to go out on the IPMB bus use the
 169 IPMI_IPMB_ADDR_TYPE address type.  The format is
 170
 171   struct ipmi_ipmb_addr
 172   {
 173         int           addr_type;
 174         short         channel;
 175         unsigned char slave_addr;
 176         unsigned char lun;
 177   };
 178
 179 The "channel" here is generally zero, but some devices support more
 180 than one channel, it corresponds to the channel as defined in the IPMI
 181 spec.
 182
 183
 184 Messages
 185 --------
 186
 187 Messages are defined as:
 188
 189 struct ipmi_msg
 190 {
 191         unsigned char netfn;
 192         unsigned char lun;
 193         unsigned char cmd;
 194         unsigned char *data;
 195         int           data_len;
 196 };
 197
 198 The driver takes care of adding/stripping the header information.  The
 199 data portion is just the data to be send (do NOT put addressing info
 200 here) or the response.  Note that the completion code of a response is
 201 the first item in "data", it is not stripped out because that is how
 202 all the messages are defined in the spec (and thus makes counting the
 203 offsets a little easier :-).
 204
 205 When using the IOCTL interface from userland, you must provide a block
 206 of data for "data", fill it, and set data_len to the length of the
 207 block of data, even when receiving messages.  Otherwise the driver
 208 will have no place to put the message.
 209
 210 Messages coming up from the message handler in kernelland will come in
 211 as:
 212
 213   struct ipmi_recv_msg
 214   {
 215         struct list_head link;
 216
 217         /* The type of message as defined in the "Receive Types"
 218            defines above. */
 219         int         recv_type;
 220
 221         ipmi_user_t      *user;
 222         struct ipmi_addr addr;
 223         long             msgid;
 224         struct ipmi_msg  msg;
 225
 226         /* Call this when done with the message.  It will presumably free
 227            the message and do any other necessary cleanup. */
 228         void (*done)(struct ipmi_recv_msg *msg);
 229
 230         /* Place-holder for the data, don't make any assumptions about
 231            the size or existence of this, since it may change. */
 232         unsigned char   msg_data[IPMI_MAX_MSG_LENGTH];
 233   };
 234
 235 You should look at the receive type and handle the message
 236 appropriately.
 237
 238
 239 The Upper Layer Interface (Message Handler)
 240 -------------------------------------------
 241
 242 The upper layer of the interface provides the users with a consistent
 243 view of the IPMI interfaces.  It allows multiple SMI interfaces to be
 244 addressed (because some boards actually have multiple BMCs on them)
 245 and the user should not have to care what type of SMI is below them.
 246
 247
 248 Creating the User
 249
 250 To user the message handler, you must first create a user using
 251 ipmi_create_user.  The interface number specifies which SMI you want
 252 to connect to, and you must supply callback functions to be called
 253 when data comes in.  The callback function can run at interrupt level,
 254 so be careful using the callbacks.  This also allows to you pass in a
 255 piece of data, the handler_data, that will be passed back to you on
 256 all calls.
 257
 258 Once you are done, call ipmi_destroy_user() to get rid of the user.
 259
 260 From userland, opening the device automatically creates a user, and
 261 closing the device automatically destroys the user.
 262
 263
 264 Messaging
 265
 266 To send a message from kernel-land, the ipmi_request() call does
 267 pretty much all message handling.  Most of the parameter are
 268 self-explanatory.  However, it takes a "msgid" parameter.  This is NOT
 269 the sequence number of messages.  It is simply a long value that is
 270 passed back when the response for the message is returned.  You may
 271 use it for anything you like.
 272
 273 Responses come back in the function pointed to by the ipmi_recv_hndl
 274 field of the "handler" that you passed in to ipmi_create_user().
 275 Remember again, these may be running at interrupt level.  Remember to
 276 look at the receive type, too.
 277
 278 From userland, you fill out an ipmi_req_t structure and use the
 279 IPMICTL_SEND_COMMAND ioctl.  For incoming stuff, you can use select()
 280 or poll() to wait for messages to come in.  However, you cannot use
 281 read() to get them, you must call the IPMICTL_RECEIVE_MSG with the
 282 ipmi_recv_t structure to actually get the message.  Remember that you
 283 must supply a pointer to a block of data in the msg.data field, and
 284 you must fill in the msg.data_len field with the size of the data.
 285 This gives the receiver a place to actually put the message.
 286
 287 If the message cannot fit into the data you provide, you will get an
 288 EMSGSIZE error and the driver will leave the data in the receive
 289 queue.  If you want to get it and have it truncate the message, us
 290 the IPMICTL_RECEIVE_MSG_TRUNC ioctl.
 291
 292 When you send a command (which is defined by the lowest-order bit of
 293 the netfn per the IPMI spec) on the IPMB bus, the driver will
 294 automatically assign the sequence number to the command and save the
 295 command.  If the response is not receive in the IPMI-specified 5
 296 seconds, it will generate a response automatically saying the command
 297 timed out.  If an unsolicited response comes in (if it was after 5
 298 seconds, for instance), that response will be ignored.
 299
 300 In kernelland, after you receive a message and are done with it, you
 301 MUST call ipmi_free_recv_msg() on it, or you will leak messages.  Note
 302 that you should NEVER mess with the "done" field of a message, that is
 303 required to properly clean up the message.
 304
 305 Note that when sending, there is an ipmi_request_supply_msgs() call
 306 that lets you supply the smi and receive message.  This is useful for
 307 pieces of code that need to work even if the system is out of buffers
 308 (the watchdog timer uses this, for instance).  You supply your own
 309 buffer and own free routines.  This is not recommended for normal use,
 310 though, since it is tricky to manage your own buffers.
 311
 312
 313 Events and Incoming Commands
 314
 315 The driver takes care of polling for IPMI events and receiving
 316 commands (commands are messages that are not responses, they are
 317 commands that other things on the IPMB bus have sent you).  To receive
 318 these, you must register for them, they will not automatically be sent
 319 to you.
 320
 321 To receive events, you must call ipmi_set_gets_events() and set the
 322 "val" to non-zero.  Any events that have been received by the driver
 323 since startup will immediately be delivered to the first user that
 324 registers for events.  After that, if multiple users are registered
 325 for events, they will all receive all events that come in.
 326
 327 For receiving commands, you have to individually register commands you
 328 want to receive.  Call ipmi_register_for_cmd() and supply the netfn
 329 and command name for each command you want to receive.  You also
 330 specify a bitmask of the channels you want to receive the command from
 331 (or use IPMI_CHAN_ALL for all channels if you don't care).  Only one
 332 user may be registered for each netfn/cmd/channel, but different users
 333 may register for different commands, or the same command if the
 334 channel bitmasks do not overlap.
 335
 336 From userland, equivalent IOCTLs are provided to do these functions.
 337
 338
 339 The Lower Layer (SMI) Interface
 340 -------------------------------
 341
 342 As mentioned before, multiple SMI interfaces may be registered to the
 343 message handler, each of these is assigned an interface number when
 344 they register with the message handler.  They are generally assigned
 345 in the order they register, although if an SMI unregisters and then
 346 another one registers, all bets are off.
 347
 348 The ipmi_smi.h defines the interface for management interfaces, see
 349 that for more details.
 350
 351
 352 The SI Driver
 353 -------------
 354
 355 The SI driver allows up to 4 KCS or SMIC interfaces to be configured
 356 in the system.  By default, scan the ACPI tables for interfaces, and
 357 if it doesn't find any the driver will attempt to register one KCS
 358 interface at the spec-specified I/O port 0xca2 without interrupts.
 359 You can change this at module load time (for a module) with:
 360
 361   modprobe ipmi_si.o type=<type1>,<type2>....
 362        ports=<port1>,<port2>... addrs=<addr1>,<addr2>...
 363        irqs=<irq1>,<irq2>...
 364        regspacings=<sp1>,<sp2>,... regsizes=<size1>,<size2>,...
 365        regshifts=<shift1>,<shift2>,...
 366        slave_addrs=<addr1>,<addr2>,...
 367        force_kipmid=<enable1>,<enable2>,...
 368        kipmid_max_busy_us=<ustime1>,<ustime2>,...
 369        unload_when_empty=[0|1]
 370        trydefaults=[0|1] trydmi=[0|1] tryacpi=[0|1]
 371        tryplatform=[0|1] trypci=[0|1]
 372
 373 Each of these except try... items is a list, the first item for the
 374 first interface, second item for the second interface, etc.
 375
 376 The si_type may be either "kcs", "smic", or "bt".  If you leave it blank, it
 377 defaults to "kcs".
 378
 379 If you specify addrs as non-zero for an interface, the driver will
 380 use the memory address given as the address of the device.  This
 381 overrides si_ports.
 382
 383 If you specify ports as non-zero for an interface, the driver will
 384 use the I/O port given as the device address.
 385
 386 If you specify irqs as non-zero for an interface, the driver will
 387 attempt to use the given interrupt for the device.
 388
 389 trydefaults sets whether the standard IPMI interface at 0xca2 and
 390 any interfaces specified by ACPE are tried.  By default, the driver
 391 tries it, set this value to zero to turn this off.
 392
 393 The other try... items disable discovery by their corresponding
 394 names.  These are all enabled by default, set them to zero to disable
 395 them.  The tryplatform disables openfirmware.
 396
 397 The next three parameters have to do with register layout.  The
 398 registers used by the interfaces may not appear at successive
 399 locations and they may not be in 8-bit registers.  These parameters
 400 allow the layout of the data in the registers to be more precisely
 401 specified.
 402
 403 The regspacings parameter give the number of bytes between successive
 404 register start addresses.  For instance, if the regspacing is set to 4
 405 and the start address is 0xca2, then the address for the second
 406 register would be 0xca6.  This defaults to 1.
 407
 408 The regsizes parameter gives the size of a register, in bytes.  The
 409 data used by IPMI is 8-bits wide, but it may be inside a larger
 410 register.  This parameter allows the read and write type to specified.
 411 It may be 1, 2, 4, or 8.  The default is 1.
 412
 413 Since the register size may be larger than 32 bits, the IPMI data may not
 414 be in the lower 8 bits.  The regshifts parameter give the amount to shift
 415 the data to get to the actual IPMI data.
 416
 417 The slave_addrs specifies the IPMI address of the local BMC.  This is
 418 usually 0x20 and the driver defaults to that, but in case it's not, it
 419 can be specified when the driver starts up.
 420
 421 The force_ipmid parameter forcefully enables (if set to 1) or disables
 422 (if set to 0) the kernel IPMI daemon.  Normally this is auto-detected
 423 by the driver, but systems with broken interrupts might need an enable,
 424 or users that don't want the daemon (don't need the performance, don't
 425 want the CPU hit) can disable it.
 426
 427 If unload_when_empty is set to 1, the driver will be unloaded if it
 428 doesn't find any interfaces or all the interfaces fail to work.  The
 429 default is one.  Setting to 0 is useful with the hotmod, but is
 430 obviously only useful for modules.
 431
 432 When compiled into the kernel, the parameters can be specified on the
 433 kernel command line as:
 434
 435   ipmi_si.type=<type1>,<type2>...
 436        ipmi_si.ports=<port1>,<port2>... ipmi_si.addrs=<addr1>,<addr2>...
 437        ipmi_si.irqs=<irq1>,<irq2>... ipmi_si.trydefaults=[0|1]
 438        ipmi_si.regspacings=<sp1>,<sp2>,...
 439        ipmi_si.regsizes=<size1>,<size2>,...
 440        ipmi_si.regshifts=<shift1>,<shift2>,...
 441        ipmi_si.slave_addrs=<addr1>,<addr2>,...
 442        ipmi_si.force_kipmid=<enable1>,<enable2>,...
 443        ipmi_si.kipmid_max_busy_us=<ustime1>,<ustime2>,...
 444
 445 It works the same as the module parameters of the same names.
 446
 447 By default, the driver will attempt to detect any device specified by
 448 ACPI, and if none of those then a KCS device at the spec-specified
 449 0xca2.  If you want to turn this off, set the "trydefaults" option to
 450 false.
 451
 452 If your IPMI interface does not support interrupts and is a KCS or
 453 SMIC interface, the IPMI driver will start a kernel thread for the
 454 interface to help speed things up.  This is a low-priority kernel
 455 thread that constantly polls the IPMI driver while an IPMI operation
 456 is in progress.  The force_kipmid module parameter will all the user to
 457 force this thread on or off.  If you force it off and don't have
 458 interrupts, the driver will run VERY slowly.  Don't blame me,
 459 these interfaces suck.
 460
 461 Unfortunately, this thread can use a lot of CPU depending on the
 462 interface's performance.  This can waste a lot of CPU and cause
 463 various issues with detecting idle CPU and using extra power.  To
 464 avoid this, the kipmid_max_busy_us sets the maximum amount of time, in
 465 microseconds, that kipmid will spin before sleeping for a tick.  This
 466 value sets a balance between performance and CPU waste and needs to be
 467 tuned to your needs.  Maybe, someday, auto-tuning will be added, but
 468 that's not a simple thing and even the auto-tuning would need to be
 469 tuned to the user's desired performance.
 470
 471 The driver supports a hot add and remove of interfaces.  This way,
 472 interfaces can be added or removed after the kernel is up and running.
 473 This is done using /sys/modules/ipmi_si/parameters/hotmod, which is a
 474 write-only parameter.  You write a string to this interface.  The string
 475 has the format:
 476    <op1>[:op2[:op3...]]
 477 The "op"s are:
 478    add|remove,kcs|bt|smic,mem|i/o,<address>[,<opt1>[,<opt2>[,...]]]
 479 You can specify more than one interface on the line.  The "opt"s are:
 480    rsp=<regspacing>
 481    rsi=<regsize>
 482    rsh=<regshift>
 483    irq=<irq>
 484    ipmb=<ipmb slave addr>
 485 and these have the same meanings as discussed above.  Note that you
 486 can also use this on the kernel command line for a more compact format
 487 for specifying an interface.  Note that when removing an interface,
 488 only the first three parameters (si type, address type, and address)
 489 are used for the comparison.  Any options are ignored for removing.
 490
 491 The SMBus Driver (SSIF)
 492 -----------------------
 493
 494 The SMBus driver allows up to 4 SMBus devices to be configured in the
 495 system.  By default, the driver will only register with something it
 496 finds in DMI or ACPI tables.  You can change this
 497 at module load time (for a module) with:
 498
 499   modprobe ipmi_ssif.o
 500         addr=<i2caddr1>[,<i2caddr2>[,...]]
 501         adapter=<adapter1>[,<adapter2>[...]]
 502         dbg=<flags1>,<flags2>...
 503         slave_addrs=<addr1>,<addr2>,...
 504         [dbg_probe=1]
 505
 506 The addresses are normal I2C addresses.  The adapter is the string
 507 name of the adapter, as shown in /sys/class/i2c-adapter/i2c-<n>/name.
 508 It is *NOT* i2c-<n> itself.
 509
 510 The debug flags are bit flags for each BMC found, they are:
 511 IPMI messages: 1, driver state: 2, timing: 4, I2C probe: 8
 512
 513 Setting dbg_probe to 1 will enable debugging of the probing and
 514 detection process for BMCs on the SMBusses.
 515
 516 The slave_addrs specifies the IPMI address of the local BMC.  This is
 517 usually 0x20 and the driver defaults to that, but in case it's not, it
 518 can be specified when the driver starts up.
 519
 520 Discovering the IPMI compliant BMC on the SMBus can cause devices on
 521 the I2C bus to fail. The SMBus driver writes a "Get Device ID" IPMI
 522 message as a block write to the I2C bus and waits for a response.
 523 This action can be detrimental to some I2C devices. It is highly
 524 recommended that the known I2C address be given to the SMBus driver in
 525 the smb_addr parameter unless you have DMI or ACPI data to tell the
 526 driver what to use.
 527
 528 When compiled into the kernel, the addresses can be specified on the
 529 kernel command line as:
 530
 531   ipmb_ssif.addr=<i2caddr1>[,<i2caddr2>[...]]
 532         ipmi_ssif.adapter=<adapter1>[,<adapter2>[...]]
 533         ipmi_ssif.dbg=<flags1>[,<flags2>[...]]
 534         ipmi_ssif.dbg_probe=1
 535         ipmi_ssif.slave_addrs=<addr1>[,<addr2>[...]]
 536
 537 These are the same options as on the module command line.
 538
 539 The I2C driver does not support non-blocking access or polling, so
 540 this driver cannod to IPMI panic events, extend the watchdog at panic
 541 time, or other panic-related IPMI functions without special kernel
 542 patches and driver modifications.  You can get those at the openipmi
 543 web page.
 544
 545 The driver supports a hot add and remove of interfaces through the I2C
 546 sysfs interface.
 547
 548 Other Pieces
 549 ------------
 550
 551 Get the detailed info related with the IPMI device
 552 --------------------------------------------------
 553
 554 Some users need more detailed information about a device, like where
 555 the address came from or the raw base device for the IPMI interface.
 556 You can use the IPMI smi_watcher to catch the IPMI interfaces as they
 557 come or go, and to grab the information, you can use the function
 558 ipmi_get_smi_info(), which returns the following structure:
 559
 560 struct ipmi_smi_info {
 561         enum ipmi_addr_src addr_src;
 562         struct device *dev;
 563         union {
 564                 struct {
 565                         void *acpi_handle;
 566                 } acpi_info;
 567         } addr_info;
 568 };
 569
 570 Currently special info for only for SI_ACPI address sources is
 571 returned.  Others may be added as necessary.
 572
 573 Note that the dev pointer is included in the above structure, and
 574 assuming ipmi_smi_get_info returns success, you must call put_device
 575 on the dev pointer.
 576
 577
 578 Watchdog
 579 --------
 580
 581 A watchdog timer is provided that implements the Linux-standard
 582 watchdog timer interface.  It has three module parameters that can be
 583 used to control it:
 584
 585   modprobe ipmi_watchdog timeout=<t> pretimeout=<t> action=<action type>
 586       preaction=<preaction type> preop=<preop type> start_now=x
 587       nowayout=x ifnum_to_use=n
 588
 589 ifnum_to_use specifies which interface the watchdog timer should use.
 590 The default is -1, which means to pick the first one registered.
 591
 592 The timeout is the number of seconds to the action, and the pretimeout
 593 is the amount of seconds before the reset that the pre-timeout panic will
 594 occur (if pretimeout is zero, then pretimeout will not be enabled).  Note
 595 that the pretimeout is the time before the final timeout.  So if the
 596 timeout is 50 seconds and the pretimeout is 10 seconds, then the pretimeout
 597 will occur in 40 second (10 seconds before the timeout).
 598
 599 The action may be "reset", "power_cycle", or "power_off", and
 600 specifies what to do when the timer times out, and defaults to
 601 "reset".
 602
 603 The preaction may be "pre_smi" for an indication through the SMI
 604 interface, "pre_int" for an indication through the SMI with an
 605 interrupts, and "pre_nmi" for a NMI on a preaction.  This is how
 606 the driver is informed of the pretimeout.
 607
 608 The preop may be set to "preop_none" for no operation on a pretimeout,
 609 "preop_panic" to set the preoperation to panic, or "preop_give_data"
 610 to provide data to read from the watchdog device when the pretimeout
 611 occurs.  A "pre_nmi" setting CANNOT be used with "preop_give_data"
 612 because you can't do data operations from an NMI.
 613
 614 When preop is set to "preop_give_data", one byte comes ready to read
 615 on the device when the pretimeout occurs.  Select and fasync work on
 616 the device, as well.
 617
 618 If start_now is set to 1, the watchdog timer will start running as
 619 soon as the driver is loaded.
 620
 621 If nowayout is set to 1, the watchdog timer will not stop when the
 622 watchdog device is closed.  The default value of nowayout is true
 623 if the CONFIG_WATCHDOG_NOWAYOUT option is enabled, or false if not.
 624
 625 When compiled into the kernel, the kernel command line is available
 626 for configuring the watchdog:
 627
 628   ipmi_watchdog.timeout=<t> ipmi_watchdog.pretimeout=<t>
 629         ipmi_watchdog.action=<action type>
 630         ipmi_watchdog.preaction=<preaction type>
 631         ipmi_watchdog.preop=<preop type>
 632         ipmi_watchdog.start_now=x
 633         ipmi_watchdog.nowayout=x
 634
 635 The options are the same as the module parameter options.
 636
 637 The watchdog will panic and start a 120 second reset timeout if it
 638 gets a pre-action.  During a panic or a reboot, the watchdog will
 639 start a 120 timer if it is running to make sure the reboot occurs.
 640
 641 Note that if you use the NMI preaction for the watchdog, you MUST NOT
 642 use the nmi watchdog.  There is no reasonable way to tell if an NMI
 643 comes from the IPMI controller, so it must assume that if it gets an
 644 otherwise unhandled NMI, it must be from IPMI and it will panic
 645 immediately.
 646
 647 Once you open the watchdog timer, you must write a 'V' character to the
 648 device to close it, or the timer will not stop.  This is a new semantic
 649 for the driver, but makes it consistent with the rest of the watchdog
 650 drivers in Linux.
 651
 652
 653 Panic Timeouts
 654 --------------
 655
 656 The OpenIPMI driver supports the ability to put semi-custom and custom
 657 events in the system event log if a panic occurs.  if you enable the
 658 'Generate a panic event to all BMCs on a panic' option, you will get
 659 one event on a panic in a standard IPMI event format.  If you enable
 660 the 'Generate OEM events containing the panic string' option, you will
 661 also get a bunch of OEM events holding the panic string.
 662
 663
 664 The field settings of the events are:
 665 * Generator ID: 0x21 (kernel)
 666 * EvM Rev: 0x03 (this event is formatting in IPMI 1.0 format)
 667 * Sensor Type: 0x20 (OS critical stop sensor)
 668 * Sensor #: The first byte of the panic string (0 if no panic string)
 669 * Event Dir | Event Type: 0x6f (Assertion, sensor-specific event info)
 670 * Event Data 1: 0xa1 (Runtime stop in OEM bytes 2 and 3)
 671 * Event data 2: second byte of panic string
 672 * Event data 3: third byte of panic string
 673 See the IPMI spec for the details of the event layout.  This event is
 674 always sent to the local management controller.  It will handle routing
 675 the message to the right place
 676
 677 Other OEM events have the following format:
 678 Record ID (bytes 0-1): Set by the SEL.
 679 Record type (byte 2): 0xf0 (OEM non-timestamped)
 680 byte 3: The slave address of the card saving the panic
 681 byte 4: A sequence number (starting at zero)
 682 The rest of the bytes (11 bytes) are the panic string.  If the panic string
 683 is longer than 11 bytes, multiple messages will be sent with increasing
 684 sequence numbers.
 685
 686 Because you cannot send OEM events using the standard interface, this
 687 function will attempt to find an SEL and add the events there.  It
 688 will first query the capabilities of the local management controller.
 689 If it has an SEL, then they will be stored in the SEL of the local
 690 management controller.  If not, and the local management controller is
 691 an event generator, the event receiver from the local management
 692 controller will be queried and the events sent to the SEL on that
 693 device.  Otherwise, the events go nowhere since there is nowhere to
 694 send them.
 695
 696
 697 Poweroff
 698 --------
 699
 700 If the poweroff capability is selected, the IPMI driver will install
 701 a shutdown function into the standard poweroff function pointer.  This
 702 is in the ipmi_poweroff module.  When the system requests a powerdown,
 703 it will send the proper IPMI commands to do this.  This is supported on
 704 several platforms.
 705
 706 There is a module parameter named "poweroff_powercycle" that may
 707 either be zero (do a power down) or non-zero (do a power cycle, power
 708 the system off, then power it on in a few seconds).  Setting
 709 ipmi_poweroff.poweroff_control=x will do the same thing on the kernel
 710 command line.  The parameter is also available via the proc filesystem
 711 in /proc/sys/dev/ipmi/poweroff_powercycle.  Note that if the system
 712 does not support power cycling, it will always do the power off.
 713
 714 The "ifnum_to_use" parameter specifies which interface the poweroff
 715 code should use.  The default is -1, which means to pick the first one
 716 registered.
 717
 718 Note that if you have ACPI enabled, the system will prefer using ACPI to
 719 power off.