1=====================
2The Linux IPMI Driver
3=====================
4
5:Author: Corey Minyard <minyard@mvista.com> / <minyard@acm.org>
6
7The Intelligent Platform Management Interface, or IPMI, is a
8standard for controlling intelligent devices that monitor a system.
9It provides for dynamic discovery of sensors in the system and the
10ability to monitor the sensors and be informed when the sensor's
11values change or go outside certain boundaries.  It also has a
12standardized database for field-replaceable units (FRUs) and a watchdog
13timer.
14
15To use this, you need an interface to an IPMI controller in your
16system (called a Baseboard Management Controller, or BMC) and
17management software that can use the IPMI system.
18
19This document describes how to use the IPMI driver for Linux.  If you
20are not familiar with IPMI itself, see the web site at
21https://www.intel.com/design/servers/ipmi/index.htm.  IPMI is a big
22subject and I can't cover it all here!
23
24Configuration
25-------------
26
27The Linux IPMI driver is modular, which means you have to pick several
28things to have it work right depending on your hardware.  Most of
29these are available in the 'Character Devices' menu then the IPMI
30menu.
31
32No matter what, you must pick 'IPMI top-level message handler' to use
33IPMI.  What you do beyond that depends on your needs and hardware.
34
35The message handler does not provide any user-level interfaces.
36Kernel code (like the watchdog) can still use it.  If you need access
37from userland, you need to select 'Device interface for IPMI' if you
38want access through a device driver.
39
40The driver interface depends on your hardware.  If your system
41properly provides the SMBIOS info for IPMI, the driver will detect it
42and just work.  If you have a board with a standard interface (These
43will generally be either "KCS", "SMIC", or "BT", consult your hardware
44manual), choose the 'IPMI SI handler' option.  A driver also exists
45for direct I2C access to the IPMI management controller.  Some boards
46support this, but it is unknown if it will work on every board.  For
47this, choose 'IPMI SMBus handler', but be ready to try to do some
48figuring to see if it will work on your system if the SMBIOS/APCI
49information is wrong or not present.  It is fairly safe to have both
50these enabled and let the drivers auto-detect what is present.
51
52You should generally enable ACPI on your system, as systems with IPMI
53can have ACPI tables describing them.
54
55If you have a standard interface and the board manufacturer has done
56their job correctly, the IPMI controller should be automatically
57detected (via ACPI or SMBIOS tables) and should just work.  Sadly,
58many boards do not have this information.  The driver attempts
59standard defaults, but they may not work.  If you fall into this
60situation, you need to read the section below named 'The SI Driver' or
61"The SMBus Driver" on how to hand-configure your system.
62
63IPMI defines a standard watchdog timer.  You can enable this with the
64'IPMI Watchdog Timer' config option.  If you compile the driver into
65the kernel, then via a kernel command-line option you can have the
66watchdog timer start as soon as it initializes.  It also have a lot
67of other options, see the 'Watchdog' section below for more details.
68Note that you can also have the watchdog continue to run if it is
69closed (by default it is disabled on close).  Go into the 'Watchdog
70Cards' menu, enable 'Watchdog Timer Support', and enable the option
71'Disable watchdog shutdown on close'.
72
73IPMI systems can often be powered off using IPMI commands.  Select
74'IPMI Poweroff' to do this.  The driver will auto-detect if the system
75can be powered off by IPMI.  It is safe to enable this even if your
76system doesn't support this option.  This works on ATCA systems, the
77Radisys CPI1 card, and any IPMI system that supports standard chassis
78management commands.
79
80If you want the driver to put an event into the event log on a panic,
81enable the 'Generate a panic event to all BMCs on a panic' option.  If
82you want the whole panic string put into the event log using OEM
83events, enable the 'Generate OEM events containing the panic string'
84option.  You can also enable these dynamically by setting the module
85parameter named "panic_op" in the ipmi_msghandler module to "event"
86or "string".  Setting that parameter to "none" disables this function.
87
88Basic Design
89------------
90
91The Linux IPMI driver is designed to be very modular and flexible, you
92only need to take the pieces you need and you can use it in many
93different ways.  Because of that, it's broken into many chunks of
94code.  These chunks (by module name) are:
95
96ipmi_msghandler - This is the central piece of software for the IPMI
97system.  It handles all messages, message timing, and responses.  The
98IPMI users tie into this, and the IPMI physical interfaces (called
99System Management Interfaces, or SMIs) also tie in here.  This
100provides the kernelland interface for IPMI, but does not provide an
101interface for use by application processes.
102
103ipmi_devintf - This provides a userland IOCTL interface for the IPMI
104driver, each open file for this device ties in to the message handler
105as an IPMI user.
106
107ipmi_si - A driver for various system interfaces.  This supports KCS,
108SMIC, and BT interfaces.  Unless you have an SMBus interface or your
109own custom interface, you probably need to use this.
110
111ipmi_ssif - A driver for accessing BMCs on the SMBus. It uses the
112I2C kernel driver's SMBus interfaces to send and receive IPMI messages
113over the SMBus.
114
115ipmi_powernv - A driver for access BMCs on POWERNV systems.
116
117ipmi_watchdog - IPMI requires systems to have a very capable watchdog
118timer.  This driver implements the standard Linux watchdog timer
119interface on top of the IPMI message handler.
120
121ipmi_poweroff - Some systems support the ability to be turned off via
122IPMI commands.
123
124bt-bmc - This is not part of the main driver, but instead a driver for
125accessing a BMC-side interface of a BT interface.  It is used on BMCs
126running Linux to provide an interface to the host.
127
128These are all individually selectable via configuration options.
129
130Much documentation for the interface is in the include files.  The
131IPMI include files are:
132
133linux/ipmi.h - Contains the user interface and IOCTL interface for IPMI.
134
135linux/ipmi_smi.h - Contains the interface for system management interfaces
136(things that interface to IPMI controllers) to use.
137
138linux/ipmi_msgdefs.h - General definitions for base IPMI messaging.
139
140
141Addressing
142----------
143
144The IPMI addressing works much like IP addresses, you have an overlay
145to handle the different address types.  The overlay is::
146
147  struct ipmi_addr
148  {
149	int   addr_type;
150	short channel;
151	char  data[IPMI_MAX_ADDR_SIZE];
152  };
153
154The addr_type determines what the address really is.  The driver
155currently understands two different types of addresses.
156
157"System Interface" addresses are defined as::
158
159  struct ipmi_system_interface_addr
160  {
161	int   addr_type;
162	short channel;
163  };
164
165and the type is IPMI_SYSTEM_INTERFACE_ADDR_TYPE.  This is used for talking
166straight to the BMC on the current card.  The channel must be
167IPMI_BMC_CHANNEL.
168
169Messages that are destined to go out on the IPMB bus going through the
170BMC use the IPMI_IPMB_ADDR_TYPE address type.  The format is::
171
172  struct ipmi_ipmb_addr
173  {
174	int           addr_type;
175	short         channel;
176	unsigned char slave_addr;
177	unsigned char lun;
178  };
179
180The "channel" here is generally zero, but some devices support more
181than one channel, it corresponds to the channel as defined in the IPMI
182spec.
183
184There is also an IPMB direct address for a situation where the sender
185is directly on an IPMB bus and doesn't have to go through the BMC.
186You can send messages to a specific management controller (MC) on the
187IPMB using the IPMI_IPMB_DIRECT_ADDR_TYPE with the following format::
188
189  struct ipmi_ipmb_direct_addr
190  {
191	int           addr_type;
192	short         channel;
193	unsigned char slave_addr;
194	unsigned char rq_lun;
195	unsigned char rs_lun;
196  };
197
198The channel is always zero.  You can also receive commands from other
199MCs that you have registered to handle and respond to them, so you can
200use this to implement a management controller on a bus..
201
202Messages
203--------
204
205Messages are defined as::
206
207  struct ipmi_msg
208  {
209	unsigned char netfn;
210	unsigned char lun;
211	unsigned char cmd;
212	unsigned char *data;
213	int           data_len;
214  };
215
216The driver takes care of adding/stripping the header information.  The
217data portion is just the data to be send (do NOT put addressing info
218here) or the response.  Note that the completion code of a response is
219the first item in "data", it is not stripped out because that is how
220all the messages are defined in the spec (and thus makes counting the
221offsets a little easier :-).
222
223When using the IOCTL interface from userland, you must provide a block
224of data for "data", fill it, and set data_len to the length of the
225block of data, even when receiving messages.  Otherwise the driver
226will have no place to put the message.
227
228Messages coming up from the message handler in kernelland will come in
229as::
230
231  struct ipmi_recv_msg
232  {
233	struct list_head link;
234
235	/* The type of message as defined in the "Receive Types"
236           defines above. */
237	int         recv_type;
238
239	ipmi_user_t      *user;
240	struct ipmi_addr addr;
241	long             msgid;
242	struct ipmi_msg  msg;
243
244	/* Call this when done with the message.  It will presumably free
245	   the message and do any other necessary cleanup. */
246	void (*done)(struct ipmi_recv_msg *msg);
247
248	/* Place-holder for the data, don't make any assumptions about
249	   the size or existence of this, since it may change. */
250	unsigned char   msg_data[IPMI_MAX_MSG_LENGTH];
251  };
252
253You should look at the receive type and handle the message
254appropriately.
255
256
257The Upper Layer Interface (Message Handler)
258-------------------------------------------
259
260The upper layer of the interface provides the users with a consistent
261view of the IPMI interfaces.  It allows multiple SMI interfaces to be
262addressed (because some boards actually have multiple BMCs on them)
263and the user should not have to care what type of SMI is below them.
264
265
266Watching For Interfaces
267^^^^^^^^^^^^^^^^^^^^^^^
268
269When your code comes up, the IPMI driver may or may not have detected
270if IPMI devices exist.  So you might have to defer your setup until
271the device is detected, or you might be able to do it immediately.
272To handle this, and to allow for discovery, you register an SMI
273watcher with ipmi_smi_watcher_register() to iterate over interfaces
274and tell you when they come and go.
275
276
277Creating the User
278^^^^^^^^^^^^^^^^^
279
280To use the message handler, you must first create a user using
281ipmi_create_user.  The interface number specifies which SMI you want
282to connect to, and you must supply callback functions to be called
283when data comes in.  The callback function can run at interrupt level,
284so be careful using the callbacks.  This also allows to you pass in a
285piece of data, the handler_data, that will be passed back to you on
286all calls.
287
288Once you are done, call ipmi_destroy_user() to get rid of the user.
289
290From userland, opening the device automatically creates a user, and
291closing the device automatically destroys the user.
292
293
294Messaging
295^^^^^^^^^
296
297To send a message from kernel-land, the ipmi_request_settime() call does
298pretty much all message handling.  Most of the parameter are
299self-explanatory.  However, it takes a "msgid" parameter.  This is NOT
300the sequence number of messages.  It is simply a long value that is
301passed back when the response for the message is returned.  You may
302use it for anything you like.
303
304Responses come back in the function pointed to by the ipmi_recv_hndl
305field of the "handler" that you passed in to ipmi_create_user().
306Remember again, these may be running at interrupt level.  Remember to
307look at the receive type, too.
308
309From userland, you fill out an ipmi_req_t structure and use the
310IPMICTL_SEND_COMMAND ioctl.  For incoming stuff, you can use select()
311or poll() to wait for messages to come in.  However, you cannot use
312read() to get them, you must call the IPMICTL_RECEIVE_MSG with the
313ipmi_recv_t structure to actually get the message.  Remember that you
314must supply a pointer to a block of data in the msg.data field, and
315you must fill in the msg.data_len field with the size of the data.
316This gives the receiver a place to actually put the message.
317
318If the message cannot fit into the data you provide, you will get an
319EMSGSIZE error and the driver will leave the data in the receive
320queue.  If you want to get it and have it truncate the message, us
321the IPMICTL_RECEIVE_MSG_TRUNC ioctl.
322
323When you send a command (which is defined by the lowest-order bit of
324the netfn per the IPMI spec) on the IPMB bus, the driver will
325automatically assign the sequence number to the command and save the
326command.  If the response is not receive in the IPMI-specified 5
327seconds, it will generate a response automatically saying the command
328timed out.  If an unsolicited response comes in (if it was after 5
329seconds, for instance), that response will be ignored.
330
331In kernelland, after you receive a message and are done with it, you
332MUST call ipmi_free_recv_msg() on it, or you will leak messages.  Note
333that you should NEVER mess with the "done" field of a message, that is
334required to properly clean up the message.
335
336Note that when sending, there is an ipmi_request_supply_msgs() call
337that lets you supply the smi and receive message.  This is useful for
338pieces of code that need to work even if the system is out of buffers
339(the watchdog timer uses this, for instance).  You supply your own
340buffer and own free routines.  This is not recommended for normal use,
341though, since it is tricky to manage your own buffers.
342
343
344Events and Incoming Commands
345^^^^^^^^^^^^^^^^^^^^^^^^^^^^
346
347The driver takes care of polling for IPMI events and receiving
348commands (commands are messages that are not responses, they are
349commands that other things on the IPMB bus have sent you).  To receive
350these, you must register for them, they will not automatically be sent
351to you.
352
353To receive events, you must call ipmi_set_gets_events() and set the
354"val" to non-zero.  Any events that have been received by the driver
355since startup will immediately be delivered to the first user that
356registers for events.  After that, if multiple users are registered
357for events, they will all receive all events that come in.
358
359For receiving commands, you have to individually register commands you
360want to receive.  Call ipmi_register_for_cmd() and supply the netfn
361and command name for each command you want to receive.  You also
362specify a bitmask of the channels you want to receive the command from
363(or use IPMI_CHAN_ALL for all channels if you don't care).  Only one
364user may be registered for each netfn/cmd/channel, but different users
365may register for different commands, or the same command if the
366channel bitmasks do not overlap.
367
368To respond to a received command, set the response bit in the returned
369netfn, use the address from the received message, and use the same
370msgid that you got in the receive message.
371
372From userland, equivalent IOCTLs are provided to do these functions.
373
374
375The Lower Layer (SMI) Interface
376-------------------------------
377
378As mentioned before, multiple SMI interfaces may be registered to the
379message handler, each of these is assigned an interface number when
380they register with the message handler.  They are generally assigned
381in the order they register, although if an SMI unregisters and then
382another one registers, all bets are off.
383
384The ipmi_smi.h defines the interface for management interfaces, see
385that for more details.
386
387
388The SI Driver
389-------------
390
391The SI driver allows KCS, BT, and SMIC interfaces to be configured
392in the system.  It discovers interfaces through a host of different
393methods, depending on the system.
394
395You can specify up to four interfaces on the module load line and
396control some module parameters::
397
398  modprobe ipmi_si.o type=<type1>,<type2>....
399       ports=<port1>,<port2>... addrs=<addr1>,<addr2>...
400       irqs=<irq1>,<irq2>...
401       regspacings=<sp1>,<sp2>,... regsizes=<size1>,<size2>,...
402       regshifts=<shift1>,<shift2>,...
403       slave_addrs=<addr1>,<addr2>,...
404       force_kipmid=<enable1>,<enable2>,...
405       kipmid_max_busy_us=<ustime1>,<ustime2>,...
406       unload_when_empty=[0|1]
407       trydmi=[0|1] tryacpi=[0|1]
408       tryplatform=[0|1] trypci=[0|1]
409
410Each of these except try... items is a list, the first item for the
411first interface, second item for the second interface, etc.
412
413The si_type may be either "kcs", "smic", or "bt".  If you leave it blank, it
414defaults to "kcs".
415
416If you specify addrs as non-zero for an interface, the driver will
417use the memory address given as the address of the device.  This
418overrides si_ports.
419
420If you specify ports as non-zero for an interface, the driver will
421use the I/O port given as the device address.
422
423If you specify irqs as non-zero for an interface, the driver will
424attempt to use the given interrupt for the device.
425
426The other try... items disable discovery by their corresponding
427names.  These are all enabled by default, set them to zero to disable
428them.  The tryplatform disables openfirmware.
429
430The next three parameters have to do with register layout.  The
431registers used by the interfaces may not appear at successive
432locations and they may not be in 8-bit registers.  These parameters
433allow the layout of the data in the registers to be more precisely
434specified.
435
436The regspacings parameter give the number of bytes between successive
437register start addresses.  For instance, if the regspacing is set to 4
438and the start address is 0xca2, then the address for the second
439register would be 0xca6.  This defaults to 1.
440
441The regsizes parameter gives the size of a register, in bytes.  The
442data used by IPMI is 8-bits wide, but it may be inside a larger
443register.  This parameter allows the read and write type to specified.
444It may be 1, 2, 4, or 8.  The default is 1.
445
446Since the register size may be larger than 32 bits, the IPMI data may not
447be in the lower 8 bits.  The regshifts parameter give the amount to shift
448the data to get to the actual IPMI data.
449
450The slave_addrs specifies the IPMI address of the local BMC.  This is
451usually 0x20 and the driver defaults to that, but in case it's not, it
452can be specified when the driver starts up.
453
454The force_ipmid parameter forcefully enables (if set to 1) or disables
455(if set to 0) the kernel IPMI daemon.  Normally this is auto-detected
456by the driver, but systems with broken interrupts might need an enable,
457or users that don't want the daemon (don't need the performance, don't
458want the CPU hit) can disable it.
459
460If unload_when_empty is set to 1, the driver will be unloaded if it
461doesn't find any interfaces or all the interfaces fail to work.  The
462default is one.  Setting to 0 is useful with the hotmod, but is
463obviously only useful for modules.
464
465When compiled into the kernel, the parameters can be specified on the
466kernel command line as::
467
468  ipmi_si.type=<type1>,<type2>...
469       ipmi_si.ports=<port1>,<port2>... ipmi_si.addrs=<addr1>,<addr2>...
470       ipmi_si.irqs=<irq1>,<irq2>...
471       ipmi_si.regspacings=<sp1>,<sp2>,...
472       ipmi_si.regsizes=<size1>,<size2>,...
473       ipmi_si.regshifts=<shift1>,<shift2>,...
474       ipmi_si.slave_addrs=<addr1>,<addr2>,...
475       ipmi_si.force_kipmid=<enable1>,<enable2>,...
476       ipmi_si.kipmid_max_busy_us=<ustime1>,<ustime2>,...
477
478It works the same as the module parameters of the same names.
479
480If your IPMI interface does not support interrupts and is a KCS or
481SMIC interface, the IPMI driver will start a kernel thread for the
482interface to help speed things up.  This is a low-priority kernel
483thread that constantly polls the IPMI driver while an IPMI operation
484is in progress.  The force_kipmid module parameter will all the user to
485force this thread on or off.  If you force it off and don't have
486interrupts, the driver will run VERY slowly.  Don't blame me,
487these interfaces suck.
488
489Unfortunately, this thread can use a lot of CPU depending on the
490interface's performance.  This can waste a lot of CPU and cause
491various issues with detecting idle CPU and using extra power.  To
492avoid this, the kipmid_max_busy_us sets the maximum amount of time, in
493microseconds, that kipmid will spin before sleeping for a tick.  This
494value sets a balance between performance and CPU waste and needs to be
495tuned to your needs.  Maybe, someday, auto-tuning will be added, but
496that's not a simple thing and even the auto-tuning would need to be
497tuned to the user's desired performance.
498
499The driver supports a hot add and remove of interfaces.  This way,
500interfaces can be added or removed after the kernel is up and running.
501This is done using /sys/modules/ipmi_si/parameters/hotmod, which is a
502write-only parameter.  You write a string to this interface.  The string
503has the format::
504
505   <op1>[:op2[:op3...]]
506
507The "op"s are::
508
509   add|remove,kcs|bt|smic,mem|i/o,<address>[,<opt1>[,<opt2>[,...]]]
510
511You can specify more than one interface on the line.  The "opt"s are::
512
513   rsp=<regspacing>
514   rsi=<regsize>
515   rsh=<regshift>
516   irq=<irq>
517   ipmb=<ipmb slave addr>
518
519and these have the same meanings as discussed above.  Note that you
520can also use this on the kernel command line for a more compact format
521for specifying an interface.  Note that when removing an interface,
522only the first three parameters (si type, address type, and address)
523are used for the comparison.  Any options are ignored for removing.
524
525The SMBus Driver (SSIF)
526-----------------------
527
528The SMBus driver allows up to 4 SMBus devices to be configured in the
529system.  By default, the driver will only register with something it
530finds in DMI or ACPI tables.  You can change this
531at module load time (for a module) with::
532
533  modprobe ipmi_ssif.o
534	addr=<i2caddr1>[,<i2caddr2>[,...]]
535	adapter=<adapter1>[,<adapter2>[...]]
536	dbg=<flags1>,<flags2>...
537	slave_addrs=<addr1>,<addr2>,...
538	tryacpi=[0|1] trydmi=[0|1]
539	[dbg_probe=1]
540	alerts_broken
541
542The addresses are normal I2C addresses.  The adapter is the string
543name of the adapter, as shown in /sys/class/i2c-adapter/i2c-<n>/name.
544It is *NOT* i2c-<n> itself.  Also, the comparison is done ignoring
545spaces, so if the name is "This is an I2C chip" you can say
546adapter_name=ThisisanI2cchip.  This is because it's hard to pass in
547spaces in kernel parameters.
548
549The debug flags are bit flags for each BMC found, they are:
550IPMI messages: 1, driver state: 2, timing: 4, I2C probe: 8
551
552The tryxxx parameters can be used to disable detecting interfaces
553from various sources.
554
555Setting dbg_probe to 1 will enable debugging of the probing and
556detection process for BMCs on the SMBusses.
557
558The slave_addrs specifies the IPMI address of the local BMC.  This is
559usually 0x20 and the driver defaults to that, but in case it's not, it
560can be specified when the driver starts up.
561
562alerts_broken does not enable SMBus alert for SSIF. Otherwise SMBus
563alert will be enabled on supported hardware.
564
565Discovering the IPMI compliant BMC on the SMBus can cause devices on
566the I2C bus to fail. The SMBus driver writes a "Get Device ID" IPMI
567message as a block write to the I2C bus and waits for a response.
568This action can be detrimental to some I2C devices. It is highly
569recommended that the known I2C address be given to the SMBus driver in
570the smb_addr parameter unless you have DMI or ACPI data to tell the
571driver what to use.
572
573When compiled into the kernel, the addresses can be specified on the
574kernel command line as::
575
576  ipmb_ssif.addr=<i2caddr1>[,<i2caddr2>[...]]
577	ipmi_ssif.adapter=<adapter1>[,<adapter2>[...]]
578	ipmi_ssif.dbg=<flags1>[,<flags2>[...]]
579	ipmi_ssif.dbg_probe=1
580	ipmi_ssif.slave_addrs=<addr1>[,<addr2>[...]]
581	ipmi_ssif.tryacpi=[0|1] ipmi_ssif.trydmi=[0|1]
582
583These are the same options as on the module command line.
584
585The I2C driver does not support non-blocking access or polling, so
586this driver cannod to IPMI panic events, extend the watchdog at panic
587time, or other panic-related IPMI functions without special kernel
588patches and driver modifications.  You can get those at the openipmi
589web page.
590
591The driver supports a hot add and remove of interfaces through the I2C
592sysfs interface.
593
594The IPMI IPMB Driver
595--------------------
596
597This driver is for supporting a system that sits on an IPMB bus; it
598allows the interface to look like a normal IPMI interface.  Sending
599system interface addressed messages to it will cause the message to go
600to the registered BMC on the system (default at IPMI address 0x20).
601
602It also allows you to directly address other MCs on the bus using the
603ipmb direct addressing.  You can receive commands from other MCs on
604the bus and they will be handled through the normal received command
605mechanism described above.
606
607Parameters are::
608
609  ipmi_ipmb.bmcaddr=<address to use for system interface addresses messages>
610	ipmi_ipmb.retry_time_ms=<Time between retries on IPMB>
611	ipmi_ipmb.max_retries=<Number of times to retry a message>
612
613Loading the module will not result in the driver automatcially
614starting unless there is device tree information setting it up.  If
615you want to instantiate one of these by hand, do::
616
617  echo ipmi-ipmb <addr> > /sys/class/i2c-dev/i2c-<n>/device/new_device
618
619Note that the address you give here is the I2C address, not the IPMI
620address.  So if you want your MC address to be 0x60, you put 0x30
621here.  See the I2C driver info for more details.
622
623Command bridging to other IPMB busses through this interface does not
624work.  The receive message queue is not implemented, by design.  There
625is only one receive message queue on a BMC, and that is meant for the
626host drivers, not something on the IPMB bus.
627
628A BMC may have multiple IPMB busses, which bus your device sits on
629depends on how the system is wired.  You can fetch the channels with
630"ipmitool channel info <n>" where <n> is the channel, with the
631channels being 0-7 and try the IPMB channels.
632
633Other Pieces
634------------
635
636Get the detailed info related with the IPMI device
637--------------------------------------------------
638
639Some users need more detailed information about a device, like where
640the address came from or the raw base device for the IPMI interface.
641You can use the IPMI smi_watcher to catch the IPMI interfaces as they
642come or go, and to grab the information, you can use the function
643ipmi_get_smi_info(), which returns the following structure::
644
645  struct ipmi_smi_info {
646	enum ipmi_addr_src addr_src;
647	struct device *dev;
648	union {
649		struct {
650			void *acpi_handle;
651		} acpi_info;
652	} addr_info;
653  };
654
655Currently special info for only for SI_ACPI address sources is
656returned.  Others may be added as necessary.
657
658Note that the dev pointer is included in the above structure, and
659assuming ipmi_smi_get_info returns success, you must call put_device
660on the dev pointer.
661
662
663Watchdog
664--------
665
666A watchdog timer is provided that implements the Linux-standard
667watchdog timer interface.  It has three module parameters that can be
668used to control it::
669
670  modprobe ipmi_watchdog timeout=<t> pretimeout=<t> action=<action type>
671      preaction=<preaction type> preop=<preop type> start_now=x
672      nowayout=x ifnum_to_use=n panic_wdt_timeout=<t>
673
674ifnum_to_use specifies which interface the watchdog timer should use.
675The default is -1, which means to pick the first one registered.
676
677The timeout is the number of seconds to the action, and the pretimeout
678is the amount of seconds before the reset that the pre-timeout panic will
679occur (if pretimeout is zero, then pretimeout will not be enabled).  Note
680that the pretimeout is the time before the final timeout.  So if the
681timeout is 50 seconds and the pretimeout is 10 seconds, then the pretimeout
682will occur in 40 second (10 seconds before the timeout). The panic_wdt_timeout
683is the value of timeout which is set on kernel panic, in order to let actions
684such as kdump to occur during panic.
685
686The action may be "reset", "power_cycle", or "power_off", and
687specifies what to do when the timer times out, and defaults to
688"reset".
689
690The preaction may be "pre_smi" for an indication through the SMI
691interface, "pre_int" for an indication through the SMI with an
692interrupts, and "pre_nmi" for a NMI on a preaction.  This is how
693the driver is informed of the pretimeout.
694
695The preop may be set to "preop_none" for no operation on a pretimeout,
696"preop_panic" to set the preoperation to panic, or "preop_give_data"
697to provide data to read from the watchdog device when the pretimeout
698occurs.  A "pre_nmi" setting CANNOT be used with "preop_give_data"
699because you can't do data operations from an NMI.
700
701When preop is set to "preop_give_data", one byte comes ready to read
702on the device when the pretimeout occurs.  Select and fasync work on
703the device, as well.
704
705If start_now is set to 1, the watchdog timer will start running as
706soon as the driver is loaded.
707
708If nowayout is set to 1, the watchdog timer will not stop when the
709watchdog device is closed.  The default value of nowayout is true
710if the CONFIG_WATCHDOG_NOWAYOUT option is enabled, or false if not.
711
712When compiled into the kernel, the kernel command line is available
713for configuring the watchdog::
714
715  ipmi_watchdog.timeout=<t> ipmi_watchdog.pretimeout=<t>
716	ipmi_watchdog.action=<action type>
717	ipmi_watchdog.preaction=<preaction type>
718	ipmi_watchdog.preop=<preop type>
719	ipmi_watchdog.start_now=x
720	ipmi_watchdog.nowayout=x
721	ipmi_watchdog.panic_wdt_timeout=<t>
722
723The options are the same as the module parameter options.
724
725The watchdog will panic and start a 120 second reset timeout if it
726gets a pre-action.  During a panic or a reboot, the watchdog will
727start a 120 timer if it is running to make sure the reboot occurs.
728
729Note that if you use the NMI preaction for the watchdog, you MUST NOT
730use the nmi watchdog.  There is no reasonable way to tell if an NMI
731comes from the IPMI controller, so it must assume that if it gets an
732otherwise unhandled NMI, it must be from IPMI and it will panic
733immediately.
734
735Once you open the watchdog timer, you must write a 'V' character to the
736device to close it, or the timer will not stop.  This is a new semantic
737for the driver, but makes it consistent with the rest of the watchdog
738drivers in Linux.
739
740
741Panic Timeouts
742--------------
743
744The OpenIPMI driver supports the ability to put semi-custom and custom
745events in the system event log if a panic occurs.  if you enable the
746'Generate a panic event to all BMCs on a panic' option, you will get
747one event on a panic in a standard IPMI event format.  If you enable
748the 'Generate OEM events containing the panic string' option, you will
749also get a bunch of OEM events holding the panic string.
750
751
752The field settings of the events are:
753
754* Generator ID: 0x21 (kernel)
755* EvM Rev: 0x03 (this event is formatting in IPMI 1.0 format)
756* Sensor Type: 0x20 (OS critical stop sensor)
757* Sensor #: The first byte of the panic string (0 if no panic string)
758* Event Dir | Event Type: 0x6f (Assertion, sensor-specific event info)
759* Event Data 1: 0xa1 (Runtime stop in OEM bytes 2 and 3)
760* Event data 2: second byte of panic string
761* Event data 3: third byte of panic string
762
763See the IPMI spec for the details of the event layout.  This event is
764always sent to the local management controller.  It will handle routing
765the message to the right place
766
767Other OEM events have the following format:
768
769* Record ID (bytes 0-1): Set by the SEL.
770* Record type (byte 2): 0xf0 (OEM non-timestamped)
771* byte 3: The slave address of the card saving the panic
772* byte 4: A sequence number (starting at zero)
773  The rest of the bytes (11 bytes) are the panic string.  If the panic string
774  is longer than 11 bytes, multiple messages will be sent with increasing
775  sequence numbers.
776
777Because you cannot send OEM events using the standard interface, this
778function will attempt to find an SEL and add the events there.  It
779will first query the capabilities of the local management controller.
780If it has an SEL, then they will be stored in the SEL of the local
781management controller.  If not, and the local management controller is
782an event generator, the event receiver from the local management
783controller will be queried and the events sent to the SEL on that
784device.  Otherwise, the events go nowhere since there is nowhere to
785send them.
786
787
788Poweroff
789--------
790
791If the poweroff capability is selected, the IPMI driver will install
792a shutdown function into the standard poweroff function pointer.  This
793is in the ipmi_poweroff module.  When the system requests a powerdown,
794it will send the proper IPMI commands to do this.  This is supported on
795several platforms.
796
797There is a module parameter named "poweroff_powercycle" that may
798either be zero (do a power down) or non-zero (do a power cycle, power
799the system off, then power it on in a few seconds).  Setting
800ipmi_poweroff.poweroff_control=x will do the same thing on the kernel
801command line.  The parameter is also available via the proc filesystem
802in /proc/sys/dev/ipmi/poweroff_powercycle.  Note that if the system
803does not support power cycling, it will always do the power off.
804
805The "ifnum_to_use" parameter specifies which interface the poweroff
806code should use.  The default is -1, which means to pick the first one
807registered.
808
809Note that if you have ACPI enabled, the system will prefer using ACPI to
810power off.
811