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1
2 The Linux IPMI Driver
3 ---------------------
4 Corey Minyard
5 <minyard@mvista.com>
6 <minyard@acm.org>
7
8The Intelligent Platform Management Interface, or IPMI, is a
9standard for controlling intelligent devices that monitor a system.
10It provides for dynamic discovery of sensors in the system and the
11ability to monitor the sensors and be informed when the sensor's
12values change or go outside certain boundaries. It also has a
dc474c89 13standardized database for field-replaceable units (FRUs) and a watchdog
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14timer.
15
16To use this, you need an interface to an IPMI controller in your
17system (called a Baseboard Management Controller, or BMC) and
18management software that can use the IPMI system.
19
20This document describes how to use the IPMI driver for Linux. If you
21are not familiar with IPMI itself, see the web site at
22http://www.intel.com/design/servers/ipmi/index.htm. IPMI is a big
23subject and I can't cover it all here!
24
25Configuration
26-------------
27
845e78a1 28The Linux IPMI driver is modular, which means you have to pick several
1da177e4 29things to have it work right depending on your hardware. Most of
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30these are available in the 'Character Devices' menu then the IPMI
31menu.
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32
33No matter what, you must pick 'IPMI top-level message handler' to use
34IPMI. What you do beyond that depends on your needs and hardware.
35
36The message handler does not provide any user-level interfaces.
37Kernel code (like the watchdog) can still use it. If you need access
38from userland, you need to select 'Device interface for IPMI' if you
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39want access through a device driver.
40
41The driver interface depends on your hardware. If your system
42properly provides the SMBIOS info for IPMI, the driver will detect it
43and just work. If you have a board with a standard interface (These
44will generally be either "KCS", "SMIC", or "BT", consult your hardware
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45manual), choose the 'IPMI SI handler' option. A driver also exists
46for direct I2C access to the IPMI management controller. Some boards
47support this, but it is unknown if it will work on every board. For
48this, choose 'IPMI SMBus handler', but be ready to try to do some
49figuring to see if it will work on your system if the SMBIOS/APCI
50information is wrong or not present. It is fairly safe to have both
51these enabled and let the drivers auto-detect what is present.
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52
53You should generally enable ACPI on your system, as systems with IPMI
845e78a1 54can have ACPI tables describing them.
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55
56If you have a standard interface and the board manufacturer has done
57their job correctly, the IPMI controller should be automatically
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58detected (via ACPI or SMBIOS tables) and should just work. Sadly,
59many boards do not have this information. The driver attempts
60standard defaults, but they may not work. If you fall into this
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61situation, you need to read the section below named 'The SI Driver' or
62"The SMBus Driver" on how to hand-configure your system.
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63
64IPMI defines a standard watchdog timer. You can enable this with the
65'IPMI Watchdog Timer' config option. If you compile the driver into
66the kernel, then via a kernel command-line option you can have the
dc474c89 67watchdog timer start as soon as it initializes. It also have a lot
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68of other options, see the 'Watchdog' section below for more details.
69Note that you can also have the watchdog continue to run if it is
70closed (by default it is disabled on close). Go into the 'Watchdog
71Cards' menu, enable 'Watchdog Timer Support', and enable the option
72'Disable watchdog shutdown on close'.
73
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74IPMI systems can often be powered off using IPMI commands. Select
75'IPMI Poweroff' to do this. The driver will auto-detect if the system
76can be powered off by IPMI. It is safe to enable this even if your
77system doesn't support this option. This works on ATCA systems, the
78Radisys CPI1 card, and any IPMI system that supports standard chassis
79management commands.
80
81If you want the driver to put an event into the event log on a panic,
82enable the 'Generate a panic event to all BMCs on a panic' option. If
83you want the whole panic string put into the event log using OEM
84events, enable the 'Generate OEM events containing the panic string'
85option.
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86
87Basic Design
88------------
89
90The Linux IPMI driver is designed to be very modular and flexible, you
91only need to take the pieces you need and you can use it in many
92different ways. Because of that, it's broken into many chunks of
845e78a1 93code. These chunks (by module name) are:
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94
95ipmi_msghandler - This is the central piece of software for the IPMI
96system. It handles all messages, message timing, and responses. The
97IPMI users tie into this, and the IPMI physical interfaces (called
98System Management Interfaces, or SMIs) also tie in here. This
99provides the kernelland interface for IPMI, but does not provide an
100interface for use by application processes.
101
102ipmi_devintf - This provides a userland IOCTL interface for the IPMI
103driver, each open file for this device ties in to the message handler
104as an IPMI user.
105
845e78a1 106ipmi_si - A driver for various system interfaces. This supports KCS,
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107SMIC, and BT interfaces. Unless you have an SMBus interface or your
108own custom interface, you probably need to use this.
109
110ipmi_ssif - A driver for accessing BMCs on the SMBus. It uses the
111I2C kernel driver's SMBus interfaces to send and receive IPMI messages
112over the SMBus.
1da177e4 113
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114ipmi_watchdog - IPMI requires systems to have a very capable watchdog
115timer. This driver implements the standard Linux watchdog timer
116interface on top of the IPMI message handler.
117
118ipmi_poweroff - Some systems support the ability to be turned off via
119IPMI commands.
120
121These are all individually selectable via configuration options.
1da177e4 122
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123Note that the KCS-only interface has been removed. The af_ipmi driver
124is no longer supported and has been removed because it was impossible
125to do 32 bit emulation on 64-bit kernels with it.
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126
127Much documentation for the interface is in the include files. The
128IPMI include files are:
129
130net/af_ipmi.h - Contains the socket interface.
131
132linux/ipmi.h - Contains the user interface and IOCTL interface for IPMI.
133
134linux/ipmi_smi.h - Contains the interface for system management interfaces
135(things that interface to IPMI controllers) to use.
136
137linux/ipmi_msgdefs.h - General definitions for base IPMI messaging.
138
139
140Addressing
141----------
142
143The IPMI addressing works much like IP addresses, you have an overlay
144to 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
153The addr_type determines what the address really is. The driver
154currently 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
164and the type is IPMI_SYSTEM_INTERFACE_ADDR_TYPE. This is used for talking
165straight to the BMC on the current card. The channel must be
166IPMI_BMC_CHANNEL.
167
168Messages that are destined to go out on the IPMB bus use the
169IPMI_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
179The "channel" here is generally zero, but some devices support more
180than one channel, it corresponds to the channel as defined in the IPMI
181spec.
182
183
184Messages
185--------
186
187Messages are defined as:
188
189struct 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
198The driver takes care of adding/stripping the header information. The
199data portion is just the data to be send (do NOT put addressing info
200here) or the response. Note that the completion code of a response is
201the first item in "data", it is not stripped out because that is how
202all the messages are defined in the spec (and thus makes counting the
203offsets a little easier :-).
204
205When using the IOCTL interface from userland, you must provide a block
206of data for "data", fill it, and set data_len to the length of the
207block of data, even when receiving messages. Otherwise the driver
208will have no place to put the message.
209
210Messages coming up from the message handler in kernelland will come in
211as:
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
235You should look at the receive type and handle the message
236appropriately.
237
238
239The Upper Layer Interface (Message Handler)
240-------------------------------------------
241
242The upper layer of the interface provides the users with a consistent
243view of the IPMI interfaces. It allows multiple SMI interfaces to be
244addressed (because some boards actually have multiple BMCs on them)
245and the user should not have to care what type of SMI is below them.
246
247
248Creating the User
249
250To user the message handler, you must first create a user using
251ipmi_create_user. The interface number specifies which SMI you want
252to connect to, and you must supply callback functions to be called
253when data comes in. The callback function can run at interrupt level,
254so be careful using the callbacks. This also allows to you pass in a
255piece of data, the handler_data, that will be passed back to you on
256all calls.
257
258Once you are done, call ipmi_destroy_user() to get rid of the user.
259
260From userland, opening the device automatically creates a user, and
261closing the device automatically destroys the user.
262
263
264Messaging
265
266To send a message from kernel-land, the ipmi_request() call does
267pretty much all message handling. Most of the parameter are
268self-explanatory. However, it takes a "msgid" parameter. This is NOT
269the sequence number of messages. It is simply a long value that is
270passed back when the response for the message is returned. You may
271use it for anything you like.
272
273Responses come back in the function pointed to by the ipmi_recv_hndl
274field of the "handler" that you passed in to ipmi_create_user().
275Remember again, these may be running at interrupt level. Remember to
276look at the receive type, too.
277
278From userland, you fill out an ipmi_req_t structure and use the
279IPMICTL_SEND_COMMAND ioctl. For incoming stuff, you can use select()
280or poll() to wait for messages to come in. However, you cannot use
281read() to get them, you must call the IPMICTL_RECEIVE_MSG with the
282ipmi_recv_t structure to actually get the message. Remember that you
283must supply a pointer to a block of data in the msg.data field, and
284you must fill in the msg.data_len field with the size of the data.
285This gives the receiver a place to actually put the message.
286
287If the message cannot fit into the data you provide, you will get an
288EMSGSIZE error and the driver will leave the data in the receive
289queue. If you want to get it and have it truncate the message, us
290the IPMICTL_RECEIVE_MSG_TRUNC ioctl.
291
292When you send a command (which is defined by the lowest-order bit of
293the netfn per the IPMI spec) on the IPMB bus, the driver will
294automatically assign the sequence number to the command and save the
295command. If the response is not receive in the IPMI-specified 5
296seconds, it will generate a response automatically saying the command
297timed out. If an unsolicited response comes in (if it was after 5
298seconds, for instance), that response will be ignored.
299
300In kernelland, after you receive a message and are done with it, you
301MUST call ipmi_free_recv_msg() on it, or you will leak messages. Note
302that you should NEVER mess with the "done" field of a message, that is
303required to properly clean up the message.
304
305Note that when sending, there is an ipmi_request_supply_msgs() call
306that lets you supply the smi and receive message. This is useful for
307pieces 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
309buffer and own free routines. This is not recommended for normal use,
310though, since it is tricky to manage your own buffers.
311
312
313Events and Incoming Commands
314
315The driver takes care of polling for IPMI events and receiving
316commands (commands are messages that are not responses, they are
317commands that other things on the IPMB bus have sent you). To receive
318these, you must register for them, they will not automatically be sent
319to you.
320
321To 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
323since startup will immediately be delivered to the first user that
324registers for events. After that, if multiple users are registered
325for events, they will all receive all events that come in.
326
327For receiving commands, you have to individually register commands you
328want to receive. Call ipmi_register_for_cmd() and supply the netfn
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329and command name for each command you want to receive. You also
330specify 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
332user may be registered for each netfn/cmd/channel, but different users
333may register for different commands, or the same command if the
334channel bitmasks do not overlap.
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335
336From userland, equivalent IOCTLs are provided to do these functions.
337
338
339The Lower Layer (SMI) Interface
340-------------------------------
341
342As mentioned before, multiple SMI interfaces may be registered to the
343message handler, each of these is assigned an interface number when
344they register with the message handler. They are generally assigned
345in the order they register, although if an SMI unregisters and then
346another one registers, all bets are off.
347
348The ipmi_smi.h defines the interface for management interfaces, see
349that for more details.
350
351
352The SI Driver
353-------------
354
355The SI driver allows up to 4 KCS or SMIC interfaces to be configured
356in the system. By default, scan the ACPI tables for interfaces, and
357if it doesn't find any the driver will attempt to register one KCS
358interface at the spec-specified I/O port 0xca2 without interrupts.
359You 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>...
f2afae46 363 irqs=<irq1>,<irq2>...
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364 regspacings=<sp1>,<sp2>,... regsizes=<size1>,<size2>,...
365 regshifts=<shift1>,<shift2>,...
366 slave_addrs=<addr1>,<addr2>,...
a51f4a81 367 force_kipmid=<enable1>,<enable2>,...
ae74e823 368 kipmid_max_busy_us=<ustime1>,<ustime2>,...
b361e27b 369 unload_when_empty=[0|1]
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370 trydefaults=[0|1] trydmi=[0|1] tryacpi=[0|1]
371 tryplatform=[0|1] trypci=[0|1]
1da177e4 372
f2afae46 373Each of these except try... items is a list, the first item for the
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374first interface, second item for the second interface, etc.
375
376The si_type may be either "kcs", "smic", or "bt". If you leave it blank, it
377defaults to "kcs".
378
f2afae46 379If you specify addrs as non-zero for an interface, the driver will
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380use the memory address given as the address of the device. This
381overrides si_ports.
382
f2afae46 383If you specify ports as non-zero for an interface, the driver will
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384use the I/O port given as the device address.
385
f2afae46 386If you specify irqs as non-zero for an interface, the driver will
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387attempt to use the given interrupt for the device.
388
f2afae46 389trydefaults sets whether the standard IPMI interface at 0xca2 and
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390any interfaces specified by ACPE are tried. By default, the driver
391tries it, set this value to zero to turn this off.
392
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393The other try... items disable discovery by their corresponding
394names. These are all enabled by default, set them to zero to disable
395them. The tryplatform disables openfirmware.
396
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397The next three parameters have to do with register layout. The
398registers used by the interfaces may not appear at successive
399locations and they may not be in 8-bit registers. These parameters
400allow the layout of the data in the registers to be more precisely
401specified.
402
403The regspacings parameter give the number of bytes between successive
404register start addresses. For instance, if the regspacing is set to 4
405and the start address is 0xca2, then the address for the second
406register would be 0xca6. This defaults to 1.
407
408The regsizes parameter gives the size of a register, in bytes. The
409data used by IPMI is 8-bits wide, but it may be inside a larger
410register. This parameter allows the read and write type to specified.
411It may be 1, 2, 4, or 8. The default is 1.
412
413Since the register size may be larger than 32 bits, the IPMI data may not
414be in the lower 8 bits. The regshifts parameter give the amount to shift
415the data to get to the actual IPMI data.
416
417The slave_addrs specifies the IPMI address of the local BMC. This is
418usually 0x20 and the driver defaults to that, but in case it's not, it
419can be specified when the driver starts up.
420
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421The 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
423by the driver, but systems with broken interrupts might need an enable,
424or users that don't want the daemon (don't need the performance, don't
425want the CPU hit) can disable it.
426
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427If unload_when_empty is set to 1, the driver will be unloaded if it
428doesn't find any interfaces or all the interfaces fail to work. The
429default is one. Setting to 0 is useful with the hotmod, but is
430obviously only useful for modules.
431
a51f4a81 432When compiled into the kernel, the parameters can be specified on the
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433kernel 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>,...
a51f4a81 442 ipmi_si.force_kipmid=<enable1>,<enable2>,...
ae74e823 443 ipmi_si.kipmid_max_busy_us=<ustime1>,<ustime2>,...
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444
445It works the same as the module parameters of the same names.
446
447By default, the driver will attempt to detect any device specified by
448ACPI, and if none of those then a KCS device at the spec-specified
4490xca2. If you want to turn this off, set the "trydefaults" option to
450false.
451
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452If your IPMI interface does not support interrupts and is a KCS or
453SMIC interface, the IPMI driver will start a kernel thread for the
454interface to help speed things up. This is a low-priority kernel
455thread that constantly polls the IPMI driver while an IPMI operation
456is in progress. The force_kipmid module parameter will all the user to
457force this thread on or off. If you force it off and don't have
458interrupts, the driver will run VERY slowly. Don't blame me,
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459these interfaces suck.
460
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461Unfortunately, this thread can use a lot of CPU depending on the
462interface's performance. This can waste a lot of CPU and cause
463various issues with detecting idle CPU and using extra power. To
464avoid this, the kipmid_max_busy_us sets the maximum amount of time, in
465microseconds, that kipmid will spin before sleeping for a tick. This
466value sets a balance between performance and CPU waste and needs to be
467tuned to your needs. Maybe, someday, auto-tuning will be added, but
468that's not a simple thing and even the auto-tuning would need to be
469tuned to the user's desired performance.
470
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471The driver supports a hot add and remove of interfaces. This way,
472interfaces can be added or removed after the kernel is up and running.
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473This is done using /sys/modules/ipmi_si/parameters/hotmod, which is a
474write-only parameter. You write a string to this interface. The string
475has the format:
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476 <op1>[:op2[:op3...]]
477The "op"s are:
478 add|remove,kcs|bt|smic,mem|i/o,<address>[,<opt1>[,<opt2>[,...]]]
479You 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>
485and these have the same meanings as discussed above. Note that you
486can also use this on the kernel command line for a more compact format
487for specifying an interface. Note that when removing an interface,
488only the first three parameters (si type, address type, and address)
489are used for the comparison. Any options are ignored for removing.
1da177e4 490
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491The SMBus Driver (SSIF)
492-----------------------
493
494The SMBus driver allows up to 4 SMBus devices to be configured in the
495system. By default, the driver will only register with something it
496finds in DMI or ACPI tables. You can change this
497at 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
506The addresses are normal I2C addresses. The adapter is the string
507name of the adapter, as shown in /sys/class/i2c-adapter/i2c-<n>/name.
508It is *NOT* i2c-<n> itself.
509
510The debug flags are bit flags for each BMC found, they are:
511IPMI messages: 1, driver state: 2, timing: 4, I2C probe: 8
512
513Setting dbg_probe to 1 will enable debugging of the probing and
514detection process for BMCs on the SMBusses.
515
516The slave_addrs specifies the IPMI address of the local BMC. This is
517usually 0x20 and the driver defaults to that, but in case it's not, it
518can be specified when the driver starts up.
519
520Discovering the IPMI compliant BMC on the SMBus can cause devices on
521the I2C bus to fail. The SMBus driver writes a "Get Device ID" IPMI
522message as a block write to the I2C bus and waits for a response.
523This action can be detrimental to some I2C devices. It is highly
524recommended that the known I2C address be given to the SMBus driver in
525the smb_addr parameter unless you have DMI or ACPI data to tell the
526driver what to use.
527
528When compiled into the kernel, the addresses can be specified on the
529kernel 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
537These are the same options as on the module command line.
538
539The I2C driver does not support non-blocking access or polling, so
540this driver cannod to IPMI panic events, extend the watchdog at panic
541time, or other panic-related IPMI functions without special kernel
542patches and driver modifications. You can get those at the openipmi
543web page.
544
545The driver supports a hot add and remove of interfaces through the I2C
546sysfs interface.
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547
548Other Pieces
549------------
550
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551Get the detailed info related with the IPMI device
552--------------------------------------------------
553
554Some users need more detailed information about a device, like where
555the address came from or the raw base device for the IPMI interface.
556You can use the IPMI smi_watcher to catch the IPMI interfaces as they
557come or go, and to grab the information, you can use the function
558ipmi_get_smi_info(), which returns the following structure:
559
560struct 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
570Currently special info for only for SI_ACPI address sources is
571returned. Others may be added as necessary.
572
573Note that the dev pointer is included in the above structure, and
574assuming ipmi_smi_get_info returns success, you must call put_device
575on the dev pointer.
576
577
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578Watchdog
579--------
580
581A watchdog timer is provided that implements the Linux-standard
582watchdog timer interface. It has three module parameters that can be
583used 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
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587 nowayout=x ifnum_to_use=n
588
589ifnum_to_use specifies which interface the watchdog timer should use.
590The default is -1, which means to pick the first one registered.
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591
592The timeout is the number of seconds to the action, and the pretimeout
593is the amount of seconds before the reset that the pre-timeout panic will
594occur (if pretimeout is zero, then pretimeout will not be enabled). Note
595that the pretimeout is the time before the final timeout. So if the
596timeout is 50 seconds and the pretimeout is 10 seconds, then the pretimeout
597will occur in 40 second (10 seconds before the timeout).
598
599The action may be "reset", "power_cycle", or "power_off", and
600specifies what to do when the timer times out, and defaults to
601"reset".
602
603The preaction may be "pre_smi" for an indication through the SMI
604interface, "pre_int" for an indication through the SMI with an
605interrupts, and "pre_nmi" for a NMI on a preaction. This is how
606the driver is informed of the pretimeout.
607
608The 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"
610to provide data to read from the watchdog device when the pretimeout
611occurs. A "pre_nmi" setting CANNOT be used with "preop_give_data"
612because you can't do data operations from an NMI.
613
614When preop is set to "preop_give_data", one byte comes ready to read
615on the device when the pretimeout occurs. Select and fasync work on
616the device, as well.
617
618If start_now is set to 1, the watchdog timer will start running as
619soon as the driver is loaded.
620
621If nowayout is set to 1, the watchdog timer will not stop when the
622watchdog device is closed. The default value of nowayout is true
623if the CONFIG_WATCHDOG_NOWAYOUT option is enabled, or false if not.
624
625When compiled into the kernel, the kernel command line is available
626for 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
635The options are the same as the module parameter options.
636
637The watchdog will panic and start a 120 second reset timeout if it
638gets a pre-action. During a panic or a reboot, the watchdog will
639start a 120 timer if it is running to make sure the reboot occurs.
640
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641Note that if you use the NMI preaction for the watchdog, you MUST NOT
642use the nmi watchdog. There is no reasonable way to tell if an NMI
643comes from the IPMI controller, so it must assume that if it gets an
644otherwise unhandled NMI, it must be from IPMI and it will panic
645immediately.
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646
647Once you open the watchdog timer, you must write a 'V' character to the
648device to close it, or the timer will not stop. This is a new semantic
649for the driver, but makes it consistent with the rest of the watchdog
650drivers in Linux.
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651
652
653Panic Timeouts
654--------------
655
656The OpenIPMI driver supports the ability to put semi-custom and custom
657events 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
659one event on a panic in a standard IPMI event format. If you enable
660the 'Generate OEM events containing the panic string' option, you will
661also get a bunch of OEM events holding the panic string.
662
663
664The 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
673See the IPMI spec for the details of the event layout. This event is
674always sent to the local management controller. It will handle routing
675the message to the right place
676
677Other OEM events have the following format:
678Record ID (bytes 0-1): Set by the SEL.
679Record type (byte 2): 0xf0 (OEM non-timestamped)
680byte 3: The slave address of the card saving the panic
681byte 4: A sequence number (starting at zero)
682The rest of the bytes (11 bytes) are the panic string. If the panic string
683is longer than 11 bytes, multiple messages will be sent with increasing
684sequence numbers.
685
686Because you cannot send OEM events using the standard interface, this
687function will attempt to find an SEL and add the events there. It
688will first query the capabilities of the local management controller.
689If it has an SEL, then they will be stored in the SEL of the local
690management controller. If not, and the local management controller is
691an event generator, the event receiver from the local management
692controller will be queried and the events sent to the SEL on that
693device. Otherwise, the events go nowhere since there is nowhere to
694send them.
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695
696
697Poweroff
698--------
699
700If the poweroff capability is selected, the IPMI driver will install
701a shutdown function into the standard poweroff function pointer. This
702is in the ipmi_poweroff module. When the system requests a powerdown,
703it will send the proper IPMI commands to do this. This is supported on
704several platforms.
705
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706There is a module parameter named "poweroff_powercycle" that may
707either be zero (do a power down) or non-zero (do a power cycle, power
708the system off, then power it on in a few seconds). Setting
709ipmi_poweroff.poweroff_control=x will do the same thing on the kernel
710command line. The parameter is also available via the proc filesystem
711in /proc/sys/dev/ipmi/poweroff_powercycle. Note that if the system
712does not support power cycling, it will always do the power off.
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714The "ifnum_to_use" parameter specifies which interface the poweroff
715code should use. The default is -1, which means to pick the first one
716registered.
717
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718Note that if you have ACPI enabled, the system will prefer using ACPI to
719power off.