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Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

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+=====================
+The Linux IPMI Driver
+=====================
+
+:Author: Corey Minyard <minyard@mvista.com> / <minyard@acm.org>
+
+The Intelligent Platform Management Interface, or IPMI, is a
+standard for controlling intelligent devices that monitor a system.
+It provides for dynamic discovery of sensors in the system and the
+ability to monitor the sensors and be informed when the sensor's
+values change or go outside certain boundaries.  It also has a
+standardized database for field-replaceable units (FRUs) and a watchdog
+timer.
+
+To use this, you need an interface to an IPMI controller in your
+system (called a Baseboard Management Controller, or BMC) and
+management software that can use the IPMI system.
+
+This document describes how to use the IPMI driver for Linux.  If you
+are not familiar with IPMI itself, see the web site at
+https://www.intel.com/design/servers/ipmi/index.htm.  IPMI is a big
+subject and I can't cover it all here!
+
+Configuration
+-------------
+
+The Linux IPMI driver is modular, which means you have to pick several
+things to have it work right depending on your hardware.  Most of
+these are available in the 'Character Devices' menu then the IPMI
+menu.
+
+No matter what, you must pick 'IPMI top-level message handler' to use
+IPMI.  What you do beyond that depends on your needs and hardware.
+
+The message handler does not provide any user-level interfaces.
+Kernel code (like the watchdog) can still use it.  If you need access
+from userland, you need to select 'Device interface for IPMI' if you
+want access through a device driver.
+
+The driver interface depends on your hardware.  If your system
+properly provides the SMBIOS info for IPMI, the driver will detect it
+and just work.  If you have a board with a standard interface (These
+will generally be either "KCS", "SMIC", or "BT", consult your hardware
+manual), choose the 'IPMI SI handler' option.  A driver also exists
+for direct I2C access to the IPMI management controller.  Some boards
+support this, but it is unknown if it will work on every board.  For
+this, choose 'IPMI SMBus handler', but be ready to try to do some
+figuring to see if it will work on your system if the SMBIOS/APCI
+information is wrong or not present.  It is fairly safe to have both
+these enabled and let the drivers auto-detect what is present.
+
+You should generally enable ACPI on your system, as systems with IPMI
+can have ACPI tables describing them.
+
+If you have a standard interface and the board manufacturer has done
+their job correctly, the IPMI controller should be automatically
+detected (via ACPI or SMBIOS tables) and should just work.  Sadly,
+many boards do not have this information.  The driver attempts
+standard defaults, but they may not work.  If you fall into this
+situation, you need to read the section below named 'The SI Driver' or
+"The SMBus Driver" on how to hand-configure your system.
+
+IPMI defines a standard watchdog timer.  You can enable this with the
+'IPMI Watchdog Timer' config option.  If you compile the driver into
+the kernel, then via a kernel command-line option you can have the
+watchdog timer start as soon as it initializes.  It also have a lot
+of other options, see the 'Watchdog' section below for more details.
+Note that you can also have the watchdog continue to run if it is
+closed (by default it is disabled on close).  Go into the 'Watchdog
+Cards' menu, enable 'Watchdog Timer Support', and enable the option
+'Disable watchdog shutdown on close'.
+
+IPMI systems can often be powered off using IPMI commands.  Select
+'IPMI Poweroff' to do this.  The driver will auto-detect if the system
+can be powered off by IPMI.  It is safe to enable this even if your
+system doesn't support this option.  This works on ATCA systems, the
+Radisys CPI1 card, and any IPMI system that supports standard chassis
+management commands.
+
+If you want the driver to put an event into the event log on a panic,
+enable the 'Generate a panic event to all BMCs on a panic' option.  If
+you want the whole panic string put into the event log using OEM
+events, enable the 'Generate OEM events containing the panic string'
+option.  You can also enable these dynamically by setting the module
+parameter named "panic_op" in the ipmi_msghandler module to "event"
+or "string".  Setting that parameter to "none" disables this function.
+
+Basic Design
+------------
+
+The Linux IPMI driver is designed to be very modular and flexible, you
+only need to take the pieces you need and you can use it in many
+different ways.  Because of that, it's broken into many chunks of
+code.  These chunks (by module name) are:
+
+ipmi_msghandler - This is the central piece of software for the IPMI
+system.  It handles all messages, message timing, and responses.  The
+IPMI users tie into this, and the IPMI physical interfaces (called
+System Management Interfaces, or SMIs) also tie in here.  This
+provides the kernelland interface for IPMI, but does not provide an
+interface for use by application processes.
+
+ipmi_devintf - This provides a userland IOCTL interface for the IPMI
+driver, each open file for this device ties in to the message handler
+as an IPMI user.
+
+ipmi_si - A driver for various system interfaces.  This supports KCS,
+SMIC, and BT interfaces.  Unless you have an SMBus interface or your
+own custom interface, you probably need to use this.
+
+ipmi_ssif - A driver for accessing BMCs on the SMBus. It uses the
+I2C kernel driver's SMBus interfaces to send and receive IPMI messages
+over the SMBus.
+
+ipmi_powernv - A driver for access BMCs on POWERNV systems.
+
+ipmi_watchdog - IPMI requires systems to have a very capable watchdog
+timer.  This driver implements the standard Linux watchdog timer
+interface on top of the IPMI message handler.
+
+ipmi_poweroff - Some systems support the ability to be turned off via
+IPMI commands.
+
+bt-bmc - This is not part of the main driver, but instead a driver for
+accessing a BMC-side interface of a BT interface.  It is used on BMCs
+running Linux to provide an interface to the host.
+
+These are all individually selectable via configuration options.
+
+Much documentation for the interface is in the include files.  The
+IPMI include files are:
+
+linux/ipmi.h - Contains the user interface and IOCTL interface for IPMI.
+
+linux/ipmi_smi.h - Contains the interface for system management interfaces
+(things that interface to IPMI controllers) to use.
+
+linux/ipmi_msgdefs.h - General definitions for base IPMI messaging.
+
+
+Addressing
+----------
+
+The IPMI addressing works much like IP addresses, you have an overlay
+to handle the different address types.  The overlay is::
+
+  struct ipmi_addr
+  {
+	int   addr_type;
+	short channel;
+	char  data[IPMI_MAX_ADDR_SIZE];
+  };
+
+The addr_type determines what the address really is.  The driver
+currently understands two different types of addresses.
+
+"System Interface" addresses are defined as::
+
+  struct ipmi_system_interface_addr
+  {
+	int   addr_type;
+	short channel;
+  };
+
+and the type is IPMI_SYSTEM_INTERFACE_ADDR_TYPE.  This is used for talking
+straight to the BMC on the current card.  The channel must be
+IPMI_BMC_CHANNEL.
+
+Messages that are destined to go out on the IPMB bus going through the
+BMC use the IPMI_IPMB_ADDR_TYPE address type.  The format is::
+
+  struct ipmi_ipmb_addr
+  {
+	int           addr_type;
+	short         channel;
+	unsigned char slave_addr;
+	unsigned char lun;
+  };
+
+The "channel" here is generally zero, but some devices support more
+than one channel, it corresponds to the channel as defined in the IPMI
+spec.
+
+There is also an IPMB direct address for a situation where the sender
+is directly on an IPMB bus and doesn't have to go through the BMC.
+You can send messages to a specific management controller (MC) on the
+IPMB using the IPMI_IPMB_DIRECT_ADDR_TYPE with the following format::
+
+  struct ipmi_ipmb_direct_addr
+  {
+	int           addr_type;
+	short         channel;
+	unsigned char slave_addr;
+	unsigned char rq_lun;
+	unsigned char rs_lun;
+  };
+
+The channel is always zero.  You can also receive commands from other
+MCs that you have registered to handle and respond to them, so you can
+use this to implement a management controller on a bus..
+
+Messages
+--------
+
+Messages are defined as::
+
+  struct ipmi_msg
+  {
+	unsigned char netfn;
+	unsigned char lun;
+	unsigned char cmd;
+	unsigned char *data;
+	int           data_len;
+  };
+
+The driver takes care of adding/stripping the header information.  The
+data portion is just the data to be send (do NOT put addressing info
+here) or the response.  Note that the completion code of a response is
+the first item in "data", it is not stripped out because that is how
+all the messages are defined in the spec (and thus makes counting the
+offsets a little easier :-).
+
+When using the IOCTL interface from userland, you must provide a block
+of data for "data", fill it, and set data_len to the length of the
+block of data, even when receiving messages.  Otherwise the driver
+will have no place to put the message.
+
+Messages coming up from the message handler in kernelland will come in
+as::
+
+  struct ipmi_recv_msg
+  {
+	struct list_head link;
+
+	/* The type of message as defined in the "Receive Types"
+           defines above. */
+	int         recv_type;
+
+	ipmi_user_t      *user;
+	struct ipmi_addr addr;
+	long             msgid;
+	struct ipmi_msg  msg;
+
+	/* Call this when done with the message.  It will presumably free
+	   the message and do any other necessary cleanup. */
+	void (*done)(struct ipmi_recv_msg *msg);
+
+	/* Place-holder for the data, don't make any assumptions about
+	   the size or existence of this, since it may change. */
+	unsigned char   msg_data[IPMI_MAX_MSG_LENGTH];
+  };
+
+You should look at the receive type and handle the message
+appropriately.
+
+
+The Upper Layer Interface (Message Handler)
+-------------------------------------------
+
+The upper layer of the interface provides the users with a consistent
+view of the IPMI interfaces.  It allows multiple SMI interfaces to be
+addressed (because some boards actually have multiple BMCs on them)
+and the user should not have to care what type of SMI is below them.
+
+
+Watching For Interfaces
+^^^^^^^^^^^^^^^^^^^^^^^
+
+When your code comes up, the IPMI driver may or may not have detected
+if IPMI devices exist.  So you might have to defer your setup until
+the device is detected, or you might be able to do it immediately.
+To handle this, and to allow for discovery, you register an SMI
+watcher with ipmi_smi_watcher_register() to iterate over interfaces
+and tell you when they come and go.
+
+
+Creating the User
+^^^^^^^^^^^^^^^^^
+
+To use the message handler, you must first create a user using
+ipmi_create_user.  The interface number specifies which SMI you want
+to connect to, and you must supply callback functions to be called
+when data comes in.  The callback function can run at interrupt level,
+so be careful using the callbacks.  This also allows to you pass in a
+piece of data, the handler_data, that will be passed back to you on
+all calls.
+
+Once you are done, call ipmi_destroy_user() to get rid of the user.
+
+From userland, opening the device automatically creates a user, and
+closing the device automatically destroys the user.
+
+
+Messaging
+^^^^^^^^^
+
+To send a message from kernel-land, the ipmi_request_settime() call does
+pretty much all message handling.  Most of the parameter are
+self-explanatory.  However, it takes a "msgid" parameter.  This is NOT
+the sequence number of messages.  It is simply a long value that is
+passed back when the response for the message is returned.  You may
+use it for anything you like.
+
+Responses come back in the function pointed to by the ipmi_recv_hndl
+field of the "handler" that you passed in to ipmi_create_user().
+Remember again, these may be running at interrupt level.  Remember to
+look at the receive type, too.
+
+From userland, you fill out an ipmi_req_t structure and use the
+IPMICTL_SEND_COMMAND ioctl.  For incoming stuff, you can use select()
+or poll() to wait for messages to come in.  However, you cannot use
+read() to get them, you must call the IPMICTL_RECEIVE_MSG with the
+ipmi_recv_t structure to actually get the message.  Remember that you
+must supply a pointer to a block of data in the msg.data field, and
+you must fill in the msg.data_len field with the size of the data.
+This gives the receiver a place to actually put the message.
+
+If the message cannot fit into the data you provide, you will get an
+EMSGSIZE error and the driver will leave the data in the receive
+queue.  If you want to get it and have it truncate the message, us
+the IPMICTL_RECEIVE_MSG_TRUNC ioctl.
+
+When you send a command (which is defined by the lowest-order bit of
+the netfn per the IPMI spec) on the IPMB bus, the driver will
+automatically assign the sequence number to the command and save the
+command.  If the response is not receive in the IPMI-specified 5
+seconds, it will generate a response automatically saying the command
+timed out.  If an unsolicited response comes in (if it was after 5
+seconds, for instance), that response will be ignored.
+
+In kernelland, after you receive a message and are done with it, you
+MUST call ipmi_free_recv_msg() on it, or you will leak messages.  Note
+that you should NEVER mess with the "done" field of a message, that is
+required to properly clean up the message.
+
+Note that when sending, there is an ipmi_request_supply_msgs() call
+that lets you supply the smi and receive message.  This is useful for
+pieces of code that need to work even if the system is out of buffers
+(the watchdog timer uses this, for instance).  You supply your own
+buffer and own free routines.  This is not recommended for normal use,
+though, since it is tricky to manage your own buffers.
+
+
+Events and Incoming Commands
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The driver takes care of polling for IPMI events and receiving
+commands (commands are messages that are not responses, they are
+commands that other things on the IPMB bus have sent you).  To receive
+these, you must register for them, they will not automatically be sent
+to you.
+
+To receive events, you must call ipmi_set_gets_events() and set the
+"val" to non-zero.  Any events that have been received by the driver
+since startup will immediately be delivered to the first user that
+registers for events.  After that, if multiple users are registered
+for events, they will all receive all events that come in.
+
+For receiving commands, you have to individually register commands you
+want to receive.  Call ipmi_register_for_cmd() and supply the netfn
+and command name for each command you want to receive.  You also
+specify a bitmask of the channels you want to receive the command from
+(or use IPMI_CHAN_ALL for all channels if you don't care).  Only one
+user may be registered for each netfn/cmd/channel, but different users
+may register for different commands, or the same command if the
+channel bitmasks do not overlap.
+
+To respond to a received command, set the response bit in the returned
+netfn, use the address from the received message, and use the same
+msgid that you got in the receive message.
+
+From userland, equivalent IOCTLs are provided to do these functions.
+
+
+The Lower Layer (SMI) Interface
+-------------------------------
+
+As mentioned before, multiple SMI interfaces may be registered to the
+message handler, each of these is assigned an interface number when
+they register with the message handler.  They are generally assigned
+in the order they register, although if an SMI unregisters and then
+another one registers, all bets are off.
+
+The ipmi_smi.h defines the interface for management interfaces, see
+that for more details.
+
+
+The SI Driver
+-------------
+
+The SI driver allows KCS, BT, and SMIC interfaces to be configured
+in the system.  It discovers interfaces through a host of different
+methods, depending on the system.
+
+You can specify up to four interfaces on the module load line and
+control some module parameters::
+
+  modprobe ipmi_si.o type=<type1>,<type2>....
+       ports=<port1>,<port2>... addrs=<addr1>,<addr2>...
+       irqs=<irq1>,<irq2>...
+       regspacings=<sp1>,<sp2>,... regsizes=<size1>,<size2>,...
+       regshifts=<shift1>,<shift2>,...
+       slave_addrs=<addr1>,<addr2>,...
+       force_kipmid=<enable1>,<enable2>,...
+       kipmid_max_busy_us=<ustime1>,<ustime2>,...
+       unload_when_empty=[0|1]
+       trydmi=[0|1] tryacpi=[0|1]
+       tryplatform=[0|1] trypci=[0|1]
+
+Each of these except try... items is a list, the first item for the
+first interface, second item for the second interface, etc.
+
+The si_type may be either "kcs", "smic", or "bt".  If you leave it blank, it
+defaults to "kcs".
+
+If you specify addrs as non-zero for an interface, the driver will
+use the memory address given as the address of the device.  This
+overrides si_ports.
+
+If you specify ports as non-zero for an interface, the driver will
+use the I/O port given as the device address.
+
+If you specify irqs as non-zero for an interface, the driver will
+attempt to use the given interrupt for the device.
+
+The other try... items disable discovery by their corresponding
+names.  These are all enabled by default, set them to zero to disable
+them.  The tryplatform disables openfirmware.
+
+The next three parameters have to do with register layout.  The
+registers used by the interfaces may not appear at successive
+locations and they may not be in 8-bit registers.  These parameters
+allow the layout of the data in the registers to be more precisely
+specified.
+
+The regspacings parameter give the number of bytes between successive
+register start addresses.  For instance, if the regspacing is set to 4
+and the start address is 0xca2, then the address for the second
+register would be 0xca6.  This defaults to 1.
+
+The regsizes parameter gives the size of a register, in bytes.  The
+data used by IPMI is 8-bits wide, but it may be inside a larger
+register.  This parameter allows the read and write type to specified.
+It may be 1, 2, 4, or 8.  The default is 1.
+
+Since the register size may be larger than 32 bits, the IPMI data may not
+be in the lower 8 bits.  The regshifts parameter give the amount to shift
+the data to get to the actual IPMI data.
+
+The slave_addrs specifies the IPMI address of the local BMC.  This is
+usually 0x20 and the driver defaults to that, but in case it's not, it
+can be specified when the driver starts up.
+
+The force_ipmid parameter forcefully enables (if set to 1) or disables
+(if set to 0) the kernel IPMI daemon.  Normally this is auto-detected
+by the driver, but systems with broken interrupts might need an enable,
+or users that don't want the daemon (don't need the performance, don't
+want the CPU hit) can disable it.
+
+If unload_when_empty is set to 1, the driver will be unloaded if it
+doesn't find any interfaces or all the interfaces fail to work.  The
+default is one.  Setting to 0 is useful with the hotmod, but is
+obviously only useful for modules.
+
+When compiled into the kernel, the parameters can be specified on the
+kernel command line as::
+
+  ipmi_si.type=<type1>,<type2>...
+       ipmi_si.ports=<port1>,<port2>... ipmi_si.addrs=<addr1>,<addr2>...
+       ipmi_si.irqs=<irq1>,<irq2>...
+       ipmi_si.regspacings=<sp1>,<sp2>,...
+       ipmi_si.regsizes=<size1>,<size2>,...
+       ipmi_si.regshifts=<shift1>,<shift2>,...
+       ipmi_si.slave_addrs=<addr1>,<addr2>,...
+       ipmi_si.force_kipmid=<enable1>,<enable2>,...
+       ipmi_si.kipmid_max_busy_us=<ustime1>,<ustime2>,...
+
+It works the same as the module parameters of the same names.
+
+If your IPMI interface does not support interrupts and is a KCS or
+SMIC interface, the IPMI driver will start a kernel thread for the
+interface to help speed things up.  This is a low-priority kernel
+thread that constantly polls the IPMI driver while an IPMI operation
+is in progress.  The force_kipmid module parameter will all the user to
+force this thread on or off.  If you force it off and don't have
+interrupts, the driver will run VERY slowly.  Don't blame me,
+these interfaces suck.
+
+Unfortunately, this thread can use a lot of CPU depending on the
+interface's performance.  This can waste a lot of CPU and cause
+various issues with detecting idle CPU and using extra power.  To
+avoid this, the kipmid_max_busy_us sets the maximum amount of time, in
+microseconds, that kipmid will spin before sleeping for a tick.  This
+value sets a balance between performance and CPU waste and needs to be
+tuned to your needs.  Maybe, someday, auto-tuning will be added, but
+that's not a simple thing and even the auto-tuning would need to be
+tuned to the user's desired performance.
+
+The driver supports a hot add and remove of interfaces.  This way,
+interfaces can be added or removed after the kernel is up and running.
+This is done using /sys/modules/ipmi_si/parameters/hotmod, which is a
+write-only parameter.  You write a string to this interface.  The string
+has the format::
+
+   <op1>[:op2[:op3...]]
+
+The "op"s are::
+
+   add|remove,kcs|bt|smic,mem|i/o,<address>[,<opt1>[,<opt2>[,...]]]
+
+You can specify more than one interface on the line.  The "opt"s are::
+
+   rsp=<regspacing>
+   rsi=<regsize>
+   rsh=<regshift>
+   irq=<irq>
+   ipmb=<ipmb slave addr>
+
+and these have the same meanings as discussed above.  Note that you
+can also use this on the kernel command line for a more compact format
+for specifying an interface.  Note that when removing an interface,
+only the first three parameters (si type, address type, and address)
+are used for the comparison.  Any options are ignored for removing.
+
+The SMBus Driver (SSIF)
+-----------------------
+
+The SMBus driver allows up to 4 SMBus devices to be configured in the
+system.  By default, the driver will only register with something it
+finds in DMI or ACPI tables.  You can change this
+at module load time (for a module) with::
+
+  modprobe ipmi_ssif.o
+	addr=<i2caddr1>[,<i2caddr2>[,...]]
+	adapter=<adapter1>[,<adapter2>[...]]
+	dbg=<flags1>,<flags2>...
+	slave_addrs=<addr1>,<addr2>,...
+	tryacpi=[0|1] trydmi=[0|1]
+	[dbg_probe=1]
+	alerts_broken
+
+The addresses are normal I2C addresses.  The adapter is the string
+name of the adapter, as shown in /sys/class/i2c-adapter/i2c-<n>/name.
+It is *NOT* i2c-<n> itself.  Also, the comparison is done ignoring
+spaces, so if the name is "This is an I2C chip" you can say
+adapter_name=ThisisanI2cchip.  This is because it's hard to pass in
+spaces in kernel parameters.
+
+The debug flags are bit flags for each BMC found, they are:
+IPMI messages: 1, driver state: 2, timing: 4, I2C probe: 8
+
+The tryxxx parameters can be used to disable detecting interfaces
+from various sources.
+
+Setting dbg_probe to 1 will enable debugging of the probing and
+detection process for BMCs on the SMBusses.
+
+The slave_addrs specifies the IPMI address of the local BMC.  This is
+usually 0x20 and the driver defaults to that, but in case it's not, it
+can be specified when the driver starts up.
+
+alerts_broken does not enable SMBus alert for SSIF. Otherwise SMBus
+alert will be enabled on supported hardware.
+
+Discovering the IPMI compliant BMC on the SMBus can cause devices on
+the I2C bus to fail. The SMBus driver writes a "Get Device ID" IPMI
+message as a block write to the I2C bus and waits for a response.
+This action can be detrimental to some I2C devices. It is highly
+recommended that the known I2C address be given to the SMBus driver in
+the smb_addr parameter unless you have DMI or ACPI data to tell the
+driver what to use.
+
+When compiled into the kernel, the addresses can be specified on the
+kernel command line as::
+
+  ipmb_ssif.addr=<i2caddr1>[,<i2caddr2>[...]]
+	ipmi_ssif.adapter=<adapter1>[,<adapter2>[...]]
+	ipmi_ssif.dbg=<flags1>[,<flags2>[...]]
+	ipmi_ssif.dbg_probe=1
+	ipmi_ssif.slave_addrs=<addr1>[,<addr2>[...]]
+	ipmi_ssif.tryacpi=[0|1] ipmi_ssif.trydmi=[0|1]
+
+These are the same options as on the module command line.
+
+The I2C driver does not support non-blocking access or polling, so
+this driver cannod to IPMI panic events, extend the watchdog at panic
+time, or other panic-related IPMI functions without special kernel
+patches and driver modifications.  You can get those at the openipmi
+web page.
+
+The driver supports a hot add and remove of interfaces through the I2C
+sysfs interface.
+
+The IPMI IPMB Driver
+--------------------
+
+This driver is for supporting a system that sits on an IPMB bus; it
+allows the interface to look like a normal IPMI interface.  Sending
+system interface addressed messages to it will cause the message to go
+to the registered BMC on the system (default at IPMI address 0x20).
+
+It also allows you to directly address other MCs on the bus using the
+ipmb direct addressing.  You can receive commands from other MCs on
+the bus and they will be handled through the normal received command
+mechanism described above.
+
+Parameters are::
+
+  ipmi_ipmb.bmcaddr=<address to use for system interface addresses messages>
+	ipmi_ipmb.retry_time_ms=<Time between retries on IPMB>
+	ipmi_ipmb.max_retries=<Number of times to retry a message>
+
+Loading the module will not result in the driver automatcially
+starting unless there is device tree information setting it up.  If
+you want to instantiate one of these by hand, do::
+
+  echo ipmi-ipmb <addr> > /sys/class/i2c-dev/i2c-<n>/device/new_device
+
+Note that the address you give here is the I2C address, not the IPMI
+address.  So if you want your MC address to be 0x60, you put 0x30
+here.  See the I2C driver info for more details.
+
+Command bridging to other IPMB busses through this interface does not
+work.  The receive message queue is not implemented, by design.  There
+is only one receive message queue on a BMC, and that is meant for the
+host drivers, not something on the IPMB bus.
+
+A BMC may have multiple IPMB busses, which bus your device sits on
+depends on how the system is wired.  You can fetch the channels with
+"ipmitool channel info <n>" where <n> is the channel, with the
+channels being 0-7 and try the IPMB channels.
+
+Other Pieces
+------------
+
+Get the detailed info related with the IPMI device
+--------------------------------------------------
+
+Some users need more detailed information about a device, like where
+the address came from or the raw base device for the IPMI interface.
+You can use the IPMI smi_watcher to catch the IPMI interfaces as they
+come or go, and to grab the information, you can use the function
+ipmi_get_smi_info(), which returns the following structure::
+
+  struct ipmi_smi_info {
+	enum ipmi_addr_src addr_src;
+	struct device *dev;
+	union {
+		struct {
+			void *acpi_handle;
+		} acpi_info;
+	} addr_info;
+  };
+
+Currently special info for only for SI_ACPI address sources is
+returned.  Others may be added as necessary.
+
+Note that the dev pointer is included in the above structure, and
+assuming ipmi_smi_get_info returns success, you must call put_device
+on the dev pointer.
+
+
+Watchdog
+--------
+
+A watchdog timer is provided that implements the Linux-standard
+watchdog timer interface.  It has three module parameters that can be
+used to control it::
+
+  modprobe ipmi_watchdog timeout=<t> pretimeout=<t> action=<action type>
+      preaction=<preaction type> preop=<preop type> start_now=x
+      nowayout=x ifnum_to_use=n panic_wdt_timeout=<t>
+
+ifnum_to_use specifies which interface the watchdog timer should use.
+The default is -1, which means to pick the first one registered.
+
+The timeout is the number of seconds to the action, and the pretimeout
+is the amount of seconds before the reset that the pre-timeout panic will
+occur (if pretimeout is zero, then pretimeout will not be enabled).  Note
+that the pretimeout is the time before the final timeout.  So if the
+timeout is 50 seconds and the pretimeout is 10 seconds, then the pretimeout
+will occur in 40 second (10 seconds before the timeout). The panic_wdt_timeout
+is the value of timeout which is set on kernel panic, in order to let actions
+such as kdump to occur during panic.
+
+The action may be "reset", "power_cycle", or "power_off", and
+specifies what to do when the timer times out, and defaults to
+"reset".
+
+The preaction may be "pre_smi" for an indication through the SMI
+interface, "pre_int" for an indication through the SMI with an
+interrupts, and "pre_nmi" for a NMI on a preaction.  This is how
+the driver is informed of the pretimeout.
+
+The preop may be set to "preop_none" for no operation on a pretimeout,
+"preop_panic" to set the preoperation to panic, or "preop_give_data"
+to provide data to read from the watchdog device when the pretimeout
+occurs.  A "pre_nmi" setting CANNOT be used with "preop_give_data"
+because you can't do data operations from an NMI.
+
+When preop is set to "preop_give_data", one byte comes ready to read
+on the device when the pretimeout occurs.  Select and fasync work on
+the device, as well.
+
+If start_now is set to 1, the watchdog timer will start running as
+soon as the driver is loaded.
+
+If nowayout is set to 1, the watchdog timer will not stop when the
+watchdog device is closed.  The default value of nowayout is true
+if the CONFIG_WATCHDOG_NOWAYOUT option is enabled, or false if not.
+
+When compiled into the kernel, the kernel command line is available
+for configuring the watchdog::
+
+  ipmi_watchdog.timeout=<t> ipmi_watchdog.pretimeout=<t>
+	ipmi_watchdog.action=<action type>
+	ipmi_watchdog.preaction=<preaction type>
+	ipmi_watchdog.preop=<preop type>
+	ipmi_watchdog.start_now=x
+	ipmi_watchdog.nowayout=x
+	ipmi_watchdog.panic_wdt_timeout=<t>
+
+The options are the same as the module parameter options.
+
+The watchdog will panic and start a 120 second reset timeout if it
+gets a pre-action.  During a panic or a reboot, the watchdog will
+start a 120 timer if it is running to make sure the reboot occurs.
+
+Note that if you use the NMI preaction for the watchdog, you MUST NOT
+use the nmi watchdog.  There is no reasonable way to tell if an NMI
+comes from the IPMI controller, so it must assume that if it gets an
+otherwise unhandled NMI, it must be from IPMI and it will panic
+immediately.
+
+Once you open the watchdog timer, you must write a 'V' character to the
+device to close it, or the timer will not stop.  This is a new semantic
+for the driver, but makes it consistent with the rest of the watchdog
+drivers in Linux.
+
+
+Panic Timeouts
+--------------
+
+The OpenIPMI driver supports the ability to put semi-custom and custom
+events in the system event log if a panic occurs.  if you enable the
+'Generate a panic event to all BMCs on a panic' option, you will get
+one event on a panic in a standard IPMI event format.  If you enable
+the 'Generate OEM events containing the panic string' option, you will
+also get a bunch of OEM events holding the panic string.
+
+
+The field settings of the events are:
+
+* Generator ID: 0x21 (kernel)
+* EvM Rev: 0x03 (this event is formatting in IPMI 1.0 format)
+* Sensor Type: 0x20 (OS critical stop sensor)
+* Sensor #: The first byte of the panic string (0 if no panic string)
+* Event Dir | Event Type: 0x6f (Assertion, sensor-specific event info)
+* Event Data 1: 0xa1 (Runtime stop in OEM bytes 2 and 3)
+* Event data 2: second byte of panic string
+* Event data 3: third byte of panic string
+
+See the IPMI spec for the details of the event layout.  This event is
+always sent to the local management controller.  It will handle routing
+the message to the right place
+
+Other OEM events have the following format:
+
+* Record ID (bytes 0-1): Set by the SEL.
+* Record type (byte 2): 0xf0 (OEM non-timestamped)
+* byte 3: The slave address of the card saving the panic
+* byte 4: A sequence number (starting at zero)
+  The rest of the bytes (11 bytes) are the panic string.  If the panic string
+  is longer than 11 bytes, multiple messages will be sent with increasing
+  sequence numbers.
+
+Because you cannot send OEM events using the standard interface, this
+function will attempt to find an SEL and add the events there.  It
+will first query the capabilities of the local management controller.
+If it has an SEL, then they will be stored in the SEL of the local
+management controller.  If not, and the local management controller is
+an event generator, the event receiver from the local management
+controller will be queried and the events sent to the SEL on that
+device.  Otherwise, the events go nowhere since there is nowhere to
+send them.
+
+
+Poweroff
+--------
+
+If the poweroff capability is selected, the IPMI driver will install
+a shutdown function into the standard poweroff function pointer.  This
+is in the ipmi_poweroff module.  When the system requests a powerdown,
+it will send the proper IPMI commands to do this.  This is supported on
+several platforms.
+
+There is a module parameter named "poweroff_powercycle" that may
+either be zero (do a power down) or non-zero (do a power cycle, power
+the system off, then power it on in a few seconds).  Setting
+ipmi_poweroff.poweroff_control=x will do the same thing on the kernel
+command line.  The parameter is also available via the proc filesystem
+in /proc/sys/dev/ipmi/poweroff_powercycle.  Note that if the system
+does not support power cycling, it will always do the power off.
+
+The "ifnum_to_use" parameter specifies which interface the poweroff
+code should use.  The default is -1, which means to pick the first one
+registered.
+
+Note that if you have ACPI enabled, the system will prefer using ACPI to
+power off.