char/ipmi: add documentation for sysfs interface

This is an attempt to document the sysfs interface for the IPMI drivers.
Descriptions were collected from v2.0 of the IPMI specification and from
code comments.
Signed-off-by: Aishwarya Pant <aishpant@gmail.com>
Signed-off-by: Corey Minyard <cminyard@mvista.com>

Documentation/ABI/testing/sysfs-devices-platform-ipmi

+What:		/sys/devices/platform/ipmi_bmc.*/firmware_revision
+Date:		Mar, 2006
+KernelVersion:	v2.6.17
+Contact:	openipmi-developer@lists.sourceforge.net
+Description:
+		(RO) The major and minor revision of the firmware.
+
+
+What:		/sys/devices/platform/ipmi_bmc.*/aux_firmware_revision
+Date:		Mar, 2006
+KernelVersion:	v2.6.17
+Contact:	openipmi-developer@lists.sourceforge.net
+Description:
+		(RO) Holds additional information about the firmware revision,
+		such as boot block or internal data structure version numbers.
+		The meanings of the numbers are specific to the vendor
+		identified by Manufacturer ID.
+
+
+What:		/sys/devices/platform/ipmi_bmc.*/revision
+Date:		Mar, 2006
+KernelVersion:	v2.6.17
+Contact:	openipmi-developer@lists.sourceforge.net
+Description:
+		(RO) Device revision. Useful for identifying if significant
+		hardware changes have been made to the implementation of the
+		management controller.
+
+
+What:		/sys/devices/platform/ipmi_bmc.*/provides_device_sdrs
+Date:		Mar, 2006
+KernelVersion:	v2.6.17
+Contact:	openipmi-developer@lists.sourceforge.net
+Description:
+		(RO) Indicates whether device provides device sensor data
+		records (1) or not (0).
+
+
+What:		/sys/devices/platform/ipmi_bmc.*/device_id
+Date:		Mar, 2006
+KernelVersion:	v2.6.17
+Contact:	openipmi-developer@lists.sourceforge.net
+Description:
+		(RO) Device id is specified by the manufacturer identified by
+		the Manufacturer ID field. This field allows controller specific
+		software to identify the unique application command, OEM
+		fields, and functionality that are provided by the controller
+
+
+What:		/sys/devices/platform/ipmi_bmc.*/additional_device_support
+Date:		Mar, 2006
+KernelVersion:	v2.6.17
+Contact:	openipmi-developer@lists.sourceforge.net
+Description:
+		(RO) Lists the IPMI ‘logical device’ commands and functions
+		that the controller supports that are in addition to the
+		mandatory IPM and Application commands.
+
+
+What:		/sys/devices/platform/ipmi_bmc.*/ipmi_version
+Date:		Mar, 2006
+KernelVersion:	v2.6.17
+Contact:	openipmi-developer@lists.sourceforge.net
+Description:
+		(RO) Displays the IPMI Command Specification Version.
+
+
+What:		/sys/devices/platform/ipmi_bmc.*/manufacturer_id
+Date:		Mar, 2006
+KernelVersion:	v2.6.17
+Contact:	openipmi-developer@lists.sourceforge.net
+Description:
+		(RO) Identifies the manufacturer responsible for the
+		specification of functionality of the vendor (OEM)-specific
+		commands, codes, and interfaces used in the controller.
+
+
+What:		/sys/devices/platform/ipmi_bmc.*/product_id
+Date:		Mar, 2006
+KernelVersion:	v2.6.17
+Contact:	openipmi-developer@lists.sourceforge.net
+Description:
+		(RO) Displays a number that identifies a particular system,
+		module, add-in card, or board set. The number is specified
+		according to the manufacturer given by Manufacturer ID.
+
+For detailed definitions of the above attributes, refer to section 20.1 'Get
+Device ID Command' of the IPMI specification v2.0.
+
+
+What:		/sys/devices/platform/ipmi_bmc.*/guid
+Date:		Mar, 2006
+KernelVersion:	v2.6.17
+Contact:	openipmi-developer@lists.sourceforge.net
+Description:
+		(RO) A GUID (Globally Unique ID), also referred to as a UUID
+		(Universally Unique Identifier), for the management controller,
+		as described in section 20.8 'Get Device GUID Command' of the
+		IPMI specification v2.0.
+
+
+What:		/sys/devices/platform/ipmi_si.*/type
+Date:		Sep, 2017
+KernelVersion:	v4.15
+Contact:	openipmi-developer@lists.sourceforge.net
+Description:
+		(RO) The device interface for IPMI "kcs", "smic", "bt" or
+		"invalid"
+
+What:		/sys/devices/platform/ipmi_si.*/idles
+What:		/sys/devices/platform/ipmi_si.*/watchdog_pretimeouts
+What:		/sys/devices/platform/ipmi_si.*/complete_transactions
+What:		/sys/devices/platform/ipmi_si.*/events
+What:		/sys/devices/platform/ipmi_si.*/interrupts
+What:		/sys/devices/platform/ipmi_si.*/hosed_count
+What:		/sys/devices/platform/ipmi_si.*/long_timeouts
+What:		/sys/devices/platform/ipmi_si.*/flag_fetches
+What:		/sys/devices/platform/ipmi_si.*/attentions
+What:		/sys/devices/platform/ipmi_si.*/incoming_messages
+What:		/sys/devices/platform/ipmi_si.*/short_timeouts
+Date:		Sep, 2017
+KernelVersion:	v4.15
+Contact:	openipmi-developer@lists.sourceforge.net
+Description:
+
+		idles:			(RO) Number of times the interface was
+					idle while being polled.
+
+		watchdog_pretimeouts:	(RO) Number of watchdog pretimeouts.
+
+		complete_transactions:	(RO) Number of completed messages.
+
+		events:			(RO) Number of IPMI events received from
+					the hardware.
+
+		interrupts:		(RO) Number of interrupts the driver
+					handled.
+
+		hosed_count:		(RO) Number of times the hardware didn't
+					follow the state machine.
+
+		long_timeouts:		(RO) Number of times the driver
+					requested a timer while nothing was in
+					progress.
+
+		flag_fetches:		(RO) Number of times the driver
+					requested flags from the hardware.
+
+		attentions:		(RO) Number of time the driver got an
+					ATTN from the hardware.
+
+		incoming_messages:	(RO) Number of asynchronous messages
+					received.
+
+		short_timeouts:		(RO) Number of times the driver
+					requested a timer while an operation was
+					in progress.
+
+
+What:		/sys/devices/platform/ipmi_si.*/interrupts_enabled
+Date:		Sep, 2017
+KernelVersion:	v4.15
+Contact:	openipmi-developer@lists.sourceforge.net
+Description:
+		(RO) Indicates whether interrupts are enabled or not. The driver
+		disables interrupts when it gets into a situation where it
+		cannot handle messages due to lack of memory. Once that
+		situation clears up, it will re-enable interrupts.
+
+
+What:		/sys/devices/platform/ipmi_si.*/params
+Date:		Sep, 2017
+KernelVersion:	v4.15
+Contact:	openipmi-developer@lists.sourceforge.net
+Description:
+		[to be documented]
+
+
+What:		/sys/devices/platform/dmi-ipmi-ssif.*/type
+Date:		Sep, 2017
+KernelVersion:	v4.15
+Contact:	openipmi-developer@lists.sourceforge.net
+Description:
+		(RO) Shows the IMPI device interface type - "ssif" here.
+
+
+What:		/sys/devices/platform/dmi-ipmi-ssif.*/hosed
+What:		/sys/devices/platform/dmi-ipmi-ssif.*/alerts
+What:		/sys/devices/platform/dmi-ipmi-ssif.*/sent_messages
+What:		/sys/devices/platform/dmi-ipmi-ssif.*/sent_messages_parts
+What:		/sys/devices/platform/dmi-ipmi-ssif.*/received_messages
+What:		/sys/devices/platform/dmi-ipmi-ssif.*/received_message_parts
+What:		/sys/devices/platform/dmi-ipmi-ssif.*/events
+What:		/sys/devices/platform/dmi-ipmi-ssif.*/watchdog_pretimeouts
+What:		/sys/devices/platform/dmi-ipmi-ssif.*/flag_fetches
+What:		/sys/devices/platform/dmi-ipmi-ssif.*/send_retries
+What:		/sys/devices/platform/dmi-ipmi-ssif.*/receive_retries
+What:		/sys/devices/platform/dmi-ipmi-ssif.*/send_errors
+What:		/sys/devices/platform/dmi-ipmi-ssif.*/receive_errors
+Date:		Sep, 2017
+KernelVersion:	v4.15
+Contact:	openipmi-developer@lists.sourceforge.net
+Description:
+		hosed:			(RO) Number of times the hardware didn't
+					follow the state machine.
+
+		alerts:			(RO) Number of alerts received.
+
+		sent_messages:		(RO) Number of total messages sent.
+
+		sent_message_parts:	(RO) Number of message parts sent.
+					Messages may be broken into parts if
+					they are long.
+
+		receieved_messages:	(RO) Number of message responses
+					received.
+
+		received_message_parts: (RO) Number of message fragments
+					received.
+
+		events:			(RO) Number of received events.
+
+		watchdog_pretimeouts:	(RO) Number of watchdog pretimeouts.
+
+		flag_fetches:		(RO) Number of times a flag fetch was
+					requested.
+
+		send_retries:		(RO) Number of time a message was
+					retried.
+
+		receive_retries:	(RO) Number of times the receive of a
+					message was retried.
+
+		send_errors:		(RO) Number of times the send of a
+					message failed.
+
+		receive_errors:		(RO) Number of errors in receiving
+					messages.