Documentation: add UBI sysfs ABI docs

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Acked-by: Greg KH <greg@kroah.com>

Documentation/ABI/stable/sysfs-class-ubi

+What:		/sys/class/ubi/
+Date:		July 2006
+KernelVersion:	2.6.22
+Contact:	Artem Bityutskiy <dedekind@infradead.org>
+Description:
+		The ubi/ class sub-directory belongs to the UBI subsystem and
+		provides general UBI information, per-UBI device information
+		and per-UBI volume information.
+
+What:		/sys/class/ubi/version
+Date:		July 2006
+KernelVersion:	2.6.22
+Contact:	Artem Bityutskiy <dedekind@infradead.org>
+Description:
+		This file contains version of the latest supported UBI on-media
+		format. Currently it is 1, and there is no plan to change this.
+		However, if in the future UBI needs on-flash format changes
+		which cannot be done in a compatible manner, a new format
+		version will be added. So this is a mechanism for possible
+		future backward-compatible (but forward-incompatible)
+		improvements.
+
+What:		/sys/class/ubiX/
+Date:		July 2006
+KernelVersion:	2.6.22
+Contact:	Artem Bityutskiy <dedekind@infradead.org>
+Description:
+		The /sys/class/ubi0, /sys/class/ubi1, etc directories describe
+		UBI devices (UBI device 0, 1, etc). They contain general UBI
+		device information and per UBI volume information (each UBI
+		device may have many UBI volumes)
+
+What:		/sys/class/ubi/ubiX/avail_eraseblocks
+Date:		July 2006
+KernelVersion:	2.6.22
+Contact:	Artem Bityutskiy <dedekind@infradead.org>
+Description:
+		Amount of available logical eraseblock. For example, one may
+		create a new UBI volume which has this amount of logical
+		eraseblocks.
+
+What:		/sys/class/ubi/ubiX/bad_peb_count
+Date:		July 2006
+KernelVersion:	2.6.22
+Contact:	Artem Bityutskiy <dedekind@infradead.org>
+Description:
+		Count of bad physical eraseblocks on the underlying MTD device.
+
+What:		/sys/class/ubi/ubiX/bgt_enabled
+Date:		July 2006
+KernelVersion:	2.6.22
+Contact:	Artem Bityutskiy <dedekind@infradead.org>
+Description:
+		Contains ASCII "0\n" if the UBI background thread is disabled,
+		and ASCII "1\n" if it is enabled.
+
+What:		/sys/class/ubi/ubiX/dev
+Date:		July 2006
+KernelVersion:	2.6.22
+Contact:	Artem Bityutskiy <dedekind@infradead.org>
+Description:
+		Major and minor numbers of the character device corresponding
+		to this UBI device (in <major>:<minor> format).
+
+What:		/sys/class/ubi/ubiX/eraseblock_size
+Date:		July 2006
+KernelVersion:	2.6.22
+Contact:	Artem Bityutskiy <dedekind@infradead.org>
+Description:
+		Maximum logical eraseblock size this UBI device may provide. UBI
+		volumes may have smaller logical eraseblock size because of their
+		alignment.
+
+What:		/sys/class/ubi/ubiX/max_ec
+Date:		July 2006
+KernelVersion:	2.6.22
+Contact:	Artem Bityutskiy <dedekind@infradead.org>
+Description:
+		Maximum physical eraseblock erase counter value.
+
+What:		/sys/class/ubi/ubiX/max_vol_count
+Date:		July 2006
+KernelVersion:	2.6.22
+Contact:	Artem Bityutskiy <dedekind@infradead.org>
+Description:
+		Maximum number of volumes which this UBI device may have.
+
+What:		/sys/class/ubi/ubiX/min_io_size
+Date:		July 2006
+KernelVersion:	2.6.22
+Contact:	Artem Bityutskiy <dedekind@infradead.org>
+Description:
+		Minimum input/output unit size. All the I/O may only be done
+		in fractions of the contained number.
+
+What:		/sys/class/ubi/ubiX/mtd_num
+Date:		January 2008
+KernelVersion:	2.6.25
+Contact:	Artem Bityutskiy <dedekind@infradead.org>
+Description:
+		Number of the underlying MTD device.
+
+What:		/sys/class/ubi/ubiX/reserved_for_bad
+Date:		July 2006
+KernelVersion:	2.6.22
+Contact:	Artem Bityutskiy <dedekind@infradead.org>
+Description:
+		Number of physical eraseblocks reserved for bad block handling.
+
+What:		/sys/class/ubi/ubiX/total_eraseblocks
+Date:		July 2006
+KernelVersion:	2.6.22
+Contact:	Artem Bityutskiy <dedekind@infradead.org>
+Description:
+		Total number of good (not marked as bad) physical eraseblocks on
+		the underlying MTD device.
+
+What:		/sys/class/ubi/ubiX/volumes_count
+Date:		July 2006
+KernelVersion:	2.6.22
+Contact:	Artem Bityutskiy <dedekind@infradead.org>
+Description:
+		Count of volumes on this UBI device.
+
+What:		/sys/class/ubi/ubiX/ubiX_Y/
+Date:		July 2006
+KernelVersion:	2.6.22
+Contact:	Artem Bityutskiy <dedekind@infradead.org>
+Description:
+		The /sys/class/ubi/ubiX/ubiX_0/, /sys/class/ubi/ubiX/ubiX_1/,
+		etc directories describe UBI volumes on UBI device X (volumes
+		0, 1, etc).
+
+What:		/sys/class/ubi/ubiX/ubiX_Y/alignment
+Date:		July 2006
+KernelVersion:	2.6.22
+Contact:	Artem Bityutskiy <dedekind@infradead.org>
+Description:
+		Volume alignment - the value the logical eraseblock size of
+		this volume has to be aligned on. For example, 2048 means that
+		logical eraseblock size is multiple of 2048. In other words,
+		volume logical eraseblock size is UBI device logical eraseblock
+		size aligned to the alignment value.
+
+What:		/sys/class/ubi/ubiX/ubiX_Y/corrupted
+Date:		July 2006
+KernelVersion:	2.6.22
+Contact:	Artem Bityutskiy <dedekind@infradead.org>
+Description:
+		Contains ASCII "0\n" if the UBI volume is OK, and ASCII "1\n"
+		if it is corrupted (e.g., due to an interrupted volume update).
+
+What:		/sys/class/ubi/ubiX/ubiX_Y/data_bytes
+Date:		July 2006
+KernelVersion:	2.6.22
+Contact:	Artem Bityutskiy <dedekind@infradead.org>
+Description:
+		The amount of data this volume contains. This value makes sense
+		only for static volumes, and for dynamic volume it equivalent
+		to the total volume size in bytes.
+
+What:		/sys/class/ubi/ubiX/ubiX_Y/dev
+Date:		July 2006
+KernelVersion:	2.6.22
+Contact:	Artem Bityutskiy <dedekind@infradead.org>
+Description:
+		Major and minor numbers of the character device corresponding
+		to this UBI volume (in <major>:<minor> format).
+
+What:		/sys/class/ubi/ubiX/ubiX_Y/name
+Date:		July 2006
+KernelVersion:	2.6.22
+Contact:	Artem Bityutskiy <dedekind@infradead.org>
+Description:
+		Volume name.
+
+What:		/sys/class/ubi/ubiX/ubiX_Y/reserved_ebs
+Date:		July 2006
+KernelVersion:	2.6.22
+Contact:	Artem Bityutskiy <dedekind@infradead.org>
+Description:
+		Count of physical eraseblock reserved for this volume.
+		Equivalent to the volume size in logical eraseblocks.
+
+What:		/sys/class/ubi/ubiX/ubiX_Y/type
+Date:		July 2006
+KernelVersion:	2.6.22
+Contact:	Artem Bityutskiy <dedekind@infradead.org>
+Description:
+		Volume type. Contains ASCII "dynamic\n" for dynamic volumes and
+		"static\n" for static volumes.
+
+What:		/sys/class/ubi/ubiX/ubiX_Y/upd_marker
+Date:		July 2006
+KernelVersion:	2.6.22
+Contact:	Artem Bityutskiy <dedekind@infradead.org>
+Description:
+		Contains ASCII "0\n" if the update marker is not set for this
+		volume, and "1\n" if it is set. The update marker is set when
+		volume update starts, and cleaned when it ends. So the presence
+		of the update marker indicates that the volume is being updated
+		at the moment of the update was interrupted. The later may be
+		checked using the "corrupted" sysfs file.
+
+What:		/sys/class/ubi/ubiX/ubiX_Y/usable_eb_size
+Date:		July 2006
+KernelVersion:	2.6.22
+Contact:	Artem Bityutskiy <dedekind@infradead.org>
+Description:
+		Logical eraseblock size of this volume. Equivalent to logical
+		eraseblock size of the device aligned on the volume alignment
+		value.