[deliverable/linux.git] / drivers / mtd / ubi / Kconfig

menuconfig MTD_UBI
	tristate "Enable UBI - Unsorted block images"
	select CRC32
	help
	  UBI is a software layer above MTD layer which admits of LVM-like
	  logical volumes on top of MTD devices, hides some complexities of
	  flash chips like wear and bad blocks and provides some other useful
	  capabilities. Please, consult the MTD web site for more details
	  (www.linux-mtd.infradead.org).

if MTD_UBI

config MTD_UBI_WL_THRESHOLD
	int "UBI wear-leveling threshold"
	default 4096
	range 2 65536
	help
	  This parameter defines the maximum difference between the highest
	  erase counter value and the lowest erase counter value of eraseblocks
	  of UBI devices. When this threshold is exceeded, UBI starts performing
	  wear leveling by means of moving data from eraseblock with low erase
	  counter to eraseblocks with high erase counter.

	  The default value should be OK for SLC NAND flashes, NOR flashes and
	  other flashes which have eraseblock life-cycle 100000 or more.
	  However, in case of MLC NAND flashes which typically have eraseblock
	  life-cycle less than 10000, the threshold should be lessened (e.g.,
	  to 128 or 256, although it does not have to be power of 2).

config MTD_UBI_BEB_LIMIT
	int "Maximum expected bad eraseblock count per 1024 eraseblocks"
	default 20
	range 0 768
	help
	  This option specifies the maximum bad physical eraseblocks UBI
	  expects on the MTD device (per 1024 eraseblocks). If the underlying
	  flash does not admit of bad eraseblocks (e.g. NOR flash), this value
	  is ignored.

	  NAND datasheets often specify the minimum and maximum NVM (Number of
	  Valid Blocks) for the flashes' endurance lifetime. The maximum
	  expected bad eraseblocks per 1024 eraseblocks then can be calculated
	  as "1024 * (1 - MinNVB / MaxNVB)", which gives 20 for most NANDs
	  (MaxNVB is basically the total count of eraseblocks on the chip).

	  To put it differently, if this value is 20, UBI will try to reserve
	  about 1.9% of physical eraseblocks for bad blocks handling. And that
	  will be 1.9% of eraseblocks on the entire NAND chip, not just the MTD
	  partition UBI attaches. This means that if you have, say, a NAND
	  flash chip admits maximum 40 bad eraseblocks, and it is split on two
	  MTD partitions of the same size, UBI will reserve 40 eraseblocks when
	  attaching a partition.

	  This option can be overridden by the "mtd=" UBI module parameter or
	  by the "attach" ioctl.

	  Leave the default value if unsure.

config MTD_UBI_FASTMAP
	bool "UBI Fastmap (Experimental feature)"
	default n
	help
	   Important: this feature is experimental so far and the on-flash
	   format for fastmap may change in the next kernel versions

	   Fastmap is a mechanism which allows attaching an UBI device
	   in nearly constant time. Instead of scanning the whole MTD device it
	   only has to locate a checkpoint (called fastmap) on the device.
	   The on-flash fastmap contains all information needed to attach
	   the device. Using fastmap makes only sense on large devices where
	   attaching by scanning takes long. UBI will not automatically install
	   a fastmap on old images, but you can set the UBI module parameter
	   fm_autoconvert to 1 if you want so. Please note that fastmap-enabled
	   images are still usable with UBI implementations without
	   fastmap support. On typical flash devices the whole fastmap fits
	   into one PEB. UBI will reserve PEBs to hold two fastmaps.

	   If in doubt, say "N".

config MTD_UBI_GLUEBI
	tristate "MTD devices emulation driver (gluebi)"
	help
	   This option enables gluebi - an additional driver which emulates MTD
	   devices on top of UBI volumes: for each UBI volumes an MTD device is
	   created, and all I/O to this MTD device is redirected to the UBI
	   volume. This is handy to make MTD-oriented software (like JFFS2)
	   work on top of UBI. Do not enable this unless you use legacy
	   software.

config MTD_UBI_BLOCK
	bool "Read-only block devices on top of UBI volumes"
	default n
	depends on BLOCK
	help
	   This option enables read-only UBI block devices support. UBI block
	   devices will be layered on top of UBI volumes, which means that the
	   UBI driver will transparently handle things like bad eraseblocks and
	   bit-flips. You can put any block-oriented file system on top of UBI
	   volumes in read-only mode (e.g., ext4), but it is probably most
	   practical for read-only file systems, like squashfs.

	   When selected, this feature will be built in the UBI driver.

	   If in doubt, say "N".

endif # MTD_UBI
Commit	Line	Data
1dd78632 HS	1	menuconfig MTD_UBI
1dd78632 HS	2	tristate "Enable UBI - Unsorted block images"
801c135c AB	3	select CRC32
	4	help
	5	UBI is a software layer above MTD layer which admits of LVM-like
	6	logical volumes on top of MTD devices, hides some complexities of
	7	flash chips like wear and bad blocks and provides some other useful
	8	capabilities. Please, consult the MTD web site for more details
	9	(www.linux-mtd.infradead.org).
	10
1dd78632 HS	11	if MTD_UBI
1dd78632 HS	12
801c135c AB	13	config MTD_UBI_WL_THRESHOLD
	14	int "UBI wear-leveling threshold"
	15	default 4096
	16	range 2 65536
801c135c AB	17	help
	18	This parameter defines the maximum difference between the highest
	19	erase counter value and the lowest erase counter value of eraseblocks
	20	of UBI devices. When this threshold is exceeded, UBI starts performing
	21	wear leveling by means of moving data from eraseblock with low erase
6e0c84e3 AB	22	counter to eraseblocks with high erase counter.
	23
	24	The default value should be OK for SLC NAND flashes, NOR flashes and
	25	other flashes which have eraseblock life-cycle 100000 or more.
	26	However, in case of MLC NAND flashes which typically have eraseblock
3f502622	27	life-cycle less than 10000, the threshold should be lessened (e.g.,
6e0c84e3	28	to 128 or 256, although it does not have to be power of 2).
801c135c	29
8beeb3bb	30	config MTD_UBI_BEB_LIMIT
ba4087e9 RG	31	int "Maximum expected bad eraseblock count per 1024 eraseblocks"
	32	default 20
	33	range 0 768
8beeb3bb SL	34	help
8beeb3bb SL	35	This option specifies the maximum bad physical eraseblocks UBI
ba4087e9 RG	36	expects on the MTD device (per 1024 eraseblocks). If the underlying
	37	flash does not admit of bad eraseblocks (e.g. NOR flash), this value
	38	is ignored.
	39
	40	NAND datasheets often specify the minimum and maximum NVM (Number of
	41	Valid Blocks) for the flashes' endurance lifetime. The maximum
	42	expected bad eraseblocks per 1024 eraseblocks then can be calculated
	43	as "1024 * (1 - MinNVB / MaxNVB)", which gives 20 for most NANDs
	44	(MaxNVB is basically the total count of eraseblocks on the chip).
	45
	46	To put it differently, if this value is 20, UBI will try to reserve
	47	about 1.9% of physical eraseblocks for bad blocks handling. And that
	48	will be 1.9% of eraseblocks on the entire NAND chip, not just the MTD
	49	partition UBI attaches. This means that if you have, say, a NAND
	50	flash chip admits maximum 40 bad eraseblocks, and it is split on two
	51	MTD partitions of the same size, UBI will reserve 40 eraseblocks when
	52	attaching a partition.
	53
db7e21c2 RG	54	This option can be overridden by the "mtd=" UBI module parameter or
db7e21c2 RG	55	by the "attach" ioctl.
edac493d	56
8beeb3bb	57	Leave the default value if unsure.
801c135c	58
76ac66e4 RW	59	config MTD_UBI_FASTMAP
	60	bool "UBI Fastmap (Experimental feature)"
	61	default n
	62	help
	63	Important: this feature is experimental so far and the on-flash
	64	format for fastmap may change in the next kernel versions
	65
	66	Fastmap is a mechanism which allows attaching an UBI device
	67	in nearly constant time. Instead of scanning the whole MTD device it
	68	only has to locate a checkpoint (called fastmap) on the device.
	69	The on-flash fastmap contains all information needed to attach
	70	the device. Using fastmap makes only sense on large devices where
	71	attaching by scanning takes long. UBI will not automatically install
	72	a fastmap on old images, but you can set the UBI module parameter
	73	fm_autoconvert to 1 if you want so. Please note that fastmap-enabled
	74	images are still usable with UBI implementations without
	75	fastmap support. On typical flash devices the whole fastmap fits
	76	into one PEB. UBI will reserve PEBs to hold two fastmaps.
	77
	78	If in doubt, say "N".
	79
801c135c	80	config MTD_UBI_GLUEBI
2ba3d76a	81	tristate "MTD devices emulation driver (gluebi)"
801c135c	82	help
2ba3d76a DP	83	This option enables gluebi - an additional driver which emulates MTD
	84	devices on top of UBI volumes: for each UBI volumes an MTD device is
	85	created, and all I/O to this MTD device is redirected to the UBI
	86	volume. This is handy to make MTD-oriented software (like JFFS2)
	87	work on top of UBI. Do not enable this unless you use legacy
	88	software.
801c135c	89
9d54c8a3 EG	90	config MTD_UBI_BLOCK
	91	bool "Read-only block devices on top of UBI volumes"
	92	default n
22d3ee5c	93	depends on BLOCK
9d54c8a3 EG	94	help
	95	This option enables read-only UBI block devices support. UBI block
	96	devices will be layered on top of UBI volumes, which means that the
	97	UBI driver will transparently handle things like bad eraseblocks and
	98	bit-flips. You can put any block-oriented file system on top of UBI
	99	volumes in read-only mode (e.g., ext4), but it is probably most
	100	practical for read-only file systems, like squashfs.
	101
	102	When selected, this feature will be built in the UBI driver.
	103
	104	If in doubt, say "N".
	105
1dd78632	106	endif # MTD_UBI