1# SPDX-License-Identifier: GPL-2.0-only
2menuconfig MTD_UBI
3	tristate "Enable UBI - Unsorted block images"
4	select CRC32
5	help
6	  UBI is a software layer above MTD layer which admits use of LVM-like
7	  logical volumes on top of MTD devices, hides some complexities of
8	  flash chips like wear and bad blocks and provides some other useful
9	  capabilities. Please, consult the MTD web site for more details
10	  (www.linux-mtd.infradead.org).
11
12if MTD_UBI
13
14config MTD_UBI_WL_THRESHOLD
15	int "UBI wear-leveling threshold"
16	default 4096
17	range 2 65536
18	help
19	  This parameter defines the maximum difference between the highest
20	  erase counter value and the lowest erase counter value of eraseblocks
21	  of UBI devices. When this threshold is exceeded, UBI starts performing
22	  wear leveling by means of moving data from eraseblock with low erase
23	  counter to eraseblocks with high erase counter.
24
25	  The default value should be OK for SLC NAND flashes, NOR flashes and
26	  other flashes which have eraseblock life-cycle 100000 or more.
27	  However, in case of MLC NAND flashes which typically have eraseblock
28	  life-cycle less than 10000, the threshold should be lessened (e.g.,
29	  to 128 or 256, although it does not have to be power of 2).
30
31config MTD_UBI_BEB_LIMIT
32	int "Maximum expected bad eraseblock count per 1024 eraseblocks"
33	default 20
34	range 0 768
35	help
36	  This option specifies the maximum bad physical eraseblocks UBI
37	  expects on the MTD device (per 1024 eraseblocks). If the underlying
38	  flash does not admit of bad eraseblocks (e.g. NOR flash), this value
39	  is ignored.
40
41	  NAND datasheets often specify the minimum and maximum NVM (Number of
42	  Valid Blocks) for the flashes' endurance lifetime. The maximum
43	  expected bad eraseblocks per 1024 eraseblocks then can be calculated
44	  as "1024 * (1 - MinNVB / MaxNVB)", which gives 20 for most NANDs
45	  (MaxNVB is basically the total count of eraseblocks on the chip).
46
47	  To put it differently, if this value is 20, UBI will try to reserve
48	  about 1.9% of physical eraseblocks for bad blocks handling. And that
49	  will be 1.9% of eraseblocks on the entire NAND chip, not just the MTD
50	  partition UBI attaches. This means that if you have, say, a NAND
51	  flash chip admits maximum 40 bad eraseblocks, and it is split on two
52	  MTD partitions of the same size, UBI will reserve 40 eraseblocks when
53	  attaching a partition.
54
55	  This option can be overridden by the "mtd=" UBI module parameter or
56	  by the "attach" ioctl.
57
58	  Leave the default value if unsure.
59
60config MTD_UBI_FASTMAP
61	bool "UBI Fastmap (Experimental feature)"
62	default n
63	help
64	   Important: this feature is experimental so far and the on-flash
65	   format for fastmap may change in the next kernel versions
66
67	   Fastmap is a mechanism which allows attaching an UBI device
68	   in nearly constant time. Instead of scanning the whole MTD device it
69	   only has to locate a checkpoint (called fastmap) on the device.
70	   The on-flash fastmap contains all information needed to attach
71	   the device. Using fastmap makes only sense on large devices where
72	   attaching by scanning takes long. UBI will not automatically install
73	   a fastmap on old images, but you can set the UBI module parameter
74	   fm_autoconvert to 1 if you want so. Please note that fastmap-enabled
75	   images are still usable with UBI implementations without
76	   fastmap support. On typical flash devices the whole fastmap fits
77	   into one PEB. UBI will reserve PEBs to hold two fastmaps.
78
79	   If in doubt, say "N".
80
81config MTD_UBI_GLUEBI
82	tristate "MTD devices emulation driver (gluebi)"
83	help
84	   This option enables gluebi - an additional driver which emulates MTD
85	   devices on top of UBI volumes: for each UBI volumes an MTD device is
86	   created, and all I/O to this MTD device is redirected to the UBI
87	   volume. This is handy to make MTD-oriented software (like JFFS2)
88	   work on top of UBI. Do not enable this unless you use legacy
89	   software.
90
91config MTD_UBI_BLOCK
92	bool "Read-only block devices on top of UBI volumes"
93	default n
94	depends on BLOCK
95	help
96	   This option enables read-only UBI block devices support. UBI block
97	   devices will be layered on top of UBI volumes, which means that the
98	   UBI driver will transparently handle things like bad eraseblocks and
99	   bit-flips. You can put any block-oriented file system on top of UBI
100	   volumes in read-only mode (e.g., ext4), but it is probably most
101	   practical for read-only file systems, like squashfs.
102
103	   When selected, this feature will be built in the UBI driver.
104
105	   If in doubt, say "N".
106
107config MTD_UBI_FAULT_INJECTION
108	bool "Fault injection capability of UBI device"
109	default n
110	depends on FAULT_INJECTION_DEBUG_FS
111	help
112	   This option enables fault-injection support for UBI devices for
113	   testing purposes.
114
115	   If in doubt, say "N".
116
117config MTD_UBI_NVMEM
118	tristate "UBI virtual NVMEM"
119	default n
120	depends on NVMEM
121	help
122	   This option enabled an additional driver exposing UBI volumes as NVMEM
123	   providers, intended for platforms where UBI is part of the firmware
124	   specification and used to store also e.g. MAC addresses or board-
125	   specific Wi-Fi calibration data.
126
127	   If in doubt, say "N".
128
129endif # MTD_UBI
130