CONFIG_MTD_UBI_BEB_LIMIT: Maximum expected bad eraseblock count per 1024 eraseblocks

General informations

The Linux kernel configuration item CONFIG_MTD_UBI_BEB_LIMIT:

• prompt: Maximum expected bad eraseblock count per 1024 eraseblocks
• type: int
• depends on: (none)
• defined in drivers/mtd/ubi/Kconfig
• found in Linux kernels: 3.7–3.19, 4.0–4.20, 5.0–5.19, 6.0–6.8, 6.9-rc+HEAD

Help text

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.

Hardware

LKDDb

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• (none)

Sources

This page is automaticly generated with free (libre, open) software lkddb(see lkddb-sources).

The data is retrived from:

• Linux kernel
• Linux Kernel Driver DataBase (LKDDb)

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