STRUCT UBI_FM_SB(9)

💾 struct ubi_fm_sb(9) — UBI fastmap super block 💾

okay bestie, welcome to the Kernel API Manual ✨ this one's a struct, not a program, so no flags to memorise — it's literally just a lil' layout blueprint. Think of it as the cover page of a very important notebook 📓💅

---

🌸 NAME 🌸

struct ubi_fm_sb — the UBI fastmap super block. that's it, that's the name, no notes 🫶

---

🦋 SYNOPSIS 🦋

here's the whole vibe, copy-pasted with love (and zero edits, because we do not mess with literal code around here 😤):

struct ubi_fm_sb {
    __be32 magic;
    __u8 version;
    __u8 padding1[3];
    __be32 data_crc;
    __be32 used_blocks;
    __be32 block_loc[UBI_FM_MAX_BLOCKS];
    __be32 block_ec[UBI_FM_MAX_BLOCKS];
    __be64 sqnum;
    __u8 padding2[32];
 };

like, look at all those fields. so structured. so organised. main character energy fr fr 👑

---

🎀 Members 🎀

okay so let's go field by field, no skipping, we don't do that here 💖

• magic — the fastmap super block magic number, and yes it's literally called UBI_FM_SB_MAGIC ✨ iconic name, no notes.
• version — the format version of this fastmap. so you know which era of fastmap you're dealing with 🕰️
• data_crc — a CRC check over the fastmap data. gotta make sure nothing got scrambled on the way, y'know? 🔍
• used_blocks — the number of PEBs this fastmap is using. count 'em, bestie 🔢
• block_loc — an array holding the location of all the PEBs of the fastmap. it's giving "map of the map" energy 🗺️
• block_ec — the erase counter for each used PEB. every single one gets its own little counter, obsessed 💅
• sqnum — the highest sequence number value at the time the fastmap was taken. peak "at the time while taking" behaviour ⏱️

little side note: padding1[3] and padding2[32] are sitting right there in the struct, but the man page doesn't say a single word about them, so I'm not gonna start making stuff up 🙈 they're just there, living their best life.

---

🌈 SEE ALSO 🌈

go read the neighbors, they're all in one file together like one big happy kernel family 🫶

• Kernel file ./drivers/mtd/ubi/ubi-media.h
• struct ubi_ec_hdr(9)
• struct ubi_vid_hdr(9)
• struct ubi_vtbl_record(9)
• struct ubi_fm_hdr(9)
• struct ubi_fm_scan_pool(9)
• struct ubi_fm_ec(9)
• struct ubi_fm_volhdr(9)
• struct ubi_fm_eba(9)

---

and that's the whole page, bestie, you ate that 🍓✨ this lil' rewrite came straight out of ./drivers/mtd/ubi and it's dated October 2026 — so yeah, mark your calendar, this is the version you're getting 💜🎀 no cap, go forth and read structs 💅