ubi_write_fastmap(9)

💾 ubi_write_fastmap(9) — like, the Kernel API Manual girlies edition 🎀

okay so bestie, gather round, because we're diving into ubi_write_fastmap — yes it's from the Kernel API Manual section 9 (kernel internals, iykyk) and yes it does exactly what it says on the tin: it writes a fastmap. that's the whole vibe. let's get into it 💅

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✨ SYNOPSIS ✨

int ubi_write_fastmap (struct ubi_device *ubi , struct
       ubi_fastmap_layout *new_fm );

literally the whole signature, no notes, copy it exactly, don't @ me 🫶

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🌸 ARGUMENTS 🌸

• ubi — the UBI device object itself. like, the main character of this whole operation 💖
• new_fm — the fastmap that's to be written. it hasn't been written yet, it's about to be, it's giving anticipation ✨

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🦋 DESCRIPTION 🦋

so here's the tea, and it's a short one for once:

• Returns 0 on success — slay, we love a clean win 👑
• Returns < 0 — which indicates an internal error. not a vibe. something went sideways inside the kernel and you're getting a negative number instead of that sweet, sweet zero 😭

that's genuinely it. no cap, no extra lore, that's the whole description. an icon of brevity fr fr.

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🌈 SEE ALSO 🌈

bestie, the cross-references are thorough, so buckle up — this all lives in the kernel file ./drivers/mtd/ubi/fastmap.c:

• init_seen(9)
• free_seen(9)
• set_seen(9)
• self_check_seen(9)
• ubi_calc_fm_size(9)
• new_fm_vbuf(9)
• add_aeb(9)
• add_vol(9)
• assign_aeb_to_av(9)
• update_vol(9)
• process_pool_aeb(9)
• unmap_peb(9)
• scan_pool(9)
• count_fastmap_pebs(9)
• ubi_attach_fastmap(9)
• find_fm_anchor(9)
• ubi_scan_fastmap(9)
• invalidate_fastmap(9)
• return_fm_pebs(9)
• ubi_update_fastmap(9)

the way this list just keeps going — obsessed with the completeness honestly 🌸 go read them, they're all connected, it's a whole ecosystem 💜

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ngl if you get a negative return you should go poke at the internals, because < 0 means an internal error and that's your cue to investigate 🔥

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and that's the page, bestie! 🧚 this little number lives over in ./drivers/mtd/ubi, dated October 2026, and it's filed under ubi_write_fastmap(9) — that's the version-and-source sign-off, cute right? mwah 💋