print_rsvd_warning(9)

💅 print_rsvd_warning(9) — Kernel API Manual, but make it make sense 🎀

okay bestie, so you know how manpages are like, technically correct but also deeply unreadable? yeah. this is that page, but with ✨personality✨. it's print_rsvd_warning from the Kernel API Manual, and honestly it's a little cutie pie of a function once you get past the vibes.

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🌸 NAME 🌸

print_rsvd_warning — the function that warns you when you don't have enough reserved PEBs. that's it, that's the whole job, and it does it beautifully 🫶

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✨ SYNOPSIS ✨

void print_rsvd_warning (struct ubi_device *ubi , struct ubi_attach_info
*ai );

like, look at her. void, two struct pointers, no return value. lowkey iconic. 💅

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🦋 ARGUMENTS 🦋

• ubi — the UBI device description object. your main character, fr. 👑
• ai — the UBI attach info object. the supporting cast, and honestly kind of essential. 💖

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💜 DESCRIPTION 💜

okay so here's the tea ☕: this is a helper function for ubi_eba_init, and it gets called when UBI literally cannot reserve enough PEBs for bad block handling. sadgirl moment 😭. but it doesn't just scream into the void — no ma'am — this function makes a decision about whether we actually have to print a warning or not. it's giving thoughtfulness. it's giving consideration. the algorithm goes like this:

• if this is a new UBI image, then just print the warning. straightforward. no notes. 🔥
• if this is a UBI image that's already been used for some time, print a warning only if we can reserve less than 10% of the expected amount of the reserved PEB. yes, that's a real number, yes you need to remember it. 🍓

and the idea behind all of this — the lore, if you will — is that when UBI is used, PEBs become bad. that's just life, that's just entropy, we don't panic. and the reserved pool of PEBs becomes smaller, which is completely normal, and we do not want to scare users with a warning every single time they attach the MTD device. imagine getting yelled at every attach. rude. 🙈 this was an actual issue reported by real users, so like, we listened. slay.

ngl the whole design here is just "don't be dramatic at people for normal wear and tear," and honestly? more software should be like this. 💀

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🌈 SEE ALSO 🌈

the whole extended friend group — go say hi, they're all in the kernel file ./drivers/mtd/ubi/eba.c:

• struct ubi_eba_entry(9)
• struct ubi_eba_table(9)
• ubi_next_sqnum(9)
• ubi_get_compat(9)
• ubi_eba_get_ldesc(9)
• ubi_eba_create_table(9)
• ubi_eba_destroy_table(9)
• ubi_eba_copy_table(9)
• ubi_eba_replace_table(9)
• ltree_lookup(9)
• ltree_add_entry(9)
• leb_read_lock(9)
• leb_read_unlock(9)
• leb_write_lock(9)
• leb_write_trylock(9)
• leb_write_unlock(9)
• ubi_eba_is_mapped(9)
• ubi_eba_unmap_leb(9)
• check_mapping(9)
• ubi_eba_read_leb(9)
• ubi_eba_read_leb_sg(9)
• try_recover_peb(9)
• recover_peb(9)
• try_write_vid_and_data(9)
• ubi_eba_write_leb(9)
• ubi_eba_write_leb_st(9)
• is_error_sane(9)
• ubi_eba_copy_leb(9)
• self_check_eba(9)
• ubi_eba_init(9)

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okay that's the whole page, you ate that 💅✨ this masterpiece lives in ./drivers/mtd/ubi, it's dated October 2026, and yes, the page name is still print_rsvd_warning(9) in case you forgot already 🎀 bye bestie, go reserve some PEBs responsibly 🦋💖