bitmap_write(9)

💖 bitmap_write(9) — the bitmap_write girlies' guide 💖

okay so bestie, this page is from the Kernel API Manual, section 9, and it's all about bitmap_write — the little function that tucks an n-bit value into a bitmap and honestly? she's iconic for it. 🌸

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✨ SYNOPSIS ✨

void bitmap_write (unsigned long *map , unsigned long value , unsigned
long start , unsigned long nbits );

like, that's the whole thing. no cap, that's it. 💅

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🎀 ARGUMENTS 🎀

• map — address to the bitmap memory region. this is the vibe, the venue, the place where the bits actually live 🗺️
• value — value to write, clamped to nbits. ok so important: she gets clamped to nbits, so don't come crying if your extra bits didn't make the cut 💀
• start — bit offset of the n-bit value. i.e. where in the bitmap your little value starts living ✨
• nbits — size of value in bits, nonzero, up to BITS_PER_LONG. so like… nonzero. and not bigger than BITS_PER_LONG. noted, bestie 🔥

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🦋 DESCRIPTION 🦋

bitmap_write behaves as-if implemented as nbits calls of __assign_bit — the way that she just calls it over and over, one bit at a time, obsessed fr fr. and bits beyond nbits are ignored:

for (bit = 0; bit < nbits; bit++) __assign_bit(start + bit, bitmap, val
& BIT(bit));

like literally the whole personality is that loop 😭

heads up bestie: for nbits == 0 and nbits > BITS_PER_LONG, no writes are performed. not a single write. zero. she simply does not show up 🙈

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👑 SEE ALSO 👑

go read these too, iykyk, they're all part of the same friend group 💜

• Kernel file ./include/linux/bitmap.h bitmap overview(9)
• bitmap bitops(9)
• declare bitmap(9)
• bitmap_find_next_zero_area(9)
• bitmap_or_equal(9)
• bitmap_weight_from(9)
• bitmap_scatter(9)
• bitmap_gather(9)
• bitmap_release_region(9)
• bitmap_allocate_region(9)
• bitmap_find_free_region(9)
• BITMAP_FROM_U64(9)
• bitmap_from_u64(9)
• bitmap_read(9)

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🌈 ok that's the page!! source is the kernel file ./include/linux, dated October 2026, from the Kernel API Manual — mwah, slay, go write some bits bestie 🫶💖✨