ux500_swap_bits_in_byte(9)

✨ ux500_swap_bits_in_byte(9) ✨

okay bestie, so this one is from the Kernel API Manual and it's literally the cutest little bit-shuffler ever. we're talking ux500_swap_bits_in_byte — it mirrors the bits in a byte 🦋 like, full reverse-glow-up for your 8 little bits. no cap.

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🌸 SYNOPSIS 🌸

u8 ux500_swap_bits_in_byte (u8 b );

that's it. that's the whole vibe. one byte in, one byte out. 💅

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🎀 ARGUMENTS 🎀

• b — the byte that's about to get mirrored. it's the main character of this whole operation, give it a little respect 🫶

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💖 DESCRIPTION 💖

so the bits get swapped like this, and honestly the way that it works is kind of iconic. so b includes bits 0-7, right? then nibble 1 (n1) holds bits 0-3 and nibble 2 (n2) holds bits 4-7. two lil nibbles, each living their own life 😭

🧚 Nibble 1 (n1)

heads up bestie: the "old" (moved) bit gets replaced with a zero. so like, it does not survive the move, okay? it's giving farewell tour 💀

1. Move bit 6 and 7, 4 positions to the left.
2. Move bit 3 and 5, 2 positions to the left.
3. Move bit 1-4, 1 position to the left.

🧚 Nibble 2 (n2)

1. Move bit 0 and 1, 4 positions to the right.
2. Move bit 2 and 4, 2 positions to the right.
3. Move bit 3-6, 1 position to the right.

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then you combine the two nibbles into one complete, fully swapped byte. that's the finale ✨ the two halves reunite and it's beautiful. reunion episode energy fr fr 😭💖

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🦋 SEE ALSO 🦋

• Kernel file ./drivers/crypto/stm32/stm32-cryp.c
• ux500_swizzle_key(9) — the sibling, obviously 👑

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signed off with love from the ./drivers/crypto/stm32 corner of the kernel 💅 that's October 2026 energy for ya 🌈