ethnl_parse_bitset(9)

💅 ethnl_parse_bitset — Kernel API Manual, bestie edition

okay so this is ethnl_parse_bitset from the kernel API manual and it is literally the function that does the math homework for you 🧮✨ It computes the effective value and mask from a bitset nest. Iconic. No cap.

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✨ SYNOPSIS ✨

int ethnl_parse_bitset (unsigned long *val , unsigned long *mask ,
       unsigned int nbits , const struct nlattr *attr , ethnl_string_array_t
       names , struct netlink_ext_ack *extack );

that's the whole vibe right there 🫶 five args, one int return, zero drama.

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🎀 ARGUMENTS 🎀

• val — an unsigned long based bitmap, and it's where the value goes. like, the output value slot 💖
• mask — also an unsigned long based bitmap, and it's where the mask goes. twin of val, bestie behavior fr fr.
• nbits — the size of the val and mask bitmaps. so like, how many bits each one holds 🦋
• attr — the nest attribute you're parsing and applying. this is the actual data being decoded ✨
• names — array of bit names. may be null for compact format — yes, NULL is allowed, she's flexible 💅
• extack — extack, used for error reporting. the "what went wrong" messenger 📢

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🌸 DESCRIPTION 🌸

so here's the tea ☕: you hand over nbits-size-long bitmaps for val and mask, and the whole point is this —

x = (val & mask) | (x & ~mask)

the way that this formula would modify any nbits sized bitmap x the exact same way ethnl_update_bitset with the same bitset attribute would. like, identical outcome, no divergence, periodt. 👑

basically: precompute the effective value + mask once, then you can slam that update formula onto any x and it's giving correctly-updated bitmap every time 🔥

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⭐ RETURN ⭐

• negative error code on failure 😭
• 0 on success 🎉

yes it's that simple, and yes you should still check it. literally always check your returns, bestie, i'm begging 🙈

ngl this is a "check the return value or perish" situation. 0 = slay. < 0 = something went sideways.

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🦋 SEE ALSO 🦋

• the kernel file ./net/ethtool/bitset.c — the mothership 💜
• ethnl_bitmap32_clear(9)
• ethnl_bitmap32_not_zero(9)
• ethnl_bitmap32_update(9)
• ethnl_bitset32_size(9)
• ethnl_put_bitset32(9)
• ethnl_bitset_is_compact(9)
• ethnl_name_to_idx(9)
• ethnl_bitmap32_equal(9)
• ethnl_update_bitset32(9)

that's the whole friend group, go say hi 👋💖

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okay that's the whole page!! tysm for reading, mwah 🫶 from ./net/ethtool, October 2026 — the Kernel API Manual era, and honestly? we ate. 👑✨🎀