STRUCT IL_AC_QOS(9)

💅 struct il_ac_qos(9) — the Kernel API Manual, but make it make sense 🎀

Okay bestie, buckle up, because we're diving into struct il_ac_qos from the Kernel API Manual (section 9, kernel-functions hive, iykyk) ✨

✨ NAME ✨

struct il_ac_qos — literally the QOS timing params for C_QOS_PARAM, and you get one of these for each of the 4 EDCA access categories inside struct il_qosparam_cmd. Four little icons, one per access category 🫶

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🌸 SYNOPSIS 🌸

struct il_ac_qos {
    __le16 cw_min;
    __le16 cw_max;
    u8 aifsn;
    u8 reserved1;
    __le16 edca_txop;
 };

No cap, that's the whole struct 💀

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🦋 Members 🦋

Here's the vibe check on every single field, and yes we're doing all of them 👑

• cw_min — the contention win start value, counted in numbers of slots. It should be a power-of-2, minus 1. The device's default is 0x0f 🍓
• cw_max — the contention win max value, also in numbers of slots. Also should be a power-of-2, minus 1. Device's default is 0x3f 🌸
• aifsn — number of slots in the Arbitration Interframe Space (that's the lil' pause before doing the random backoff timing, prior to Tx). Device default is 1 ⭐
• reserved1 — it's reserved, bestie, we don't touch it 🙈 (it's in the SYNOPSIS up there but the manpage gives it no description, so no invented lore from me, fr fr)
• edca_txop — length of the Tx opportunity, measured in uSecs. Device default is 0 🎀

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💜 Description 💜

The device will automatically increase the contention win by (2*CW) + 1 for each transmission retry. Then it uses cw_max as a bit mask, ANDed with the new CW value, to cap the CW value 💅

That's it. That's the whole behaviour. It ramps up, then it gets masked down. Main character energy from a hardware register, honestly.

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🔥 SEE ALSO 🔥

All the siblings in the kernel file ./drivers/net/wireless/intel/iwlegacy/commands.h, because this struct does not exist in a vacuum, bestie:

• struct il_cmd_header(9)
• struct il3945_tx_power(9)
• struct il3945_power_per_rate(9)
• union il4965_tx_power_dual_stream(9)
• struct tx_power_dual_stream(9)
• struct il4965_tx_power_db(9)
• struct sta_id_modify(9)
• struct il_link_qual_general_params(9)
• struct il_link_qual_agg_params(9)
• struct il_ssid_ie(9)
• struct stats_tx_power(9)
• struct il_sensitivity_cmd(9)

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Sign-off time, angel 💖 This beauty lives in ./drivers/net/wireless/intel/i... (the manpage truncates it like that, and I refuse to guess at what the rest says 🌈), and this edition is dated October 2026. Go forth and slay your contention windows, and remember: power-of-2 minus 1, always 💅✨