STRUCT TB_MARGINING(9)

✨ struct tb_margining(9) ✨

okay so bestie, welcome to the lane margining glow-up 💅 this is a page straight out of the Kernel API Manual, and it's all about struct tb_margining — the lane margining support struct. yes, margining. no, not the cocktail kind. 🍓

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🎀 NAME 🎀

struct tb_margining — lane margining support 💖 literally the whole personality of this struct.

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🌸 SYNOPSIS 🌸

here's the struct in all its main-character glory, copy-pasted exactly because we do not mess with code:

struct tb_margining {
    struct tb_port *port;
    enum usb4_sb_target target;
    u8 index;
    struct device *dev;
    unsigned int gen;
    bool asym_rx;
    u32 caps[3];
    u32 results[3];
    enum usb4_margining_lane lanes;
    unsigned int min_ber_level;
    unsigned int max_ber_level;
    unsigned int ber_level;
    unsigned int voltage_steps;
    unsigned int max_voltage_offset;
    unsigned int voltage_steps_optional_range;
    unsigned int max_voltage_offset_optional_range;
    unsigned int time_steps;
    unsigned int max_time_offset;
    unsigned int voltage_time_offset;
    unsigned int dwell_time;
    enum usb4_margin_sw_error_counter error_counter;
    bool optional_voltage_offset_range;
    bool software;
    bool time;
    bool right_high;
    bool upper_eye;
};

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🦋 Members 🦋

okay now the field-by-field tour, no cap 🫶

• port — the USB4 port that the margining operations actually run through. it's giving "the doorway you walk through." 🚪
• target — the sideband target. iykyk.
• index — the retimer index, but only if taget is USB4_SB_TARGET_RETIMER. and yeah, "taget" is spelled like that in the original, not me being chaotic 🙈 keep the source's spelling, it's iconic in its own way.
• dev — pointer to the device that is the target (so: the USB4 port or the retimer). pointing at your fave ✨
• gen — link generation.
• asym_rx — true% if the port supports an asymmetric link with 3 Rx. (yes, true%. that's literally what it says. the percent sign said slay and stayed 💀)
• caps — port lane margining capabilities.
• results — the last lane margining results. receipts! 🧾
• lanes — 0, 1 or 7 (all). that's the whole menu, bestie.
• min_ber_level — minimum supported BER level contour value.
• max_ber_level — maximum supported BER level contour value.
• ber_level — the current BER level contour value.
• voltage_steps — number of mandatory voltage steps.
• max_voltage_offset — maximum mandatory voltage offset (in mV).
• voltage_steps_optional_range — number of voltage steps for the optional range.
• max_voltage_offset_optional_range — maximum voltage offset for the optional range (in mV). (with a period, because she's thorough 💅)
• time_steps — number of time margin steps.
• max_time_offset — maximum time margin offset (in mUI).
• voltage_time_offset — offset for voltage / time for software margining.
• dwell_time — dwell time for software margining (in ms).
• error_counter — error counter operation for software margining.
• optional_voltage_offset_range — enable the optional extended voltage range. go off, extended range 👑
• software — true if software margining is used instead of hardware.
• time — true if time margining is used instead of voltage.
• right_high — false if a left/low margin test is performed, true if right/high.
• upper_eye — false if the lower PAM3 eye is used, true if the upper eye is used. 👁️ two eyes, one struct.

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🔥 SEE ALSO 🔥

go read these next, bestie, the lore continues:

• Kernel file ./drivers/thunderbolt/debugfs.c
• tb_switch_debugfs_init(9)
• tb_switch_debugfs_remove(9)
• tb_service_debugfs_init(9)
• tb_service_debugfs_remove(9)
• tb_retimer_debugfs_init(9)
• tb_retimer_debugfs_remove(9)

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🌈 friendly reminder: every field name, type, value and tiny weird spelling above is exactly as the manpage gave it. the vibes are new, the facts are untouched. periodt. 💜

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and that's the whole page!! 🎀 sourced from ./drivers/thunderbolt, dated October 2026, and titled struct tb_margining(9) forever and always — mwah, go margin some lanes bestie 🧚💖