STRUCT TB_BANDWIDTH_GROUP(9)

okay bestie, this is the struct tb_bandwidth_group(9) page from the Kernel API Manual, and it’s literally the bandwidth management group struct. Let’s get into every detail, no skipping 💅✨

💖 NAME 💖

struct tb_bandwidth_group — Bandwidth management group. That’s the whole vibe: a group for managing bandwidth, and yes it’s giving main character energy 🎀

✨ SYNOPSIS ✨

the struct looks exactly like this:

       struct tb_bandwidth_group {
           struct tb *tb;
           int index;
           struct list_head ports;
           int reserved;
           struct delayed_work release_work;
        };

🧚 Members 🧚

• tb — Pointer to the domain the group belongs to. It knows its domain, periodt 💫
• index — Index of the group (aka Group_ID). Valid values 1-7. Like, only 1 through 7, bestie, that’s the range 🔥
• ports — DP IN adapters belonging to this group are linked here. All the DP IN adapters in this group are hooked up right here 🫶
• reserved — Bandwidth released by one tunnel in the group, available to others. This is reported as part of estimated_bw for the group. So yes, that reserved bandwidth is part of the group’s estimated_bw report 💅
• release_work — Worker to release the reserved if it is not used by any of the tunnels. It’s the cleanup crew for unused reserved bandwidth 🧹

🌸 Description 🌸

okay so any tunnel that requires isochronous bandwidth — that’s DP for now — is attached to a bandwidth group. All tunnels going through the same USB4 links share the same group and can dynamically distribute the bandwidth within the group. It’s giving shared-resource main character energy, but make it USB4 🌈

👑 SEE ALSO 👑

Kernel file ./drivers/thunderbolt/tb.h, plus the whole cross-ref clique:

• struct tb_nvm(9)
• enum tb_switch_tmu_mode(9)
• struct tb_switch_tmu(9)
• struct tb_switch(9)
• struct tb_port(9)
• struct usb4_port(9)
• struct tb_retimer(9)
• struct tb_path_hop(9)
• enum tb_path_port(9)
• struct tb_path(9)
• struct tb_cm_ops(9)
• tb_upstream_port(9)
• tb_is_upstream_port(9)
• tb_port_has_remote(9)
• tb_domain_event(9)
• tb_switch_for_each_port(9)
• tb_switch_downstream_port(9)
• tb_switch_depth(9)
• tb_switch_is_icm(9)
• tb_switch_tmu_is_configured(9)
• tb_switch_tmu_is_enabled(9)
• tb_switch_clx_is_enabled(9)
• tb_port_path_direction_downstream(9)
• tb_for_each_port_on_path(9)
• tb_for_each_upstream_port_on_path(9)
• tb_path_for_each_hop(9)
• tb_downstream_route(9)
• tb_xdomain_downstream_port(9)
• usb4_switch_version(9)
• tb_switch_is_usb4(9)
• enum usb4_sb_target(9)
• enum usb4_margin_sw_error_counter(9)
• struct usb4_port_margining_params(9)

that’s the whole page, bestie 🫶 — source ./drivers/thunderbolt, dated October 2026, from the Kernel API Manual, page struct tb_bandwidth_group(9). bye 💅✨