STRUCT DRM_DP_MST_BRANCH(9)

struct drm_dp_mst_branch(9) 💅✨

okay so bestie, this is the Kernel API Manual entry for struct drm_dp_mst_branch — the MST branch device struct. It’s giving kernel-internals main character energy, and we’re gonna go through every field, no skips. 🫶

🌸 NAME 🌸

struct drm_dp_mst_branch — MST branch device. 💖

✨ SYNOPSIS ✨

Here’s the struct in all its glory, literally character-for-character:

struct drm_dp_mst_branch {
    struct kref topology_kref;
    struct kref malloc_kref;
  #if IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS);
    struct drm_dp_mst_topology_ref_history topology_ref_history;
  #endif;
    struct list_head destroy_next;
    u8 rad[8];
    u8 lct;
    int num_ports;
    struct list_head ports;
    struct drm_dp_mst_port *port_parent;
    struct drm_dp_mst_topology_mgr *mgr;
    bool link_address_sent;
    guid_t guid;
};

🦋 Members 🦋

• topology_kref — the refcount for this branch device’s lifetime in the topology. Only the DP MST helpers should need to touch this, bestie. 💅
• malloc_kref — the refcount for the memory allocation containing this structure. See drm_dp_mst_get_mstb_malloc and drm_dp_mst_put_mstb_malloc. 🎀
• topology_ref_history — a history of each topology reference/dereference. See CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS. ✨
• destroy_next — linked-list entry used by drm_dp_delayed_destroy_work. 🌈
• rad — Relative Address of the MST branch. For drm_dp_mst_topology_mgr.mst_primary, the rad[8] are all 0, unset and unused. For MST branches connected after mst_primary, in each element of rad[] the nibbles are ordered by the most significant 4 bits first and the least significant 4 bits second. 🧚
• lct — Link count total to talk to this branch device. 💬
• num_ports — number of ports on the branch. 🔢
• ports — the list of ports on this branch device. This should be considered protected for reading by drm_dp_mst_topology_mgr.lock. There are two exceptions to this: drm_dp_mst_topology_mgr.up_req_work and drm_dp_mst_topology_mgr.work, which do not grab drm_dp_mst_topology_mgr.lock during reads but are the only updaters of this list and are protected from updating the list concurrently by drm_dp_mst_topology_mgr.probe_lock. 💜
• port_parent — pointer to the port parent, NULL if toplevel. 🫶
• mgr — topology manager for this branch device. 👑
• link_address_sent — if a link address message has been sent to this device yet. 📬
• guid — guid for DP 1.2 branch device. A port under this branch can be identified by port #. 🆔

🌟 Description 🌟

This structure represents an MST branch device. There is one primary branch device at the root, along with any other branches connected to downstream port of parent branches. 🦋

🔥 SEE ALSO 🔥

Kernel file: ./include/drm/display/drm_dp_mst_helper.h

• struct drm_dp_mst_port(9)
• struct drm_dp_mst_atomic_payload(9)
• struct drm_dp_mst_topology_state(9)
• struct drm_dp_mst_topology_mgr(9)
• enum drm_dp_mst_mode(9)
• __drm_dp_mst_state_iter_get(9)
• for_each_oldnew_mst_mgr_in_state(9)
• for_each_old_mst_mgr_in_state(9)
• for_each_new_mst_mgr_in_state(9)

source/version: ./include/drm/display · date: October 2026 · page: struct drm_dp_mst_branch(9) 🫶✨💅