for_each_old...mgr_in_state(9)

💅 for_each_old...mgr_in_state(9) 💅

okay bestie, so this is a page from the Kernel API Manual, section 9 — yes, the big serious kernel one — and today's main character is for_each_oldnew_mst_mgr_in_state. it's a macro. it's a whole vibe. let's get into it 🎀

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✨ NAME ✨

for_each_oldnew_mst_mgr_in_state — literally just loops over every DP MST topology manager in an atomic update. that's it. that's the whole job. iconic behaviour honestly 🦋

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🌸 SYNOPSIS 🌸

for_each_oldnew_mst_mgr_in_state (__state , mgr , old_state , new_state
, __i );

she takes five things, no more no less. count 'em:

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🫶 ARGUMENTS 🫶

• __state — a struct drm_atomic_commit pointer. the big one. the moment. the atomic commit itself 💫
• mgr — a struct drm_dp_mst_topology_mgr iteration cursor. this is the thing you're actually walking through, one manager at a time.
• old_state — a struct drm_dp_mst_topology_state iteration cursor, but for the old state. the before pic 🙈
• new_state — a struct drm_dp_mst_topology_state iteration cursor, but for the new state. the glow-up pic ✨
• __i — an int iteration cursor, for macro-internal use only. don't touch her, she's busy, she's bookkeeping 🔥

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💜 DESCRIPTION 💜

so what does she actually do? she iterates over all DRM DP MST topology managers in an atomic update — and the way she does it is the whole point: she tracks both old and new state at the same time. two states, one loop. main character energy fr fr 👑

and why do you care? because this is genuinely useful in places where the state delta needs to be considered — for example in atomic check functions. if you need to know what changed, not just what is, this macro is your girl. no cap 💅

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🌈 SEE ALSO 🌈

like, go read these too, they're all connected, iykyk:

• Kernel file ./include/drm/display/drm_dp_mst_helper.h
• struct drm_dp_mst_port(9)
• struct drm_dp_mst_branch(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_old_mst_mgr_in_state(9)
• for_each_new_mst_mgr_in_state(9)

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aaaand that's the page! 🍓 this little beauty lives over in ./include/drm/display, and the version notes say October 2026 — so she's from the future, basically, and she ate. periodt 💀✨ 💖