drm_dp_mst_dpcd_read(9)

💅 NAME 💅

drm_dp_mst_dpcd_read — okay so this is the one that reads a whole series of bytes straight out of the DPCD via sideband 🦋✨

(it's the drm_dp_mst_dpcd_read(9) entry, from the Kernel API Manual, bestie — that's the whole vibe up top)

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✨ SYNOPSIS ✨

ssize_t drm_dp_mst_dpcd_read (struct drm_dp_aux *aux , unsigned int
offset , void *buffer , size_t size );

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🎀 ARGUMENTS 🎀

• aux — the fake sideband AUX CH 👀 yes bestie, fake, that's literally the word in the manpage, don't come for me
• offset — the address of the (first) register you wanna read 📍
• buffer — where the register values get stored, hand it a place to live 🏠
• size — how many bytes are in buffer, the count, the amount, the number fr fr

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🔥 DESCRIPTION 🔥

So it does exactly the same thing for remote devices via sideband messaging that drm_dp_dpcd_read does for local devices via the actual AUX CH 💫

like... same energy, different transport. remote devices get the sideband messaging treatment, local devices get the real AUX CH. that's the whole bit. iykyk 🫶

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⭐ RETURN ⭐

You get back the number of bytes read 📖 — or a negative error code if it failed 😭 (so like, always check, no cap).

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🌈 SEE ALSO 🌈

Kernel file ./drivers/gpu/drm/display/drm_dp_mst_topology.c (that's where the lore lives 📂), plus the whole extended fam — all of these, in order, zero skips:

dp mst helper(9), Branch device and port refcounting(9), drm_dp_mst_get_mstb_malloc(9), drm_dp_mst_put_mstb_malloc(9), drm_dp_mst_get_port_malloc(9), drm_dp_mst_put_port_malloc(9), drm_dp_mst_topology_try_get_mstb(9), drm_dp_mst_topology_get_mstb(9), drm_dp_mst_topology_put_mstb(9), drm_dp_mst_topology_try_get_port(9), drm_dp_mst_topology_get_port(9), drm_dp_mst_topology_put_port(9), drm_dp_mst_dpcd_write(9), drm_dp_mst_connector_late_register(9), drm_dp_mst_connector_early_unregister(9), drm_dp_add_payload_part1(9), drm_dp_remove_payload_part1(9), drm_dp_remove_payload_part2(9), drm_dp_add_payload_part2(9), drm_dp_get_vc_payload_bw(9), drm_dp_read_mst_cap(9), drm_dp_mst_topology_mgr_set_mst(9), drm_dp_mst_topology_queue_probe(9), drm_dp_mst_topology_mgr_suspend(9), drm_dp_mst_topology_mgr_resume(9), drm_dp_mst_hpd_irq_handle_event(9), drm_dp_mst_hpd_irq_send_new_request(9), drm_dp_mst_detect_port(9), drm_dp_mst_edid_read(9), drm_dp_mst_get_edid(9), drm_dp_atomic_find_time_slots(9), drm_dp_atomic_release_time_slots(9), drm_dp_mst_atomic_setup_commit(9), drm_dp_mst_atomic_wait_for_dependencies(9), drm_dp_mst_root_conn_atomic_check(9), drm_dp_mst_update_slots(9), drm_dp_check_act_status(9), drm_dp_calc_pbn_mode(9), drm_dp_mst_dump_topology(9), drm_dp_mst_port_downstream_of_parent(9), drm_dp_mst_add_affected_dsc_crtcs(9), drm_dp_mst_atomic_enable_dsc(9), drm_dp_mst_atomic_check_mgr(9), drm_dp_mst_atomic_check(9), drm_atomic_get_mst_topology_state(9), drm_atomic_get_old_mst_topology_state(9), drm_atomic_get_new_mst_topology_state(9), drm_dp_mst_topology_mgr_init(9), drm_dp_mst_topology_mgr_destroy(9), drm_dp_mst_register_i2c_bus(9), drm_dp_mst_unregister_i2c_bus(9), drm_dp_mst_is_virtual_dpcd(9), drm_dp_mst_aux_for_parent(9), drm_dp_mst_dsc_aux_for_port(9)

like genuinely that's the whole friend group, go say hi 💜👑

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lowkey a tiny page but it's iconic and it does exactly one job and does it well. main character energy, honestly. 💅

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🎀 okay that's a wrap bestie 🎀 — this one came from ./drivers/gpu/drm/display (that's the source path, mwah 😘), stamped October 2026, and the page is drm_dp_mst_dpcd_read(9) in case you forgot already 🙈 love u, go read some DPCD bytes 💖✨🦋