drm_dp_read_desc(9)

💅 drm_dp_read_desc(9) — like, the Kernel API Manual one

okay so bestie, this is drm_dp_read_desc, straight out of the Kernel API Manual, and it's literally about reading a sink/branch descriptor from DPCD. Yes, that's a lot of acronyms, we'll get there 🫶

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✨ NAME ✨

drm_dp_read_desc — read sink/branch descriptor from DPCD 💖

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🌸 SYNOPSIS 🌸

int drm_dp_read_desc (struct drm_dp_aux *aux , struct drm_dp_desc *desc
, bool is_branch );

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🎀 ARGUMENTS 🎀

• aux — the DisplayPort AUX channel, your little messenger ✨
• desc — the device descriptor that gets filled from DPCD, like an empty cup waiting for boba 🧋
• is_branch — true for branch devices, false for sink devices. it's giving "pick a lane" 😌

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🦋 DESCRIPTION 🦋

okay so what this does is literally read DPCD 0x400 (that's the sink one) or 0x500 (that's the branch one) right into desc. and bestie, it also debug logs the identification, because receipts ✨

Returns 0 on success or a negative error code on failure. no cap, that's the whole vibe check 🔥

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💜 SEE ALSO 💜

Kernel file ./drivers/gpu/drm/display/drm_dp_helper.c — and honestly the whole friend group:

• dp helpers(9)
• drm_dp_phy_name(9)
• drm_dp_lttpr_wake_timeout_setup(9)
• dp helpers(9)
• drm_dp_dpcd_probe(9)
• drm_dp_dpcd_set_powered(9)
• drm_dp_dpcd_set_probe(9)
• drm_dp_dpcd_read(9)
• drm_dp_dpcd_write(9)
• drm_dp_dpcd_read_link_status(9)
• drm_dp_dpcd_read_phy_link_status(9)
• drm_dp_link_power_up(9)
• drm_dp_link_power_down(9)
• drm_dp_dpcd_write_payload(9)
• drm_dp_dpcd_clear_payload(9)
• drm_dp_dpcd_poll_act_handled(9)
• drm_dp_downstream_is_type(9)
• drm_dp_downstream_is_tmds(9)
• drm_dp_send_real_edid_checksum(9)
• drm_dp_read_dpcd_caps(9)
• drm_dp_read_downstream_info(9)
• drm_dp_downstream_max_dotclock(9)
• drm_dp_downstream_max_tmds_clock(9)
• drm_dp_downstream_min_tmds_clock(9)
• drm_dp_downstream_max_bpc(9)
• drm_dp_downstream_420_passthrough(9)
• drm_dp_downstream_444_to_420_conversion(9)
• drm_dp_downstream_rgb_to_ycbcr_conversion(9)
• drm_dp_downstream_mode(9)
• drm_dp_downstream_id(9)
• drm_dp_downstream_debug(9)
• drm_dp_subconnector_type(9)
• drm_dp_set_subconnector_property(9)
• drm_dp_read_sink_count_cap(9)
• drm_dp_read_sink_count(9)
• drm_dp_remote_aux_init(9)
• drm_dp_aux_init(9)
• drm_dp_aux_register(9)
• drm_dp_aux_unregister(9)
• drm_dp_psr_setup_time(9)
• drm_dp_start_crc(9)
• drm_dp_stop_crc(9)
• drm_dp_dump_lttpr_desc(9)
• drm_dp_dsc_sink_bpp_incr(9)
• drm_dp_dsc_slice_count_to_mask(9)
• drm_dp_dsc_sink_slice_count_mask(9)
• drm_dp_dsc_sink_max_slice_count(9)
• drm_dp_dsc_sink_line_buf_depth(9)
• drm_dp_dsc_sink_supported_input_bpcs(9)
• drm_dp_dsc_sink_max_slice_throughput(9)
• drm_dp_dsc_branch_max_overall_throughput(9)
• drm_dp_dsc_branch_max_line_width(9)
• drm_dp_read_lttpr_common_caps(9)
• drm_dp_read_lttpr_phy_caps(9)
• drm_dp_lttpr_count(9)
• drm_dp_lttpr_max_link_rate(9)
• drm_dp_lttpr_set_transparent_mode(9)
• drm_dp_lttpr_init(9)
• drm_dp_lttpr_max_lane_count(9)
• drm_dp_lttpr_voltage_swing_level_3_supported(9)
• drm_dp_lttpr_pre_emphasis_level_3_supported(9)
• drm_dp_get_phy_test_pattern(9)
• drm_dp_set_phy_test_pattern(9)
• drm_dp_as_sdp_supported(9)
• drm_dp_vsc_sdp_supported(9)
• drm_dp_vsc_sdp_pack(9)
• drm_dp_get_pcon_max_frl_bw(9)
• drm_dp_pcon_frl_prepare(9)
• drm_dp_pcon_is_frl_ready(9)
• drm_dp_pcon_frl_configure_1(9)
• drm_dp_pcon_frl_configure_2(9)
• drm_dp_pcon_reset_frl_config(9)
• drm_dp_pcon_frl_enable(9)
• drm_dp_pcon_hdmi_link_active(9)
• drm_dp_pcon_hdmi_link_mode(9)
• drm_dp_pcon_hdmi_frl_link_error_count(9)
• drm_dp_pcon_pps_default(9)
• drm_dp_pcon_pps_override_buf(9)
• drm_edp_backlight_set_level(9)
• drm_edp_backlight_enable(9)
• drm_edp_backlight_disable(9)
• drm_edp_backlight_init(9)
• drm_panel_dp_aux_backlight(9)
• drm_dp_link_symbol_cycles(9)
• drm_dp_bw_overhead(9)
• drm_dp_bw_channel_coding_efficiency(9)
• drm_dp_max_dprx_data_rate(9)

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and that's the whole page, bestie 🌈 this little legend lives in ./drivers/gpu/drm/display, dated October 2026 — mwah, periodt 💅👑