drm_dp_lttpr_count(9)

🌸 drm_dp_lttpr_count(9) — Kernel API Manual, bestie edition 🌸

okay so picture this: it's the kernel API manual, the page is literally called drm_dp_lttpr_count(9), and it is exactly the lowkey hero you didn't know you needed. she counts LTTPRs. that's it. that's the whole vibe. and honestly? iconic. 💅

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✨ NAME ✨

drm_dp_lttpr_count — get the number of detected LTTPRs 💖

🦋 SYNOPSIS 🦋

int drm_dp_lttpr_count (const u8 caps[DP_LTTPR_COMMON_CAP_SIZE] );

🎀 ARGUMENTS 🎀

• caps — the LTTPR common capabilities, bestie. that's the whole argument. she's a const u8 array, size DP_LTTPR_COMMON_CAP_SIZE, and she's carrying the tea.

💜 DESCRIPTION 💜

okay so real talk: this function gets the number of detected LTTPRs, pulling it straight out of the LTTPR common capabilities info. that's it. that's the assignment. she reads the caps, she tells you how many LTTPRs are in the building. no cap. ✨

🔥 RETURN 🔥

so what does she give you back? listen up, this part matters:

• -ERANGE — if more than the supported number (8) of LTTPRs are detected 😭 too many besties in the group chat, she's calling it.
• -EINVAL — if the DP_PHY_REPEATER_CNT register contains an invalid value 💀 that register said something unhinged and she's not entertaining it.
• otherwise — the number of detected LTTPRs 👑 the happy path, the main character ending, slay.

💫 SEE ALSO 💫

okay bestie this list is long but we don't skip, we don't scroll past, we show respect. the kernel file ./drivers/gpu/drm/display/drm_dp_helper.c lives here, plus all of these legends:

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_read_desc(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_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)

ngl that's a lot of cross-references and every single one of them stayed. we ate and left no crumbs. 🍓

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alright bestie, that's the page! this little cutie lives in ./drivers/gpu/drm/display and the version stamp is reading October 2026 — so yeah, she's from the future, she's booked, she's busy, and she's counting LTTPRs. mwah 💋🫶 periodt.