dm_mst_test...ream_present(9)

💅 dm_mst_test_retrieve_downstream_present(9) — Kernel API Manual, but make it make sense 🫶

okay so bestie, this is a page straight out of the Kernel API Manual and it's about a single KUnit test that checks DPCD 0x05 parsing. tiny test, huge main character energy. let's get into it ✨

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🌸 NAME 🌸

dm_mst_test_retrieve_downstream_present — the test that checks retrieve parses DPCD 0x05. literally that's the whole vibe. 🎀

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✨ SYNOPSIS ✨

void dm_mst_test_retrieve_downstream_present (struct kunit *test );

no cap, that's the whole signature. one argument, zero drama. 💅

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🦋 ARGUMENTS 🦋

• test — the KUnit test context. that's it, that's the argument. she's the context holder, the main character's backstage pass 👑

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💖 DESCRIPTION 💖

so here's the tea ☕ — this test verifies that retrieve_downstream_port_device reads DP_DOWNSTREAMPORT_PRESENT over a mock AUX channel, and then caches the parsed downstream port fields.

like. it's giving "did the parsing actually happen and did we keep the results". mock AUX channel does the heavy lifting so nobody has to poke real hardware, and the test just sits there like "did you cache it tho 👀". obsessed.

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🌈 SEE ALSO 🌈

okay this list is LONG and i'm not skipping a single one, because every friend in this group chat matters 🫶

the file itself:

• Kernel file ./drivers/gpu/drm/amd/display/amdgpu_dm/tests/amdgpu_dm_mst_types_test.c

and all her siblings, in order, no cap:

• dm_mst_test_needs_dsc_aux_workaround_match(9)
• dm_mst_test_needs_dsc_aux_workaround_rev12(9)
• dm_mst_test_needs_dsc_aux_workaround_wrong_dev_id(9)
• dm_mst_test_needs_dsc_aux_workaround_wrong_rev(9)
• dm_mst_test_needs_dsc_aux_workaround_low_sink_count(9)
• dm_mst_test_needs_dsc_aux_workaround_zero_sink_count(9)
• dm_mst_test_pbn_divider_null_link(9)
• dm_mst_test_pbn_divider_uses_link_bandwidth(9)
• dm_mst_test_reset_connector_setting(9)
• dm_mst_test_retrieve_downstream_no_aux(9)
• dm_mst_test_retrieve_downstream_aux_error(9)
• dm_mst_test_retrieve_branch_no_parent(9)
• dm_mst_test_retrieve_branch_reads_oui(9)
• dm_mst_test_aux_result_success(9)
• dm_mst_test_aux_result_eio(9)
• dm_mst_test_aux_result_ebusy(9)
• dm_mst_test_aux_result_timeout(9)
• dm_mst_test_aux_transfer_native_read(9)
• dm_mst_test_aux_transfer_native_write(9)
• dm_mst_test_aux_transfer_partial_write(9)
• dm_mst_test_aux_transfer_error_result(9)
• dm_mst_test_aux_transfer_hpd_discon_quirk(9)
• dm_mst_test_aux_transfer_non_ack_reply(9)
• dm_mst_test_fill_payload_flags_native_write(9)
• dm_mst_test_fill_payload_flags_native_read(9)
• dm_mst_test_fill_payload_flags_i2c_read_mot(9)
• dm_mst_test_fill_payload_flags_write_status(9)
• dm_mst_test_msg_ready_mask(9)
• dm_mst_test_select_esi_dpcd_legacy(9)
• dm_mst_test_select_esi_dpcd_esi(9)
• dm_mst_test_sideband_msg_ready_no_ready_bits(9)
• dm_mst_test_sideband_msg_ready_read_error(9)
• dm_mst_test_sideband_msg_ready_without_mst_state(9)
• dm_mst_test_down_rep_msg_ready_wrapper(9)
• dm_mst_test_initialize_dp_connector_edp(9)
• dm_mst_test_initialize_dp_connector_mst(9)
• dm_mst_test_atomic_best_encoder(9)
• dm_mst_test_create_fake_mst_encoders(9)
• dm_mst_test_atomic_check_no_old_crtc(9)
• dm_mst_test_detect_unregistered(9)
• dm_mst_test_fp_guarded_public_stubs(9)

that's the whole squad. tag yourself, i'm dm_mst_test_aux_transfer_hpd_discon_quirk 💀

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💜 friendly reminder: this is a test page, so the "danger" here is just your brain melting from the sheer number of dm_mst_test_* names in a row. hydrate. 🌸

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and that's the page!! source/version situation is ./drivers/gpu/drm/amd/display/... dated October 2026, and yes bestie the page header said dm_mst_test...ream_present(9) both at the top and the bottom because manpages love a symmetrical moment 💅✨ bye ily, go read the other 41 pages 🫶🎀