drm_helper_...nector_modes(9)

📦 version 7.3.1, in nixpkgs unstable

✨ drm_helper_probe_single_connector_modes(9) ✨

okay bestie, we're in the Kernel API Manual today and this one is literally the glow-up routine for your display modes 💅 buckle up, it's giving "makeover montage but for connectors".

🎀 NAME 🎀

drm_helper_probe_single_connector_modes — get the complete set of display modes. like, all of them. the whole wardrobe. 👑

🦋 SYNOPSIS 🦋

int drm_helper_probe_single_connector_modes (struct drm_connector
*connector , uint32_t maxX , uint32_t maxY );

🌸 ARGUMENTS 🌸

  • connector — the connector we're probing. this is our main character fr.
  • maxX — max width for modes. the width vibe check.
  • maxY — max height for modes. the height vibe check.

💖 DESCRIPTION 💖

So here's the tea ☕ — based on the helper callbacks that connector implements in struct drm_connector_helper_funcs, we try to detect all the valid modes. no cap, all of them.

Modes get added to the connector's probed_modes list first, and then they get culled (based on validity and the maxX, maxY parameters — yeah, those two) and dropped into the normal modes list. it's giving audition then callback. 🎬

This is intended to be used as a generic implementation of the drm_connector_funcs.fill_modes vfunc, for drivers that use the CRTC helpers for output mode filtering and detection. iykyk.

The basic procedure is literally as follows, step by step, no skipping:

  1. All modes currently on the connector's modes list are marked as stale. like, old news, bestie. 🗑️
  2. New modes are added to the connector's probed_modes list with drm_mode_probed_add. New modes start their life with status as OK — fresh out the box, thriving, unproblematic. ✨ Modes are added from a single source using the following priority order:
    • drm_connector_helper_funcs.get_modes vfunc
    • if the connector status is connector_status_connected, standard VESA DMT modes up to 1024x768 are automatically added (drm_add_modes_noedid)

Finally, modes specified via the kernel command line (video=...) are added in addition to what the earlier probes produced (drm_helper_probe_add_cmdline_mode). These modes are generated using the VESA GTF/CVT formulas. math girlies rise 🧮

  1. Modes are moved from the probed_modes list to the modes list. Potential duplicates are merged together (see drm_connector_list_update). After this step the probed_modes list will be empty again. clean slate, we love a reset 🫶
  2. Any non-stale mode on the modes list then undergoes validation:
    • drm_mode_validate_basic performs basic sanity checks
    • drm_mode_validate_size filters out modes larger than maxX and maxY (if specified)
    • drm_mode_validate_flag checks the modes against basic connector capabilities (interlace_allowed,doublescan_allowed,stereo_allowed)
    • the optional drm_connector_helper_funcs.mode_valid or drm_connector_helper_funcs.mode_valid_ctx helpers can perform driver and/or sink specific checks
    • the optional drm_crtc_helper_funcs.mode_valid, drm_bridge_funcs.mode_valid and drm_encoder_helper_funcs.mode_valid helpers can perform driver and/or source specific checks which are also enforced by the modeset/atomic helpers
  3. Any mode whose status is not OK is pruned from the connector's modes list, accompanied by a debug message indicating the reason for the mode's rejection (see drm_mode_prune_invalid). it's not you it's your status 💀 but don't worry, the debug message explains everything.

🔥 RETURN 🔥

The number of modes found on connector. that's it, that's the number, that's the whole return value 👑

🌈 SEE ALSO 🌈

Kernel file ./drivers/gpu/drm/drm_probe_helper.c, output probing helper overview(9), drm_kms_helper_poll_enable(9), drm_kms_helper_poll_reschedule(9), drm_helper_probe_detect(9), drm_kms_helper_hotplug_event(9), drm_kms_helper_connector_hotplug_event(9), drm_kms_helper_is_poll_worker(9), drm_kms_helper_poll_disable(9), drm_kms_helper_poll_init(9), drm_kms_helper_poll_fini(9), drmm_kms_helper_poll_init(9), drm_connector_helper_hpd_irq_event(9), drm_helper_hpd_irq_event(9), drm_crtc_helper_mode_valid_fixed(9), drm_connector_helper_get_modes_fixed(9), drm_connector_helper_get_modes(9), drm_connector_helper_tv_get_modes(9), drm_connector_helper_detect_from_ddc(9)

and that's the whole page, bestie!! 💜 this little masterpiece lives in ./drivers/gpu/drm and it ate, dated October 2026 — save the date, screenshot it, put it on the fridge 🧚✨💖

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