drm_dp_aux_register(9)

📦 version 7.3.1, in nixpkgs unstable

💅 drm_dp_aux_register(9) — the Kernel API Manual glow-up 🎀

okay so bestie, welcome to the Kernel API Manual entry for drm_dp_aux_register(9) — yes that's the title, yes it's giving "display port aux channel registration" main character energy, and yes we're gonna get through it together. grab a strawberry 🍓 and let's go.

✨ NAME ✨

drm_dp_aux_register — the function that initialises and registers your aux channel. it's literally both things. iconic behavior honestly 👑

🌸 SYNOPSIS 🌸

int drm_dp_aux_register (struct drm_dp_aux *aux );

that's it. one function. one pointer. she's simple but she's powerful 💅

🦋 ARGUMENTS 🦋

  • aux — the DisplayPort AUX channel. that's the whole vibe. it's a struct drm_dp_aux * and she's the star of the show ✨

🔥 DESCRIPTION 🔥

so here's the tea, bestie. this function automatically calls drm_dp_aux_init if that hasn't been done yet. convenient? yes. but there are RULES 😤

you should only call this once the parent of aux, drm_dp_aux.dev, is initialized. do not come for this function before her parent is ready, she will not handle it well.

🫶 for devices that are grandparents of their AUX channels

in this case, drm_dp_aux.dev will typically be the drm_connector device which corresponds to aux. for these devices, the advice is literally:

  • call drm_dp_aux_register in drm_connector_funcs.late_register
  • and likewise call drm_dp_aux_unregister in drm_connector_funcs.early_unregister
⚠️ functions which don't follow this will likely Oops when CONFIG_DRM_DISPLAY_DP_AUX_CHARDEV is enabled. not a cute Oops. a kernel Oops 💀 so please, follow the pattern.

🧚 for devices where the AUX channel is independent

okay so for devices where the AUX channel is a device that exists independently of the drm_device that uses it — think SoCs and bridge devices, iykyk — the recommendation is:

  • call drm_dp_aux_register after a drm_device has been assigned to drm_dp_aux.drm_dev
  • and likewise call drm_dp_aux_unregister once the drm_device should no longer be associated with the AUX channel (e.g. on bridge detach)

like, clean break, no messy strings attached 🎀

⭐ drivers that need the aux channel EARLY

if your driver needs to use the aux channel before either of the two points mentioned above, then you need to call drm_dp_aux_init in order to use the AUX channel before registration. periodt.

🌈 return value

Returns 0 on success or a negative error code on failure. that's the whole vibe check: zero = slay, negative = not slay 😭

💜 SEE ALSO 💜

okay this list is LONG, so buckle up bestie, we're listing every single one because nobody gets left behind 🫶

like I said. LONG. but we got through it together 💖

and that's the page!! before you go, the cute little sign-off details: this came from the source at ./drivers/gpu/drm/display, dated October 2026, and it's the drm_dp_aux_register(9) page from the Kernel API Manual. no cap, that's everything. now go register your aux channel responsibly 🦋✨💜

📦 where this page comes from