snd_hdac_acomp_get_eld(9)

📦 version 7.3.1, in nixpkgs unstable

💖 snd_hdac_acomp_get_eld — the Kernel API Manual of it all 💖

okay bestie, so this is <rainbow>snd_hdac_acomp_get_eld` from the Kernel API Manual — yes, the whole function name IS the manual name, we love a title drop 💅. It's a function, it lives in the kernel's HD-audio land, and it's about scooching ELD bytes and audio state across the component gap so the graphics driver and the audio driver can be besties. Let's get into it 🫶

✨ SYNOPSIS ✨

like, literally the whole signature, verbatim, no cap:

int snd_hdac_acomp_get_eld (struct hdac_device *codec , hda_nid_t nid ,
int dev_id , bool *audio_enabled , char *buffer , int max_bytes );

one line if you're fancy:

int snd_hdac_acomp_get_eld (struct hdac_device *codec, hda_nid_t nid, int dev_id, bool *audio_enabled, char *buffer, int max_bytes);

🎀 ARGUMENTS 🎀

okay so here's who's who at the function party:

  • codec — the HDA codec. main character energy, obviously 🔥
  • nid — the pin widget NID. the specific pin we're talking about 👑
  • dev_id — device identifier. its little ID card 🪪
  • audio_enabled — the pointer to store the current audio state. it's a bool *, so you're writing through it, not reading 🫶
  • buffer — the buffer pointer to store ELD bytes. this is where the ELD actually lands 📦
  • max_bytes — the max bytes to be stored on buffer. cap it, bestie 🧢

🌸 DESCRIPTION 🌸

so, big vibe check first: this function is supposed to be used only by a HD-audio controller driver that needs the interaction with graphics driver. only by that guy. iykyk 🙈

what it actually does is two things at once, which is giving multitasking icon:

  • it queries the current state of the audio on the given digital port, and
  • it fetches the ELD bytes onto the given buffer 💫

and then it returns... okay hold on, the return value situation is a little unhinged, so pay attention:

  • it returns the number of bytes for the total ELD data,
  • zero for invalid ELD,
  • or a negative error code. 😭

here's the part that trips people up — the return size is the total bytes required for the whole ELD bytes, so it may be over max_bytes. like, it can absolutely be bigger than the cap you gave it. and if it is over max_bytes, that implies that only a part of ELD bytes have been fetched. so a big number isn't an error, it's a "hey, this got truncated, the full thing is actually this many bytes" situation. don't panic, just read the number correctly 🙏

⭐ SEE ALSO ⭐

go read these next, they're literally right there:

🌈 tiny reminder bestie: don't call this from just anywhere — it's for a HD-audio controller driver that needs graphics-driver interaction, periodt. and when the return size is over max_bytes, you got a partial ELD, not a bug 💀

okay that's the whole page!! this little gem lives under ./sound/hda/core, and this edition is dated October 2026 — mwah, go get that ELD 💋🎀🦋

📦 where this page comes from