drm_dp_dpcd_read(9)

📦 version 7.3.1, in nixpkgs unstable

✨ NAME ✨

drm_dp_dpcd_read(9) is straight out of the Kernel API Manual, and she does exactly what it says on the tin: read a series of bytes from the DPCD. bestie behavior, honestly.

🌸 SYNOPSIS 🌸

ssize_t drm_dp_dpcd_read (struct drm_dp_aux *aux , unsigned int offset ,
       void *buffer , size_t size );

🎀 ARGUMENTS 🎀

  • aux — the DisplayPort AUX channel (SST or MST). pick your flavor.
  • offset — address of the (first) register to read. where we start, iykyk.
  • buffer — buffer to store the register values. the little basket for the bytes.
  • size — number of bytes in buffer. how many bytes are invited to the party.

💅 DESCRIPTION 💅

Okay so on success, this returns the number of bytes transferred. On failure? A negative error code, obviously.

-EIO is returned if the request was NAKed by the sink or if the retry count was exceeded. If not all bytes were transferred, this function returns -EPROTO. Errors from the underlying AUX channel transfer function are propagated to the caller, with the exception of -EBUSY (which causes the transaction to be retried). no cap, that -EBUSY exception is the plot twist.

lowkey important: in most of the cases you want to use drm_dp_dpcd_read_data instead. slay that other function instead, bestie 💅

🌈 SEE ALSO 🌈

the whole dp helpers friend group, assembled:

slay and goodbye, bestie 💖 — source/version: ./drivers/gpu/drm/display; date: October 2026 🫶✨

📦 where this page comes from