drm_dp_bw_overhead(9)

📦 version 7.3.1, in nixpkgs unstable

💖 NAME 💖

okay bestie, welcome to drm_dp_bw_overhead(9) from the Kernel API Manual — it's the helper that calculates the BW overhead of a DP link stream. 💅

✨ SYNOPSIS ✨

int drm_dp_bw_overhead (int lane_count , int hactive , int
       dsc_slice_count , int bpp_x16 , unsigned long flags );

🎀 ARGUMENTS 🎀

  • lane_count — DP link lane count. literally how many lanes we're working with.
  • hactive — pixel count of the active period in one scanline of the stream.
  • dsc_slice_count — number of slices for DSC, or '0' for non-DSC.
  • bpp_x16 — bits per pixel in .4 binary fixed point.
  • flags — DRM_DP_OVERHEAD_x flags. yes, that exact shape.

🦋 DESCRIPTION 🦋

Calculate the BW allocation overhead of a DP link stream, depending on the link's:

  • lane_count
  • SST/MST mode (flags / DRM_DP_OVERHEAD_MST)
  • symbol size (flags / DRM_DP_OVERHEAD_UHBR)
  • FEC mode (flags / DRM_DP_OVERHEAD_FEC)
  • SSC/REF_CLK mode (flags / DRM_DP_OVERHEAD_SSC_REF_CLK)

as well as the stream's:

  • hactive timing
  • bpp_x16 color depth
  • compression mode (dsc_slice_count != 0)

Note that this overhead doesn't account for the 8b/10b, 128b/132b channel coding efficiency, for that see drm_dp_link_bw_channel_coding_efficiency.

Returns the overhead as 100% + overhead% in 1ppm units. 🫶

🌈 SEE ALSO 🌈

okay the guest list is LONG and everyone's invited — no cuts, no skips:

okay that's the whole page, bestie — source/version straight from ./drivers/gpu/drm/display, October 2026, and drm_dp_bw_overhead(9) is out. 💅✨

📦 where this page comes from