Package overrides

Buildroot has a built-in mechanism — <PACKAGE>_OVERRIDE_SRCDIR — that tells it to rsync a package from a local directory instead of downloading the upstream tarball. The MDS tree wires this up through two files in mds_external/.

overrides.mk (tracked)

mds_external/overrides.mk is the versioned override file applied by all defconfigs (BR2_PACKAGE_OVERRIDE_FILE). It contains the overrides that must be active in CI and on every machine. Today this is just one entry:

ESP_HOSTED_OVERRIDE_SRCDIR = $(TOPDIR)/../../src/esp-hosted

src/esp-hosted/ is a git submodule pinned to the fork that carries the two patches needed for the MDS board (SPI_MODE = 1, register_hs_disable_pin, …). The CI checks out submodules recursively so this just works.

local.mk (gitignored)

overrides.mk ends with:

-include $(BR2_EXTERNAL_MDS_PATH)/local.mk

so any local.mk you drop next to it is picked up automatically. This is the place for personal, development-only overrides — typical example: a kernel checkout you iterate on outside Buildroot. See local.mk.example for the template.

Available variables

Any Buildroot package can be overridden by setting <UPPERCASED_PACKAGE_NAME>_OVERRIDE_SRCDIR. Examples:

The path is relative to Buildroot's $(TOPDIR). In this repo Buildroot lives under build/buildroot-2026.02.1/, so $(TOPDIR)/../../src/foo resolves to <repo>/src/foo.

See the Buildroot manual on override files for the full reference.