[coreboot] Re: Makefile classes-y vs subdirs-y

[Patrick Georgi]

libpayload uses both.

For example, line 52 defines a class "libcbfs", line 64 adds the subdir "libcbfs".And
https://elixir.bootlin.com/coreboot/latest/source/payloads/libpayload/libcbf... adds its sources to the libcbfs class.

Roughly speaking: subdirs-y just makes the build system scan the Makefile in those subdirs. classes-y creates a new type of build artifact (e.g. bootblock/romstage/ramstage in coreboot, or the various libraries in libpayload), and then $classname-y collects the sources related to that artifact.

Hope this helps,
Patrick