Understanding the function of the common core files

[mcuee]

If we look at the avrdude source codes, other than the doc, msvc helper files, then there are CMake/Autotools scripts, programmer/bootloader specific files, libusb/hidapi/serial/parallel transport files, avrdude.conf related files, some help files (like list.c) and some core common files.
https://github.com/avrdudes/avrdude/tree/main/src

I think the core common files include the following. Please help to see if I miss any other important files.
avr.c
avrpart.c
developer_opts.c
fileio.c
main.c
pgm.c
pgmtype.c
term.c
update.c

[mcuee]

It will be great that developers who are familiar with the code base can shed lights on the functions of the core common files. Thanks.

[stefanrueger]

I think you've pretty much presented the main organising principles of the AVRDUDE source very well. Worth mentioning the separation

• Library functionality for libavrdude (functions for programmers and common programming functions) that could in theory be used for many different application types (CLI, GUI, daemon, ...) with the functions and structures declared in libavrdude.h
• Stand alone CLI, which is basically main.c, developer_opts.c and term.c, that links against libavrdude.a

The library functions historically were part of the stand-alone CLI, so they need a lot of work to get into library "shape": removing exit(n), making the functions re-entrant, thread-safe, fix memory leaks (though they will not be significant),

Also worth pointing out that avrdude.conf, config_gram.y, lexer.l and config.c are a very important part, the "knowledge base" of AVRDUDE and actually almost 40% of the code (in terms of number of lines). If you want to get familiar with the code I recommend starting to read the files you mentioned. For example, follow through what happens when someone types avrdude -U in.hex -p ... -c ...

Whilst there is an excellent documentation of the stand-alone CLI, there is only scarce documentation of the libavrdude functions (as far as I can see), and the latter are "in flow".