Relevant micropython commits:
01374d941f9d7398e35990b574769b20c6779457 py/mpconfig.h: Define initial templates for "feature levels".
7b89ad8dbf432ab51eea6d138e179bf51394c786 py/vm: Add a fast path for LOAD_ATTR on instance types.
68219a295c75457c096ac42dbe8411b84e1e1a51 stm32: Enable LOAD_ATTR fast path, and map lookup caching on >M0.
e0bf4611c3a8b23b3c52e6a7804aac341ac3a87d py: Only search frozen modules when '.frozen' is found in sys.path.
f2040bfc7ee033e48acef9f289790f3b4e6b74e5 py: Rework bytecode and .mpy file format to be mostly static data.
926b554dafffa1e9bd80aa12fea5c621221c9d79 extmod/moduos: Create general uos module to be used by all ports.
2b409ef8a46015f8f3bd20bc44e644637dbe9bd3 unix/moduos: Convert module to use extmod version.
47f634300c5572571816817f16836113c98814ae py: Change makemoduledefs process so it uses output of qstr extraction.
0e7bfc88c6ac6b5d64240f91183a3cfe2ab67ade all: Use mp_obj_malloc everywhere it's applicable.
2a6ba47110be88ff1e1f5abd1bd76c353447884c py/obj: Add static safety checks to mp_obj_is_type().
Changes in firmware/mpconfigport.h are minimal:
* $VFS_FAT is dropped because it is irrelevant without $VFS
* $REVERSE_SPECIAL_METHODS is added, to push down on code size
* $THREAD is disabled unconditionally
unix/mpconfigport.h is reordered and modified to match
firmware/mpconfigport.h as much as possible, while selectively enabling
some needed features.
Notably, $USE_READLINE is enabled unconditionally
