DOKK / manpages / debian 11 / avr-libc / todo.3avr.en
todo(3avr) avr-libc todo(3avr)

todo - Todo List

From email with Marek: On smaller devices (all except ATmega64/128), __SPM_REG is in the I/O space, accessible with the shorter 'in' and 'out' instructions - since the boot loader has a limited size, this could be an important optimization.
Fri Jan 1 2021 Version 2.0.0