Device probing and driver attach

["Rocky Hotas" <rockyhotas%post.com@localhost>]

Hi all!
I hope this is appropriate to this list.
When the OS is booted, it still doesn't know the devices that will be
present in the current machine and it doesn't then know what drivers
should be used. After the bootstrap, the system autoconfiguration is
performed: according to autoconf(9), "Autoconfiguration is the process
of matching hardware devices with an appropriate device driver". Here
follow some questions:
- For each detected device, the probe function of *any* driver is called?
It seems a cumbersome procedure, but boot time is not that much long.
- In principle, if one built a custom kernel including *only* the drivers
needed by its current machine, would the boot time get significantly
reduced?
- When a BIOS does not perform this operation, is during the
autoconfiguration that device BARs are written by the OS?
- autoconf(9) specifies that "The autoconfiguration framework itself is
implemented within the file sys/kern/subr_autoconf.c". I am not that
skilled with it: which is, in that file, the routine that searches for
new devices and calls driver probe functions?
Thanks to anyone who can answer to even just one... or half :) of the
questions.

Rocky