I could do 'lsmod' to see which drivers are used and loaded as modules. Is there analog command allowing to see which drivers are build in the kernel, and also used? I mean when I configure kernel I specify [Y]/[M] for a specific driver, if the driver is part of the kernel, e.g. [Y] option, will it show up in 'lsmod' list. Is there a way to see all the drivers which are compiled to the kernel and available for possible use? Is .config part of the compiled kernel?

Usually, the .config used to build the kernel is supposed to be copied to /boot along with the actual kernel itself. So you should be able to grep the contents of it with a command like:

(or whatever your .config is named under /boot)

As for an actual command to pull the same information from the kernel, I don't think there is one. At least, none that I am aware of.

I know that one of the kernel options allows the .config file to actually be built into the kernel, which can then be extracted with a tool or by reading from /proc. But I don't know when this option was added to the kernel, and now many distributions even use the function.

There is nothing in the /boot directory even no kernel (sic!). The system is using OpenBIOS which boots kernel from predefined address in the flash.

I saw the option to include .config in 2.6 kernel, don't remember seeing it in 2.4 (but I didn't look thoroughly back then), but it sure would have been nice to have a single command to pull out "[Y]/[M]" info from the kernel.

Have a look for /proc/config.gz