How do I get the ath9k driver of backports-3.12-8 installed on Xubuntu 13.10?

For those who might stumble across this question, like I just did:

This leaves me with following "missing-prototypes ERROR":

cc -Wall -Wmissing-prototypes -Wstrict-prototypes -O2 -fomit-frame-pointer   -c -o conf.o conf.c
cc -Wall -Wmissing-prototypes -Wstrict-prototypes -O2 -fomit-frame-pointer   -c -o zconf.tab.o zconf.tab.c
cc   conf.o zconf.tab.o   -o conf

These lines aren't actually errors. The make command runs a bunch of other commands, as specified in a file called Makefile. By default, make will write out these commands to the terminal before running them. For example, if Makefile says to run foo then bar then baz, make will write foo to the terminal then run the foo command; then it will write bar to the terminal and run bar; then it will write baz to the terminal and run baz.

In this case, those cc lines are commands that make has been told to run by Makefile. The cc command will run the system's default C compiler, which is probably GCC. Those things beginning with - are options, which affect the behaviour of the C compiler.

For compilers like GCC, options beginning with -W tell the compiler to give out warnings when it sees code that's technically valid, but is often a bad idea (e.g. some pattern in the code which many programmers think will act in some way, but will actually act in another).

In this case -Wall turns on many (not quite all!) of GCC's warnings. -Wmissing-prototypes and -Wstrict-prototypes turn on extra warnings, to spot problems relating to C's function prototype feature.

Hence, these messages are really telling us that the cc command is about to be run, and that (among other things) it should warn us if it thinks the code is dodgy; in particular, if function prototypes are being misused.

GCC warnings look something like this:

main.c: In function ‘main’:
main.c:1:5: warning: traditional C rejects ISO C style function definitions [-Wtraditional]
 int main(int argc, char **argv) {
     ^

Since nothing like that appears in your output, no warnings or errors occurred; even with these extra -W checks enabled.