I have been trying for about 6 hours to get the lirc_serial kernel module to
compile. I tried the source that came with knoppmyth first, then I tried the
latest release from CVS. Both suffer from the same problem. After
the sh autogen.sh and the sh setup.sh and finally at the make command I get
the error that says no rule to make Rules.make. I looked into the Makefile
in the /usr/src/kernel-headers-2.4.25-chw/Makefile and found a reference to Rules.make. It said to put 'kbuild_2_4_nostdinc :=' before the include Rules.make. I tried this and the second suggestion to add a -I/usr/include
in the include dirs. But the problem is that there is no file Rules.make anywhere on the whole hard drive. So there is never going to be a path that works. Does anyone have a suitable "Rules.make" file to go with the
knoppmyth system (kernel-2.4.25-chw)? Or has anyone found a way around this bug in compiling lirc_serial.o kernel module. The lirc-0.6.6 version compiles, but I don't know if it is compatible with the other peices that come
with knoppmyth. Has anyone replaced all of the peices ie the whold lirc-0.6.6 release to see if it works with knoppmyth?

I solved it. The source directory /usr/src/linux is erroneously linked symbolically to a subtree that does not contain the kernel source. Just a few headerfiles. delete this symbolic link and unzip the real source tree in
/usr/src/kernel-2.4.25-chw.tar.bz2 then relink the symbolic link to the newly created complete kernel source tree and the compile will work just fine.
cd /usr/src
rm linux
tar -xjf kernel-2.5.25-chw.tar.bz2
ln -s kernel-2.4.25-chw linux

Then cd lirc and do the make

Barry, you just saved me a ton of work! I was lucky enough to find this post when I ran into the same problem trying to install a second instance of lirc to get my IRBlaster working, according to the instructions at

http://members.cox.net/rwraithr/IRBlaster_Howto.txt

Anyway, I think you have some typos in your instructions. Here's what worked for me:

cd /usr/src
rm linux
tar -xjf linux-2.4.25-chw.tar.bz2 # change 'kernel' to 'linux' and first 5 to 4
ln -s linux-2.4.25-chw linux # change 'kernel' to 'linux'

Thanks!