As I was trying to setup phc-intel on my MacBook Air (Intel Core2Duo P7500 processor), running Linux Mint 6 (based upon Ubuntu 8.10, itself based upon kernel 2.6.27) I stumbled across a little problem.
I first tried to download phc-intel-0.3.2-3.tar.gz [18.54 KiB] from the download page . Problem is: two files are required in order to patch, acpi_cpufreq.c and linux-phc-0.3.2.patch. These files are available in inc/ ; in two separate folders : one for kernel 2.6.28, and one for 2.6.29.
Sooo I continued to read the download page, and found a patch file for kernel 2.6.26 which was supposed to work with kernel 2.6.27. So I downloaded it and copied it into my newly created inc/2.6.27 folder, copied acpi_cpufreq.c from kernel 2.6.28, and rebooted. Rock on!
Despite one or two compilation warnings, it seemed to work right.
Though... Boot freezed a bit after acpi launch, at:
Only workaround I found was to reboot from an external drive and comment out the lines at /etc/modprobe/phc-intel.conf . I could boot again, but without any phc-intel.CPUFreq Utilities : Setting ondemand CPUFreq governor...
After some research, and various attempts to "make prepare && make && sudo make install", I started to think about this acpi_cpufreq.c file I used... It might have changed between kernel 2.6.27 and 2.6.28 ("diff" confirms modifications have been made between 2.6.28 and 2.6.29), so I downloaded the 2.6.27 version from kernel.org (here is the exact link) into my inc/2.6.27 folder.
make prepare ; make ; sudo make install... No error, reboot is okay, it works! lsmod confirms.
I hope it might help others having similar problems.