Hello! After upgrading to 12.2 and the kernel to new one i got an interesting issue. With boot up there is not an rtc probe, nor in /proc the rtc exist. I have a line in rc.local pleced there for mplayer: "echo 1024 > /proc/sys/dev/rtc/max-user-freq", which return something like "not such file or directory" and does not creates that.
This issue occures with generic-smp-2.6.27.7 kernel (recommended), as well as with self compiled 2.6.27.8 and 2.6.27.9 compiled by generic-smp config with minor changes.
rtc compiled as modules in the kernel are not loaded in boot time. "modprobe rtc-core" doesn't create /proc/sys/dev/rtc/.
The old kernel - 2.6.24.7 self compiled (by generic-smp-2.6.24.4) works well and with no problems in 12.2. The only issue with 12.1 was a boot worrning about rtc-core error, may be something about the hardware, but i had rtc loaded and this settings in /proc (well with the old kernel the mashine makes more noise then with some of the 2.6.27.*)
Is it a normal change in the 2.6.27.* kernels, replaceing rtc/max-user-freq with another function or there is a problem with them.

Try creating the file in /proc with "touch" before "echo"ing to it - it shouldn't need to be, but just to play it safe:

Well, i found it! The new kernel exports that in /sys/class/rtc/rtc0/max-user-freq" But, as rtc are campiled as modules, rtc-cmos module must be loaded, it shoudn't be loaded automatically.
rc.modules: modprobe rtc-cmos
rc.local: echo 1024 > /sys/class/rtc/rtc0/max-user-freq
However mplayer gurus suggest it is needed only in old mashines.
It was strange to me, the 2.6.24.7 kernel has option CONFIG_RTC, loads every rtc modules and exports rtc/max-user-freq anywhere, but the new 2.6.27.* doesn't have that option. Modprobe rtc-core doesn't loads rtc-cmos and doesn't exports that in /sys.

Until udev 132 the rtc-core module was loaded at boot time. With udev 133 it does not load it anymore and you have to load the rtc-cmos manually or add to rc.modules, like you noticed longus