Problem

Can't get a  Kworld KW-TV878RF ( bt878 chipset ) to work, tvtime-scanner doesn't detect any channel, dmesg shows the module as loaded ( running the  2.6.28-6-generic kernel on Ubuntu 9.04 alpha , but that's not the issue as it turned out ), but still no channel available.

Solution

Edit /etc/modprobe.d/bttv and add the following lines:

alias char-major-81 videodev
alias char-major-81-0 bttv
options bttv card=78 tuner=5 radio=1

The first two lines might not be needed but that's how I had them on gentoo, before I decided to install ubuntu.
The last line is actually telling the bttv drive the exact type of card you have.
For other cards the card number might be different.