It seems that "struct i2c_client" has changed in newer kernels, causing the current build of ivtv to fail as it uses a now non-existant field.
This a problem upstream, they are aware of it, they haven't fixed it.
ivtv-0.2.0-rc3k has been released and contains the fix for the i2c id problem. I used portage overlay to test with 2.6.12-ck2 and it compiles successfully. rc3k is locate at Chris Kennedy's site: http://www.ivtv.tv/releases/ivtv-0.2/ivtv-0.2.0-rc3k.tgz