In both ways the BUG is not hit, and the TV-card puts things to screen. Adding a printk in the bttv-source could change the behavior and also changing the verbose and debug options in conf.modules. But what the bttv code does I have only a very general idea. Thus i have highmem and in my understanding it is in the pci-dma accessable address range. Also the DMA-transfer to screen goes to 0xE2000000 at my setup.
Tools are in the right versions.