Disclaimer: I have never successfully used bridging.
Originally Posted by jemenake
However, I have a TiVo that needs two things:
1 - Connectivity to the internet to download program info
2 - Connectivity to the PC to play MP3's from it (via byRequest, which is a TiVo server kinda daemon).
This has to happen over a wired ethernet connection between the TiVo and the PC.
I think you can satisfy those requirements without a bridge, say, with IP masquerading.
1 - I've got an Atheros-style wireless card, with "wlan0" and "wmaster0". Am I correct to be using the "wlan0"?
Yes, this sounds right.
I'd run the wired network and hence eth0 on a different subnet (e.g., 192.168.3.0/24) than wlan0, and use NAT (network address translation). When TiVo sends a packet to "the internet" it goes by wire to your PC, which changes its source address to its own and forwards it through wlan0 to your ISP. When a response comes back, the PC undoes the NATting (masquerading) and passes the packet to TiVo. I think the easiest way to achieve that on a dynamically assigned address (as you get on wlan0 by DHCP) is masquerading -- man iptables
and look at target MASQUERADE.
If your TiVo sends DHCP requests, you can run a dhcpd (server) on your PC and satisfy them there. That's easy to set up, but make sure it only listens on eth0.