For iPods formatted HFS+, it requires the kernel to support the Mac partitioning scheme. This adds a very small amount of code and data, but it can't be done with a module. One big plus is it allows >4G files.

Does anyone know if Diablo will have Mac Partition support in the kernel so I won't have to reflash? Even if it doesn't do hfsplus in the kernel, I can add that and the rest as kernel modules without reflashing. I CAN mount my HFS+ formatted iPod, but it requires a program to find the offset of the partition into the drive and a loopback device.

/dev/sda3 would be much easier.

I highly doubt it. That's pretty far out of the intended use, unless SDs are commonly found with mac partition tables. But a kernel could be recompiled with that, and I suppose you could put it in bugzilla...