can't mount usb hd, /dev/sda4 does not exist

[Tamas K Papp <tpapp@Princeton.EDU>]

I am trying to use an external usb hd with a custom kernel (I need the
custom kernel because of the suspend2 patch).  With the stock debian
kernel (2.6.15-1-486), it works fine and mounts on /dev/sda4.

With my custom kernel, it gives the error message:

mount: special device /dev/sda4 does not exist

The lsusb line for the device is:

Bus 005 Device 004: ID 0dc4:0073 Macpower Peripherals, Ltd

What driver is missing from my kernel?  Other usb devices (eg
pendrives, digital cameras, mp3 players) mount fine.

Thanks,

Tamas