The devb-umass driver supports devices that follow the Mass Storage Class Specification.
You can determine that the device is suitable by looking for the following information in the output from usb -vv:
Mass Storage Class 08h SubClass Code Command Block Specification 01h Reduced Block Command (RBC) 02h SFF-8020i, MMC-2 (ATAPI) 04h UFI 05h SFF-8070i 06h SCSI transparent Protocol Code Protocol Implementation 00h Control/Bulk/Interrupt (with command completion interrupt) 01h Control/Bulk/Interrupt (with no command completion interrupt) 50h Bulk-Only Transport
To use a USB mass-storage device on a Neutrino system, start io-usb as described above, then the devb-umass driver. By default, this driver creates an entry for disk-based devices in /dev in the form /dev/hdn, where n is the drive number. Once you've started the driver, you can treat the device like a disk.
For example, for a mass-storage device that uses the UHCI controller, type:
io-usb -d uhci devb-umass cam pnp