USB HID chip similar to FTDI
One alternative to the FTDI SPI-to-USB chips is the MCP2210 IC from Microchip.


  The MCP2210 device is a USB-to-SPI Master converter which enables USB
  connectivity in applications that have an SPI interface. The device
  reduces external components by integrating the USB termination
  resistors. The MCP2210 also has 256 bytes of integrated user EEPROM.
  The MCP2210 has nine general purpose input/output pins. Seven pins
  have alternate functions to indicate USB and communication status.
  
  Universal Serial Bus (USB)
  
  
  Supports full-speed USB (12 Mb/s)
  Human Interface Device (HID) device
  128-byte Buffer to handle data throughput
  Fully configurable VID, PID assignments and string descriptors
  Bus powered (factory default) or self-powered (can be selected    through special USB commands)
  USB 2.0 Compliant
  
  
  USB Driver and Software Support
  
  
  Uses standard HID drivers (built-in support on Windows® XP, Vista, 7,    Linux and Mac OS®)
  Configuration utility for device’s power-up configuration
  Utility for USB-SPI communication, GPIO manipulation and    miscellaneous features usage
  
  
  SPI Master peripheral
  
  
  Supports all four SPI modes (Mode 0, 1, 2, 3)
  Bit-rates from 1500 bps up to 12 Mbps
  Configurable delays for SPI transactions
  SPI transactions lengths of up to 65535 bytes long
  Up to 9 Chip Select lines – to be used in any combination for a given    SPI transaction (the chip select lines are shared between
  GPIOs and    alternate function pins; certain GPs – up to 9 of them –
  can be    assigned with the chip select functionality)
  
  
  General Purpose Input/Output (GPIO) Pins
  
  
  Nine general purpose I/O pins
  
  
  EEPROM
  
  
  256 bytes of user EEPROM (accessible only through certain USB commands)
  


Excerpt from the datasheet regarding the HID enumeration:


  
  ENUMERATION
  
  
  The MCP2210 will enumerate as a USB device after Power-on Reset (POR).
  The device enumerates as a Human Interface Device (HID) only.
  
  
  Human Interface Device (HID)
  
  
  The MCP2210 enumerates as an HID, so the device can be configured and
  all the other functionalities can be controlled. A DLL package that
  facilitates I/O control through a custom interface is supplied by
  Microchip and is available on the product landing page.