The following ordered list defines different classes of hardware
according to the freedom they provide to the user.  One should reject
hardware in a lower class if there is hardware available in a higher
class that will do the same job.

1. Hardware whose design is freely licensed (e.g. ORPSoC, lowRISC)
2. Hardware with documentation enabling the user to write firmware
3. Hardware with freely licensed firmware (e.g. ath9k)
4. Hardware with proprietary firmware (e.g. AMD Radeon)
5. Hardware with proprietary firmware and proprietary userspace (e.g. PowerVR)
6. Hardware with proprietary firmware and proprietary drivers
   (e.g. Highpoint Rocket 1540 SATA controller)
7. Hardware with proprietary firmware, proprietary drivers and
   proprietary userspace (e.g. Broadcom BCM4751 GPS chip)
8. Hardware that only accepts firmware which is cryptographically
   signed by entities other than the user (e.g. Nvidia GPUs from
   Maxwell GM200 onwards)