Support for userspace drivers

[farlepet]

Requirements:

• Syscall to read/write ports (x86)
  • Potentially syscall to request access to specific ports, so a faulty driver that attempts to access a port it hasn't requested, it can be terminated
• Memory mapping syscall
• Registering and handling interrupts from userspace
  • Potentially by having a thread for each interrupt source, and blocking until the kernel messages it that an interrupt has been received
  • Threads waiting on an interrupt could also potentially be re-prioritized on interrupt reception, and the scheduler called
  • Registering a callback with the kernel would be more efficient, but would sacrifice some of the security/stability concerns of moving drivers to userspace
    • Inefficient drivers whose interrupts fire often can bog down the system
    • If drivers are run in kernel mode, they have greater access to the system