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LCA: Andrew Tanenbaum on creating reliable systems
LCA: Andrew Tanenbaum on creating reliable systems
Posted Jan 18, 2007 22:42 UTC (Thu) by nix (subscriber, #2304)In reply to: LCA: Andrew Tanenbaum on creating reliable systems by jamesh
Parent article: LCA: Andrew Tanenbaum on creating reliable systems
So Minix I/O port access always involves at least two ring transitions
*per port I/O*?
Given the timing-sensitive nature of much port I/O that strikes me as both
wildly impractical and somewhat dangerous.
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LCA: Andrew Tanenbaum on creating reliable systems
Posted Jan 24, 2007 14:01 UTC (Wed) by kleptog (subscriber, #1183) [Link]
On i386 hardware, it's possible to grant an unprivelidged processes access to particular I/O ports, without having to do any ring transitions. On Linux it's the ioperm() function call.
These days people use memory-mapped I/O so mmap() is what you mostly need.
LCA: Andrew Tanenbaum on creating reliable systems
Posted Feb 2, 2007 13:46 UTC (Fri) by willy (subscriber, #9762) [Link]
Yes, but minix explicitly doesn't do ioperm, it really does call down to the microkernel to do IO port accesses. He talked about how 'evil' mmaped IO was.