#include <oskit/x86/pio.h>
These are macros for accessing IO-space directly on the x86. These instructions will generate traps if executed in user-mode without permissions (either IOPL in the eflags register or access via the io-bitmap in the tss).
- iodelay()
- A macro used to delay the processor for a short period of time, generally to wait until programmed io can complete. The actual amount of time is indeterminate, since the delay is accomplished by doing an inb from a nonexistent port, which depends on the processor and chipset.
The nominal delay value is 1uS for most machines.
- inl(port)
- Returns 32-bit value from port
- inw(port)
- Returns 16-bit value from port
- inb(port)
- Returns 8-bit value from port
- inl_p(port)
- inl followed immediately by iodelay
- inw_p(port)
- inw followed immediately by iodelay
- inb_p(port)
- inb followed immediately by iodelay
- outl(port, val)
- Send 32-bit val out port.
- outw(port, val)
- Send 16-bit val out port.
- outb(port, val)
- Send 8-bit val out port.
- outl_p(port)
- outl followed immediately by iodelay
- outw_p(port)
- outw followed immediately by iodelay
- outb_p(port)
- outb followed immediately by iodelay
The above macros have versions that begin with i16_, which are defined to be the same. It may be desirable to use the i16_ versions in 16-bit code in place of the normal macros for clarity.
This header file is taken from CMU's Mach kernel.