1. 根目录:
2. arch
3. x86
4. include
5. asm
6. i8253.h

#ifndef _ASM_X86_I8253_H
#define _ASM_X86_I8253_H

/* i8253A PIT registers */
#define PIT_MODE		0x43
#define PIT_CH0			0x40
#define PIT_CH2			0x42

extern raw_spinlock_t i8253_lock;

extern struct clock_event_device *global_clock_event;

extern void setup_pit_timer(void);

#define inb_pit		inb_p
#define outb_pit	outb_p

#endif /* _ASM_X86_I8253_H */