126 lines
3.9 KiB
C
126 lines
3.9 KiB
C
#include <system.h>
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/* These are own ISRs that point to our special IRQ handler
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* instead of the regular 'fault_handler' function */
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extern void irq0();
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extern void irq1();
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extern void irq2();
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extern void irq3();
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extern void irq4();
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extern void irq5();
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extern void irq6();
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extern void irq7();
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extern void irq8();
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extern void irq9();
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extern void irq10();
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extern void irq11();
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extern void irq12();
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extern void irq13();
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extern void irq14();
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extern void irq15();
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/* This array is actually an array of function pointers. We use
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* this to handle custom IRQ handlers for a given IRQ */
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void *irq_routines[16] =
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{
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0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0
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};
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/* This installs a custom IRQ handler for the given IRQ */
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void irq_install_handler (int irq, void (*handler)(regs *r))
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{
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irq_routines[irq] = handler;
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}
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void irq_uninstall_handler (int irq)
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{
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irq_routines[irq] = 0;
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}
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/* Normally, IRQs 0 to 7 are mapped to entries 8 to 15. This
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* is a problem in protected mode, because IDT entry 8 is a
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* Double Fault! Without remapping, every time IRQ0 fires,
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* you get a Double Fault Exception, which is NOT actually
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* what's happening. We send commands to the Programmable
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* Interrupt Controller (PICs - also called the 8259's) in
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* order to make IRQ0 to 15 be remapped to IDT entries 32 to
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* 47 */
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void irq_remap(int pic1, int pic2)
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{
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// Send ICW1
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outportb(0x20, 0x11);
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outportb(0xA0, 0x11);
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// send ICW2
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outportb(0x21, pic1); // remap pics
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outportb(0xA1, pic2);
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// send ICW3
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outportb(0x21, 4);
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outportb(0xA1, 2);
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// Send ICW4
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outportb(0x21, 0x01);
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outportb(0xA1, 0x01);
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outportb(0x21, 0x00);
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}
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/* We first remap the interrupt controllers, and then we install
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* the appropriate ISRs to the correct entries in the IDT. This
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* is just like installing the exception handlers */
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void irq_install()
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{
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irq_remap(32,40);
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idt_set_gate(32, (unsigned)irq0, 0x08, 0x8E);
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idt_set_gate(33, (unsigned)irq1, 0x08, 0x8E);
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idt_set_gate(34, (unsigned)irq2, 0x08, 0x8E);
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idt_set_gate(35, (unsigned)irq3, 0x08, 0x8E);
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idt_set_gate(36, (unsigned)irq4, 0x08, 0x8E);
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idt_set_gate(37, (unsigned)irq5, 0x08, 0x8E);
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idt_set_gate(38, (unsigned)irq6, 0x08, 0x8E);
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idt_set_gate(39, (unsigned)irq7, 0x08, 0x8E);
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idt_set_gate(40, (unsigned)irq8, 0x08, 0x8E);
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idt_set_gate(41, (unsigned)irq9, 0x08, 0x8E);
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idt_set_gate(42, (unsigned)irq10, 0x08, 0x8E);
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idt_set_gate(43, (unsigned)irq11, 0x08, 0x8E);
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idt_set_gate(44, (unsigned)irq12, 0x08, 0x8E);
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idt_set_gate(45, (unsigned)irq13, 0x08, 0x8E);
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idt_set_gate(46, (unsigned)irq14, 0x08, 0x8E);
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idt_set_gate(47, (unsigned)irq15, 0x08, 0x8E);
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}
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/* Each of the IRQ ISRs point to this function, rather than
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* the 'fault_handler' in 'isrs.c'. The IRQ Controllers need
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* to be told when you are done servicing them, so you need
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* to send them an "End of Interrupt" command (0x20). There
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* are two 8259 chips: The first exists at 0x20, the second
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* exists at 0xA0. If the second controller (an IRQ from 8 to
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* 15) gets an interrupt, you need to acknowledge the
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* interrupt at BOTH controllers, otherwise, you only send
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* an EOI command to the first controller. If you don't send
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* an EOI, you won't raise any more IRQs */
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void irq_handler (regs *r)
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{
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/* This is a blank function pointer */
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void (*handler)(regs *r);
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/* Find out if we have a custom handler to run for this
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* IRQ, and then finally, run it */
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handler = irq_routines[r->int_no - 32];
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if (handler) handler(r);
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/* If the IDT entry that was invoked was greater than 40
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* (meaning IRQ8 - 15), then we need to send an EOI to
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* the slave controller */
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if (r->int_no >=40) outportb(0x0A, 0x20);
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/* In either case, we need to send an EOI to the master
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* interrupt controller too */
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outportb(0x20, 0x20);
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}
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