mirror of
https://github.com/Plexi09/Nadir-Kernel.git
synced 2026-10-20 15:07:27 +02:00
90 lines
2.2 KiB
C
90 lines
2.2 KiB
C
/* Nadir 8259 PIC driver: cascaded master/slave remap + EOI + masking.
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*
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* Runs in 64-bit long mode at Ring 0 (CPL 0) with the stage-2 GDT.
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* Privileged instructions: `outb`/`inb` via io.h (trap #GP if CPL >
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* IOPL); no `cli`/`sti`/`lidt`.
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* Fault behavior: no CPU fault possible a wrong ICW order only
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* misroutes IRQs.
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*/
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#include <stdint.h>
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#include "io.h"
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#include "pic.h"
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/* Init control words: ICW1 starts init, ICW2 sets the vector base,
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* ICW3 wires the cascade (master IRQ2 <-> slave identity 2), ICW4
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* selects 8086 mode. io_wait() after each byte gives the slow 8259
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* time to latch it. */
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#define PIC_ICW1_INIT 0x11U
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#define PIC_ICW3_MASTER_SLAVE_LINE 0x04U
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#define PIC_ICW3_SLAVE_ID 0x02U
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#define PIC_ICW4_8086 0x01U
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void pic_remap(void)
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{
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/* WHY this exact order: the 8259 latches ICW2-4 only while in init
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* mode, and the cascade identities must match or slave IRQs never
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* reach the CPU. Mask-all at the end keeps devices quiet until
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* their driver calls pic_unmask(). */
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outb(PIC1_CMD, PIC_ICW1_INIT);
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io_wait();
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outb(PIC2_CMD, PIC_ICW1_INIT);
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io_wait();
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outb(PIC1_DATA, PIC_IRQ0_VECTOR);
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io_wait();
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outb(PIC2_DATA, PIC_IRQ8_VECTOR);
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io_wait();
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outb(PIC1_DATA, PIC_ICW3_MASTER_SLAVE_LINE);
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io_wait();
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outb(PIC2_DATA, PIC_ICW3_SLAVE_ID);
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io_wait();
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outb(PIC1_DATA, PIC_ICW4_8086);
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io_wait();
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outb(PIC2_DATA, PIC_ICW4_8086);
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io_wait();
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outb(PIC1_DATA, 0xFFU);
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io_wait();
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outb(PIC2_DATA, 0xFFU);
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io_wait();
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}
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void pic_eoi(uint8_t irq)
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{
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if (irq >= PIC_IRQ_COUNT) {
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return;
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}
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if (irq >= 8U) {
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outb(PIC2_CMD, PIC_EOI);
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}
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outb(PIC1_CMD, PIC_EOI);
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}
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void pic_mask(uint8_t irq)
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{
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uint16_t port;
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uint8_t mask;
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if (irq >= PIC_IRQ_COUNT) {
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return;
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}
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port = (irq < 8U) ? PIC1_DATA : PIC2_DATA;
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mask = inb(port) | (uint8_t)(1U << (irq & 7U));
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outb(port, mask);
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}
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void pic_unmask(uint8_t irq)
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{
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uint16_t port;
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uint8_t mask;
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if (irq >= PIC_IRQ_COUNT) {
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return;
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}
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port = (irq < 8U) ? PIC1_DATA : PIC2_DATA;
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mask = inb(port) & (uint8_t) ~(1U << (irq & 7U));
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outb(port, mask);
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}
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