/*
  StarForth — Steady-State Virtual Machine Runtime
  Copyright (c) 2023–2025 Robert A. James. All rights reserved.
  Licensed under the StarForth License, Version 1.0.
 */

/**
 * plic.h - Platform-Level Interrupt Controller interface (riscv64 only)
 *
 * Item 4.3.5a (FABRIC.md §27.5): Phase 0 (0.2/0.3) only ever enabled the
 * S-mode *timer* interrupt (sie.STIE). External interrupts (sie.SEIE) were
 * never touched, and the PLIC -- the only external-interrupt path on
 * RISC-V, there is no legacy PIC or I/O APIC equivalent -- had no driver
 * at all before this item. Pure substrate: this item wires the mechanism
 * (claim/dispatch/complete) with no permanent source enabled by default;
 * a real consumer (4.3.5b, virtio-keyboard) enables its own source later.
 */

#ifndef STARKERNEL_PLIC_H
#define STARKERNEL_PLIC_H

#include <stdint.h>

/**
 * Map the PLIC and set the S-mode hart-0 context's priority threshold to 0
 * (maximally permissive -- safe because nothing is enabled at any source
 * by default; enabling a source is what actually lets it reach claim()).
 * Also sets sie.SEIE. Does not touch sstatus.SIE -- arch_enable_interrupts()
 * still owns that, same as the timer.
 *
 * @return 0 on success.
 */
int plic_init(void);

/** Set a source's interrupt priority (1-7; 0 means "never interrupt"). */
void plic_set_priority(uint32_t irq, uint32_t priority);

/** Enable a source for the S-mode hart-0 context. */
void plic_enable(uint32_t irq);

/** Disable a source for the S-mode hart-0 context. */
void plic_disable(uint32_t irq);

/**
 * Claim the highest-priority pending interrupt for the S-mode hart-0
 * context. Returns the source ID, or 0 if none is pending.
 */
uint32_t plic_claim(void);

/** Signal completion of the source previously returned by plic_claim(). */
void plic_complete(uint32_t irq);

#endif /* STARKERNEL_PLIC_H */