/*
 * irq.c
 *
 * Copyright (C) 2013 Aleksandar Andrejevic <theflash@sdf.lonestar.org>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <irq.h>
#include <heap.h>
#include <lock.h>
#include <cpu.h>

static list_entry_t irq_handlers[MAX_IRQ_COUNT];
static dword_t irq_alloc_bitmap = 0xFFFFF3FF;
static byte_t primary_pic_mask = 0xFF, secondary_pic_mask = 0xFF;

static void irq_handler(registers_t *regs, byte_t int_num)
{
    irq_handler_t *handler;
    byte_t irq_num = int_num - IRQ_INT_BASE;

    if (irq_num == 7)
    {
        cpu_write_port_byte(PRIMARY_PIC_CMD, 0x0B);

        byte_t isr = cpu_read_port_byte(PRIMARY_PIC_CMD);
        if (!(isr & 0x80)) return;
    }

    if (irq_num == 15)
    {
        cpu_write_port_byte(SECONDARY_PIC_CMD, 0x0B);

        byte_t isr = cpu_read_port_byte(SECONDARY_PIC_CMD);
        if (!(isr & 0x80))
        {
            cpu_write_port_byte(PRIMARY_PIC_CMD, 0x20);
            return;
        }
    }

    list_entry_t *ptr;
    for (ptr = irq_handlers[irq_num].next; ptr != &irq_handlers[irq_num]; ptr = ptr->next)
    {
        handler = CONTAINER_OF(ptr, irq_handler_t, list);

        cpu_enable_interrupts();
        handler->procedure(regs, irq_num);
        cpu_disable_interrupts();
    }

    if (irq_num >= 8) cpu_write_port_byte(SECONDARY_PIC_CMD, 0x20);
    cpu_write_port_byte(PRIMARY_PIC_CMD, 0x20);
}

dword_t register_irq_handler(byte_t irq_num, irq_handler_proc_t handler_proc, bool_t exclusive)
{
    dword_t ret = ERR_SUCCESS;
    critical_t critical;

    if (irq_num >= MAX_IRQ_COUNT) return ERR_INVALID;

    irq_handler_t *handler = (irq_handler_t*)malloc(sizeof(irq_handler_t));
    if (handler == NULL) return ERR_NOMEMORY;
    handler->procedure = handler_proc;
    handler->exclusive = exclusive;

    enter_critical(&critical);
    if (irq_handlers[irq_num].next == &irq_handlers[irq_num])
    {
        if (irq_num >= 0 && irq_num < 8)
        {
            primary_pic_mask &= ~(1 << irq_num);
            cpu_write_port_byte(PRIMARY_PIC_DATA, primary_pic_mask);
        }
        else
        {
            secondary_pic_mask &= ~(1 << (irq_num - 8));
            cpu_write_port_byte(SECONDARY_PIC_DATA, secondary_pic_mask);
        }
    }
    else if (exclusive || CONTAINER_OF(irq_handlers[irq_num].next, irq_handler_t, list)->exclusive)
    {
        ret = ERR_EXISTS;
    }

    if (ret == ERR_SUCCESS) list_append(&irq_handlers[irq_num], &handler->list);
    leave_critical(&critical);

    return ret;
}

dword_t unregister_irq_handler(byte_t irq_num, irq_handler_proc_t handler_proc)
{
    bool_t found = FALSE;
    critical_t critical;

    if (irq_num >= MAX_IRQ_COUNT) return ERR_INVALID;
    enter_critical(&critical);
    list_entry_t *ptr;

    for (ptr = irq_handlers[irq_num].next; ptr != &irq_handlers[irq_num]; ptr = ptr->next)
    {
        irq_handler_t *handler = CONTAINER_OF(ptr, irq_handler_t, list);
        if (handler->procedure == handler_proc)
        {
            list_remove(&handler->list);
            free(handler);
            found = TRUE;

            break;
        }
    }

    leave_critical(&critical);
    return found ? ERR_SUCCESS : ERR_NOTFOUND;
}

byte_t alloc_irq()
{
    byte_t i;

    for (i = 0; i < MAX_IRQ_COUNT; i++) if (!test_bit(&irq_alloc_bitmap, i))
    {
        set_bit(&irq_alloc_bitmap, i);
        return i;
    }

    return 0xFF;
}

void free_irq(byte_t number)
{
    clear_bit(&irq_alloc_bitmap, number);
}

void irq_init()
{
    byte_t i;

    primary_pic_mask &= ~(1 << PRIMARY_PIC_CASCADE_IRQ);
    cpu_write_port_byte(PRIMARY_PIC_CMD, 0x11);
    cpu_write_port_byte(SECONDARY_PIC_CMD, 0x11);
    cpu_write_port_byte(PRIMARY_PIC_DATA, PRIMARY_IRQ_INT);
    cpu_write_port_byte(SECONDARY_PIC_DATA, SECONDARY_IRQ_INT);
    cpu_write_port_byte(PRIMARY_PIC_DATA, 1 << PRIMARY_PIC_CASCADE_IRQ);
    cpu_write_port_byte(SECONDARY_PIC_DATA, 1 << SECONDARY_PIC_CASCADE_IRQ);
    cpu_write_port_byte(PRIMARY_PIC_DATA, PIC_8086_MODE);
    cpu_write_port_byte(SECONDARY_PIC_DATA, PIC_8086_MODE);
    cpu_write_port_byte(PRIMARY_PIC_DATA, primary_pic_mask);
    cpu_write_port_byte(SECONDARY_PIC_DATA, secondary_pic_mask);

    for (i = 0; i < MAX_IRQ_COUNT; i++)
    {
        list_init(&irq_handlers[i]);
        set_int_handler(IRQ_INT_BASE + i, irq_handler, FALSE, FALSE);
    }
}