#include "panic.h"
#include "boot.h"
#include "util.h"
#include "pmap.h"
#include "pci.h"

enum {
  PCP_SELECT = 0x0cf8,
  PCP_READ   = 0x0cfc
};

uint16_t n_pci_devices;
static struct pci_device *pci_device_pages[256];

#define PCI_DEVICES_PER_PAGE (4096 / sizeof(struct pci_device))

struct pci_device *nth_pci_device(uint16_t n) {
  return pci_device_pages[n / PCI_DEVICES_PER_PAGE] + (n % PCI_DEVICES_PER_PAGE);
}

struct pci_device *find_pci_device_from_class_and_subclass(uint8_t class, uint8_t subclass, uint16_t start, uint16_t *index) {
  for (uint16_t n = start; n < n_pci_devices; ++n) {
    struct pci_device *p = nth_pci_device(n);
    if ((p->class == class) && (p->subclass == subclass)) {
      *index = n;
      return p;
    }
  }
  return 0;
}

static struct pci_device *next_pci_device() {
  if (!(n_pci_devices % PCI_DEVICES_PER_PAGE))
    if (!(pci_device_pages[n_pci_devices / PCI_DEVICES_PER_PAGE] = allocate_kernel_pages(1)))
      panic("Out of memory in PCI enumeration");
  return nth_pci_device(n_pci_devices++);
}

static uint32_t pci_read_config(uint16_t number, uint8_t reg) {
  uint32_t cspace_addr = 0x80000000 | (number << 8) | (reg << 2);
  outd(PCP_SELECT, cspace_addr);

  return ind(PCP_READ);
}

static void pci_device_check(uint16_t number) {
  uint32_t id = pci_read_config(number, 0);
  if ((id & 0xffff) == 0xffff)
    return;

  struct pci_device *next_device = next_pci_device();

  next_device->number = number;

  next_device->id_vendor = id;
  next_device->id_device = id >> 16;

  uint32_t class = pci_read_config(number, 2);

  next_device->class = class >> 24;
  next_device->subclass = class >> 16;
  next_device->iface = class >> 8;
}

void pci_init() {
  if (!(BOOT_INFO->support_flags & BIS_PCI))
    panic("No PCI support detected.");
  if (!(BOOT_INFO->pci_hw_char & PHC_CS_M1))
    panic("No PCI Mechanism 1 support");

  n_pci_devices = 0;

  for (uint32_t number = 0; number < (BOOT_INFO->last_pci_bus + 1) * 256; ++number)
    pci_device_check(number);
}