#include <endian.h>
#include <log.h>
#include <stdbool.h>
#include <stdint.h>

#define ARM_DTB_PTR32 0x000000f8

struct __attribute__((packed)) header {
  uint32_t magic;
#define DTB_MAGIC 0xd00dfeed
  uint32_t total_size;
#define DTB_MAX_SIZE 0x100000
  uint32_t off_dt_strt;
  uint32_t off_dt_strs;
  uint32_t off_mem_rsvmap;
  uint32_t version;
#define DTB_VERSION 17
  uint32_t last_comp_version;
#define DTB_LAST_COMP_VERSION 16
  uint32_t boot_cpuid_phys;
  uint32_t size_dt_strs;
  uint32_t size_dt_strt;
};

static const struct header *hdr = 0;

bool gilbraltar_dtb_init(void) {
  uint32_t *volatile ptr = (uint32_t *volatile)ARM_DTB_PTR32;

  const void *dtb = (const void *)(uintptr_t)*ptr;
  hdr = (const struct header *)dtb;

  if (be32toh(hdr->magic) != DTB_MAGIC ||
      be32toh(hdr->last_comp_version) != DTB_LAST_COMP_VERSION)
    return false;

  uint32_t total_size = be32toh(hdr->total_size);

  if (total_size < sizeof(struct header) || total_size > DTB_MAX_SIZE)
    return false;

  return true;
}