#include <atags.h>

extern uint32 atags_ptr;

int atag_valid(struct atag *a) {
	switch (a->tag) {
		case ATAG_NONE:
			return a->size == 2;
		case ATAG_CORE:
			return a->size == 2 || a->size == 5;
		case ATAG_MEM:
		case ATAG_INITRD2:
		case ATAG_SERIAL:
			return a->size == 4;
		case ATAG_VIDEOTEXT:
		case ATAG_RAMDISK:
			return a->size == 5;
		case ATAG_REVISION:
			return a->size == 3;
		case ATAG_VIDEOLFB:
			return a->size == 8;
		case ATAG_CMDLINE:
			return a->size >= 3;
		default:
			return 0;
	}
}

int _atags_mem_region(struct atag **mem_header, int initialize) {
	if (initialize)
		*mem_header = (struct atag *)atags_ptr;
	else
		*mem_header = (struct atag *)((uint32 *)*mem_header + (*mem_header)->size);

	while (atag_valid(*mem_header) && (*mem_header)->tag != ATAG_NONE && (*mem_header)->tag != ATAG_MEM) {
		*mem_header = (struct atag *)((uint32 *)*mem_header + (*mem_header)->size);
	}

	if (!atag_valid(*mem_header) || (*mem_header)->tag == ATAG_NONE)
		return -1;
	return 0;
}