Function vmem_fit

freebsd/kern/subr_vmem.c:945–990

* vmem_fit: check if a bt can satisfy the given restrictions. * * it's a caller's responsibility to ensure the region is big enough * before calling us. */

 * before calling us.
 */
static int
vmem_fit(const bt_t *bt, vmem_size_t size, vmem_size_t align,
    vmem_size_t phase, vmem_size_t nocross, vmem_addr_t minaddr,
    vmem_addr_t maxaddr, vmem_addr_t *addrp)
{
	vmem_addr_t start;
	vmem_addr_t end;

	MPASS(size > 0);
	MPASS(bt->bt_size >= size); /* caller's responsibility */

	/*
	 * XXX assumption: vmem_addr_t and vmem_size_t are
	 * unsigned integer of the same size.
	 */

	start = bt->bt_start;
	if (start < minaddr) {
		start = minaddr;
	}
	end = BT_END(bt);
	if (end > maxaddr)
		end = maxaddr;
	if (start > end) 
		return (ENOMEM);

	start = VMEM_ALIGNUP(start - phase, align) + phase;
	if (start < bt->bt_start)
		start += align;
	if (VMEM_CROSS_P(start, start + size - 1, nocross)) {
		MPASS(align < nocross);
		start = VMEM_ALIGNUP(start - phase, nocross) + phase;
	}
	if (start <= end && end - start >= size - 1) {
		MPASS((start & (align - 1)) == phase);
		MPASS(!VMEM_CROSS_P(start, start + size - 1, nocross));
		MPASS(minaddr <= start);
		MPASS(maxaddr == 0 || start + size - 1 <= maxaddr);
		MPASS(bt->bt_start <= start);
		MPASS(BT_END(bt) - start >= size - 1);
		*addrp = start;

		return (0);
	}
	return (ENOMEM);
}

/*
 * vmem_clip:  Trim the boundary tag edges to the requested start and size.