Function cdev_pager_allocate

freebsd/vm/device_pager.c:126–219

}

vm_object_t
cdev_pager_allocate(void *handle, enum obj_type tp, struct cdev_pager_ops *ops,
    vm_ooffset_t size, vm_prot_t prot, vm_ooffset_t foff, struct ucred *cred)
{
	vm_object_t object, object1;
	vm_pindex_t pindex;
	u_short color;

	if (tp != OBJT_DEVICE && tp != OBJT_MGTDEVICE)
		return (NULL);
	KASSERT(tp == OBJT_MGTDEVICE || ops->cdev_pg_populate == NULL,
	    ("populate on unmanaged device pager"));

	/*
	 * Offset should be page aligned.
	 */
	if (foff & PAGE_MASK)
		return (NULL);

	/*
	 * Treat the mmap(2) file offset as an unsigned value for a
	 * device mapping.  This, in effect, allows a user to pass all
	 * possible off_t values as the mapping cookie to the driver.  At
	 * this point, we know that both foff and size are a multiple
	 * of the page size.  Do a check to avoid wrap.
	 */
	size = round_page(size);
	pindex = OFF_TO_IDX(foff) + OFF_TO_IDX(size);
	if (pindex > OBJ_MAX_SIZE || pindex < OFF_TO_IDX(foff) ||
	    pindex < OFF_TO_IDX(size))
		return (NULL);

	if (ops->cdev_pg_ctor(handle, size, prot, foff, cred, &color) != 0)
		return (NULL);
	mtx_lock(&dev_pager_mtx);

	/*
	 * Look up pager, creating as necessary.
	 */
	object1 = NULL;
	object = vm_pager_object_lookup(&dev_pager_object_list, handle);
	if (object == NULL) {
		/*
		 * Allocate object and associate it with the pager.  Initialize
		 * the object's pg_color based upon the physical address of the
		 * device's memory.
		 */
		mtx_unlock(&dev_pager_mtx);
		object1 = vm_object_allocate(tp, pindex);
		object1->flags |= OBJ_COLORED;
		object1->pg_color = color;
		object1->handle = handle;
		object1->un_pager.devp.ops = ops;
		object1->un_pager.devp.dev = handle;
		TAILQ_INIT(&object1->un_pager.devp.devp_pglist);
		mtx_lock(&dev_pager_mtx);
		object = vm_pager_object_lookup(&dev_pager_object_list, handle);
		if (object != NULL) {