chk_dev
static DEVT *chk_dev(dev_t, int);
if (chk_dev(arcn->sb.st_dev, 1) == NULL)
if ((pt = chk_dev(arcn->sb.st_dev, 0)) != NULL) {
if ((pt = chk_dev(arcn->sb.st_dev, 1)) == NULL)
if (chk_dev(lastdev, 0) != NULL)
(chk_dev(lastdev, 1) == NULL))