When running "zpool import -d /dev", this command should loop on all devices in /dev and try to open them to look for a zpool. Unfortunately there is a small programming error in the way the name of the device is computed, as shown with ktrace:

 16061 zpool    CALL  open(0xbfbfa724,O_RDONLY,<unused>0x280cdaef)
 16061 zpool    NAMI  "/dev//geom.ctl"
 16061 zpool    CALL  open(0xbfbfa724,O_RDONLY,<unused>0x280cdaef)
 16061 zpool    NAMI  "/dev//geom.ctl/console"
 16061 zpool    RET   open -1 errno 20 Not a directory
 16061 zpool    CALL  open(0xbfbfa724,O_RDONLY,<unused>0x280cdaef)
 16061 zpool    NAMI  "/dev//geom.ctl/console/devctl"

[...]

 16061 zpool    CALL  open(0xbfbfa724,O_RDONLY,<unused>0x280cdaef)
 16061 zpool    NAMI  "/dev//geom.ctl/console/devctl/null/zero/klog/pci/ptmx/ctty/random/urandom/bpf/bpf0/sysmouse/dcons/dgdb/fido/nfslock/audit/fd/stdin/stdout/stderr/io/kbdmux0/kbd1/mem/kmem/ata/acpi/led/atkbd0/kbd0/psm0/bpsm0/lpt0/lpt0.ctl/ppi0/ttyu0/ttyu0.init/ttyu0.lock/cuau0/cuau0.init/cuau0.lock/ttyv0/ttyv1/ttyv2/ttyv3/ttyv4/ttyv5/ttyv6/ttyv7/ttyv8/ttyv9/ttyva/ttyvb/ttyvc/ttyvd/ttyve/ttyvf/consolectl/usbctl/mdctl/devstat/xpt0/ad0/ad0s1/acd0/ad0s1a/ad0s1b/ufsid/log/pts/zfs"

Fix: 

The problem comes from cddl/contrib/opensolaris/lib/libzfs/common/libzfs_import.c 

The file name is computed using:

  (void) snprintf(path, sizeof (path), "%s/%s", rdsk,
                  dp->d_name);

However, a few lines upper, rpath is assigned to rdev:

  if (strcmp(path, "/dev/dsk/") == 0)
          rdsk = "/dev/rdsk/";
  else
          rdsk = path;

Thes best way to fix that is probably to avoid reusing variables.
How-To-Repeat: Just run zpool import -d /dev