scsi_get_physical_element_descriptor
allocation_length = dtors * sizeof(struct scsi_get_physical_element_descriptor) +
struct scsi_get_physical_element_descriptor *dtor_ptr;
dtor_ptr = (struct scsi_get_physical_element_descriptor *)(hdr + 1);
_Static_assert(sizeof(struct scsi_get_physical_element_descriptor) == 32,