cm_write
cm_write(selstate, conn->fd);
cm_write(selstate, conn->fd);
cm_write(selstate, state->fd);
cuse_write_t *cm_write;
if (cdev->mtod->cm_write != NULL) {
error = (cdev->mtod->cm_write) (cdev, (int)info.fflags,
.cm_write = vclient_write_oss,
.cm_write = vclient_write_wav,