PCM_RDCH
ch = PCM_RDCH(dev);
PCM_RDCH(dev) = NULL;
ch = PCM_RDCH(dev);
PCM_RDCH(dev) = NULL;
ch = PCM_RDCH(dev);
PCM_RDCH(dev) = NULL;
} else if (PCM_RDCH(dev) != NULL) {
*rdch = PCM_RDCH(dev);
(ch == PCM_RDCH(i_dev) || /* record ch */
PCM_RDCH(dev) == NULL && PCM_WRCH(dev) == NULL &&
rdch = PCM_RDCH(i_dev);
PCM_RDCH(i_dev) = NULL;
rdch = PCM_RDCH(dev);