PCM_WRCH
ch = PCM_WRCH(dev);
PCM_WRCH(dev) = NULL;
ch = PCM_WRCH(dev);
PCM_WRCH(dev) = NULL;
} else if (PCM_WRCH(dev) != NULL) {
ch = PCM_WRCH(dev);
PCM_WRCH(dev) = NULL;
*wrch = PCM_WRCH(dev);
ch == PCM_WRCH(i_dev))) { /* playback ch */
PCM_RDCH(dev) == NULL && PCM_WRCH(dev) == NULL &&
wrch = PCM_WRCH(i_dev);
PCM_WRCH(i_dev) = NULL;
wrch = PCM_WRCH(dev);