int snd_dma_set_reserved (const struct snd_dma_device * dev, struct snd_dma_buffer * dmab);
Reserves the given buffer as a reserved buffer. When an old reserved buffer already exists, the old one is released and replaced with the new one.
When NULL buffer pointer or zero buffer size is given, the existing buffer is released and the entry is removed.
Returns zero if successful, or a negative code at error.