pbisla/tinyalsa — comment on commit 26f5f9e9c07006e60f82e8959644b07bdc5c001e
File:  line 0
By tinyalsa:

This is a really useful addition, but the problem is that it creates a PCM which cannot then be used for anything else because most of the pcm_open() setup is not done. This ioctl is fairly lightweight so it makes sense to do this during pcm_open() when the period_size and period_count are obtained.