[alsa-devel] Difference between boundary and buffer_size

The code in the kernel, in /pcm_lib.c/ and /pcm_native.c/, uses fields buffer_size and boundary in struct snd_pcm_runtime. As far as I can see, there are always initialized to the same value. In what circumstance might they be different? There is clearly some relationship to hw_ptr_base, as illustrated by this repeated snipped from snd_pcm_update_hw_ptr0()

hw_base += runtime->buffer_size; if (hw_base >= runtime->boundary) { hw_base = 0; crossed_boundary++; } new_hw_ptr = hw_base + pos;

Alan.