Sound drivers - meaning of "status" string, passed to pcm_setstatus()

[fesse]

Hi,

Sound subsystem has pcm_setstatus(device_t, char *) function, and its second param is string with size, limited to SND_STATUSLEN. Existing drivers puts something like "at io " followed by base address and size of device i/o and irq number.

What exactly this status string should contain? Where it is used? Why have it?
Since /dev/sndstat doesn't display this info, and mixer too.