[alsa-devel] Question about rawmidi USB Tx buffer size

Simple question: how big is it?

ALSA provides snd_rawmidi_status for reading the status structure from a rawmidi handle, and snd_rawmidi_status_get_avail to extract the number of bytes in the ring buffer from that structure, but what I want to know is how many bytes of space are available in the ring buffer, so that I know how many bytes I can write without blocking. Is the buffer size a fixed number for any particular driver? The only driver I'm concerned with is the USB MIDI driver, so that shouldn't be hardware dependent.