[LAU] midi sub-devices in OSS emulation

Brent Busby brent at keycorner.org
Mon Apr 9 19:25:46 CEST 2018


Clemens Ladisch <clemens at ladisch.de> writes:

> Brent Busby wrote:
>> Is there a way to access individual subdevices through the OSS emulation?
>
> Short answer: no.
> Long answer: opening a device will open the first available subdevice.
>
>> What is the difference between midi, dmmidi, amidi, and admmidi?
>
> /dev/midiX and /dev/dmmidiX are the same.
> /dev/amidiX and /dev/admmidiX are the same.
>
> /dev/midiX is MIDI device 0 of card X.
> /dev/amidiX is MIDI device 1 of card X.

So by virtue of the 'a' prefix device nodes, I actually get the second
subdevice after the one that's mapped (described in your amidi_map
description below) for free?  (Or am I interpreting that wrong?)

It looks like I can control the first subdevice that gets exported as a
device node with the amidi_map= option you describe below, plus I also
get the subdevice after that (n+1) on the same device node with the 'a'
prefix added...so I can have two.  I may have that wrong.

Just wondering though, what is the purpose of the 'dm' prefix nodes if
they do the same thing?

> You can change the OSS device numbers with the midi_map and amidi_map options
> of the snd-rawmidi module, with one number per card.  E.g., to let /dev/amidi4
> point to device 2, use "options snd-rawmidi amidi_map=1,1,1,1,2".

That's very useful to at least be able to choose which subdevice gets
the OSS exposure.

-- 
- Brent Busby	+ ===============================================
		+ "The introduction of a new kind of music must
-- Studio    --	+  be shunned as imperiling the whole state, for
-- Amadeus/  --	+  styles of music are never disturbed without
-- Keycorner --	+  without affecting the most important political
-- Recording --	+  institutions."    --Plato, "Republic"
----------------+ ===============================================


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