[linux-audio-user] Re: [Alsa-devel] Please explain Alsa Interface MIDI numbering PLEASE!

[Clemens Ladisch]

Mark Knecht wrote:
> 1) In the screen shot "without_2x2.png" I see two read ports and two
> write ports. Please explain why they are called
>
> 64:0 External MIDI 0
> 64:32 External MIDI 0
>
> Why is my HDSP given the apparent name '64'?

This isn't the name, it's the sequencer client number. In theory, it
should not be necessary to identify devices by this.

0-63 are reserved for the ALSA core. 64-127 are used by sound cards, with
each card getting 8 (64-71, 72-79, etc.). 128-255 are for use by
applications.

> Why the :0 and :32? I would have thought :0 and :16 would make more
> sense from a channel numbering point of view, or :0 and :1 from an
> interface point of view. What's going on?

These ports are not native sequencer ports implemented directly by the
driver but are emulated on top the rawmidi ports. There can be 256 ports
per sequencer client, and 8 rawmidi devices per card, so each rawmidi
device (which can have an unspecified number of subdevices=ports) is
mapped to a group of 32 (256/8) sequencer ports.

If the two rawmidi ports would have been subdevices of one device, they
would have been mapped to port numbers :0 and :1.

>    How can I change the names that are displayed so that
> "64:0 External MIDI 0" shows the name "HDSP 9652 Port 1"
> "64:32 External MIDI 0" shows the name "HDSP 9652 Port 2"
> "72:0 External MIDI 1" shows the name "MidiSport 2x2 Port A"
> "72:1 External MIDI 1" shows the name "MidiSport 2x2 Port B"

"External MIDI x" is the client name, which is the same for all ports of
the same client. It seems that kaconnect doesn't show the port name, which
would be what you want. Please complain to the author of kaconnect. :-)

To show the port names, run "aconnect -io" or "pmidi -l".


HTH
Clemens