[Alsa-user] enumerate MIDI devices

[Brian Sorahan]

Hi all,

I am hoping to get some guidance on how to properly use the information I
get when I list MIDI devices.
I'm tinkering with this code
https://github.com/scgolang/midi/blob/d50a32b1725ae42044c84f02a53c69004926bd93/midi_linux.go#L94-L152
which seems to list MIDI devices ok.
But if I prefer to use the RawMIDI API to actually connect to the device is
this a reasonable way to formulate the device ID?
https://github.com/scgolang/midi/blob/d50a32b1725ae42044c84f02a53c69004926bd93/midi_linux.go#L125
I'm guessing there is a better way to implement this, but I'm pretty new to
the Sequencer API so I'm not sure what that better way might look like.
Does it even make sense to use the Sequencer API to list devices, but then
use the RawMIDI API to open, read, and write?
The code I'm sharing is hopefully readable for C programmers despite the
fact that it is Go.
Thanks in advance for any feedback!

[Clemens Ladisch]

if card := C.snd_seq_client_info_get_card(cinfo); card >= 0 {
device.ID = fmt.Sprintf("hw:%d", card)
}
But if I prefer to use the RawMIDI API to actually connect to the device

That particular device might not be available as a RawMIDI port.

is this a reasonable way to formulate the device ID?

"hw:x" identifies the first RawMIDI port on that card, which is not
necessarily the same as the sequencer port.

To enumerate RawMIDI ports, use snd_ctl_rawmidi_next_device() (see the
source of amidi for an example).

Does it even make sense to use the Sequencer API to list devices, but then
use the RawMIDI API to open, read, and write?

No.


Regards,
Clemens

[Brian Sorahan]

I think that's exactly what I needed! Thanks

Post by Clemens Ladisch

if card := C.snd_seq_client_info_get_card(cinfo); card >= 0 {
device.ID = fmt.Sprintf("hw:%d", card)
}
But if I prefer to use the RawMIDI API to actually connect to the device

That particular device might not be available as a RawMIDI port.

is this a reasonable way to formulate the device ID?

"hw:x" identifies the first RawMIDI port on that card, which is not
necessarily the same as the sequencer port.
To enumerate RawMIDI ports, use snd_ctl_rawmidi_next_device() (see the
source of amidi for an example).

Does it even make sense to use the Sequencer API to list devices, but

then

use the RawMIDI API to open, read, and write?

No.
Regards,
Clemens