[yocto] Why isn't USB MIDI working?

[Paul D. DeRocco]

> From: Paul Eggleton
> 
> On Sunday 14 April 2013 15:49:12 Paul D. DeRocco wrote:
> > I've built core-image-base-cedartrail-nopvr, which includes 
> > ALSA. /dev/snd
> > properly contains the devices for my mobo, and 
> > /proc/asound/devices lists
> > them as well. If I plug in a USB MIDI device (a USB to MIDI 
> > converter), I
> > see the USB connect message on the console, but no device 
> > is added to
> > /dev/snd or /proc/asound/devices. Anyone have any idea why? 
> > I've tried an
> > eMu XMidi1x1, and a cheap generic converter. Both work fine 
> > under Ubuntu, on
> > the same mobo.
> 
> Typically two things are required for a USB device to work - 
> a driver, and an 
> appropriate udev rule to associate the driver with the 
> device. Do you have USB 
> midi support enabled in the kernel? If so, is there a udev 
> rule for USB midi 
> devices? If there isn't, presumably you could just use Ubuntu 
> as a reference 
> for that.

I apologize for my ignorance, but I really don't know how to go about
figuring this out.

There is a file called /lib/udev/rules.d/60-persistent-alsa.rules, which is
full of cryptic stuff that I don't understand, including two lines referring
to usb, but nothing specifically about MIDI. I compared it to the file on
Ubuntu, and it's similar but not the same, but I have no idea whether any of
the differences are meaningful. They're both small, so I've attached them.

Also, I see that while the alsa-utils recipe is being built, the resulting
image only seems to have a couple of alsa utilities: alsamixer and alsactl,
even though there are a whole lot more listed in
meta/recipes-multimedia/alsa/alsa-utils_1.0.25.bb.

And when I run the system, there is no /dev/snd/seq device, which is the
main interface to all MIDI devices. I don't plan on using that, preferring
to use the /dev/snd/midi* OSS emulation device which is supposed to appear
when an individual device is connected, but that's not happening, either.

How do I find out if USB MIDI support is enabled in the kernel?

This is plain vanilla core-image-base-cedartrail-nopvr, without any
modifications. ALSA is part of it. Isn't it supposed to just work?

-- 

Ciao,               Paul D. DeRocco
Paul                mailto:pderocco at ix.netcom.com 
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