idea: "shim" driver for Roland / Edirol SD-20 MIDI sound module?

Torfinn Ingolfsen torfinn.ingolfsen at
Mon Feb 21 22:49:15 UTC 2011


I have a Roland / Edirol SD-20[1] MIDI sound module, from the Studio Canvas[2] line.
It connects via usb to a computer (it can connect vis serial too, but why use that when usb is everywhere?).

Anyway, this module isn't getting picked up by the usb midi drivers of FreeBSD because it doesn't
advertise iutself as "usb midi class", but instead uses "usb vendor class", if I have understood this correctly.
In all other ways, the SD-20 is a general MIDI (GM2) device, if I understand correctly.
usb device descriptor, current config etc. on my page for the SD-20[3].

Now, here is my idea: if there was a "shim" (usb) device driver under FreeBSD, which would attach to this device,
and do just two things:
a) modify the "usb class " of the device to be "usb midi" instead of "usb vendor"
b) transparently forward all other requests (and responses) to and from the device

the effect would be (I hope) that FreeBSD would see a new usb midi device, and the "normal" usb midi drivers would attach to this device.
Voila! A driver for this almost-standard usb midi device (Roland SD-20), which would re-use the existing MIDI drivers.

So, would this work, or not?

Torfinn Ingolfsen

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