Hi all,

This patch adds a USB MIDI Gadget driver. This driver is glue between
the USB gadget interface and the ALSA MIDI interface. It allows an
embedded Linux system to appear as a class-compliant USB-MIDI device
to a host system on the other end of a USB cable.

Much of the code is borrowed from zero.c, usbmidi.c and usbaudio.c;
my thanks to David, Clemens and Takashi for their work.

Included are usb_audio.h and usb_midi.h containing definitions from
the relevant USB specifications for USB audio and USB MIDI devices.
The definitions of struct usb_ms_header_descriptor and struct
usb_ms_endpoint_descriptor are the same as those that appear in
sound/usb/usbmidi.c, with the intention of that file including
<linux/usb_midi.h> instead. I have not included that change here.

This patch is against v2.6.17. I have tested using dummy_hcd inside
user-mode linux, and using s3c2410_udc. Testing with user-mode linux
requires minor changes to a few Kconfig files in order to enable the
USB and sound subsystems with ARCH=um.

I have tested playing a midi file with aplaymidi at one end and dumping
the events with amidi at the other (in both directions) as well as
connecting to a Mac running a synth with Garage Band.

All comments are welcome. If the response is favourable then I'll submit
this driver to the USB folks for inclusion.

Cheers,

- Ben.


P.S. My apologies if it's inappropriate to cross-post to linux-usb-devel
and alsa-devel, I'm hoping you're both interested. :)

P.P.S. My first attempt at emailing a patch with Thunderbird. Whitespace
was munged when inline, so I hope a text/plain attachment is ok.