Edirol UM-550 and UM-880
From the ALSA wiki
Edirol UM-550/UM-880 with 2.6 kernel
To get the Edirol UM-550 or UM-880 working with a 2.6 kernel:
- compile your kernel with CONFIG_USB_MIDI
- switch the UM-550 or UM-880 into "ordinary driver mode", following the instructions in the manual.
- note that this will not work with Rosegarden and possibly other fairly recent applications.
- compile your kernel without CONFIG_USB_MIDI (important)
- compile your kernel with CONFIG_SND_USB_AUDIO
- switch the UM-550 or UM-880 into "FPT driver mode", following the instructions in the manual.
- this is the preferred method, as OSS is deprecated.
There is no difference in functionality between the ordinary and FPT drivers in the hardware, this is only related to proper recognition of the device by the OS.
In both cases, you will see obvious signs of success in /var/log/messages or dmesg if you set things up right. Also, for the ALSA driver, you will see the device with 'amidi -l'. If the drivers are compiled as modules, you need to take the normal steps for loading them into your kernel (e.g. modprobe).
Which port is which?
Once the device has been detected by the system, you will get 6 ALSA MIDI ports (for the UM-550, 9 for the UM-880), the last one of which is the device's control port, used to send control information to the device (such as patch change messages, for instance ; this control ports prevents conflicts with other MIDI devices). The other ports correspond to the MIDI inputs and outpus on the device, but numbered from 0 instead of 1, meaning that ALSA port number 0 corresponds to physical port number 1.
To play a MIDI note from the computer to an instrument connected on OUTPUT 2 on you device, send the note to "UM-xx0 Port 1" and check that you have patched INPUT 2 to OUTPUT 2 with the MIDI/USB button lit (which means that the input will come from USB). You can actually send the note to any port n, provided that you patch INPUT (n+1) to OUTPUT 2 (again, with the MIDI/USB button lit).
Also note that you cannot patch USB INPUT 2 to OUTPUT 2 as well as MIDI INPUT 2 to OUTPUT 2 at the same time, but you could patch USB INPUT 3 to OUTPUT 2 and MIDI INPUT 2 to OUTPUT 2 at the same time. This is apparently a limitation of the hardware, and not specific to ALSA or Linux.