这LPD8是一个音乐物理硬件。插入时，我希望它能够启动Fluidsynth 合成器。在 Debian 上，有一个fluidsynth.service运行--user合成器的实例。
Systemd 在插入设备后即可识别该设备：
$ systemctl --user list-units --type=device
UNIT LOAD ACTIVE DESCRIPTION
...
sys-devices-platform-soc-1c1a000.usb-usb1-1\x2d1-1\x2d1.3-1\x2d1.3:1.0-sound-card1-controlC1.device loaded active plugged LPD8
...
我可以以描述和单位形式查询 LPD8 的状态：
$ systemctl status LPD8.device
○ LPD8.device - /LPD8
Loaded: loaded
Active: inactive (dead)
$ systemctl status sys-devices-platform-soc-1c1a000.usb-usb1-1\x2d1-1\x2d1.3-1\x2d1.3:1.0-sound-card1-controlC1.device
○ sys-devices-platform-soc-1c1a000.usb-usb1-1x2d1-1x2d1.3-1x2d1.3:1.0-sound-card1-controlC1.device - /sys/devices/platform/soc/1c1a000.usb/usb1/1x2d1/1x2d1.3/1x2d1.3:1.0/sound/card1/controlC1
Loaded: loaded
Active: inactive (dead)
但是，我无法add-wants连接fluidsynth.service到 LPD8 设备：systemd 似乎抱怨缺少设备文件。
$ systemctl --user add-wants LPD8.device fluidsynth.service
Failed to add dependency: Unit file LPD8.device does not exist.
$ systemctl --user add-wants sys-devices-platform-soc-1c1a000.usb-usb1-1\x2d1-1\x2d1.3-1\x2d1.3:1.0-sound-card1-controlC1.device fluidsynth.service
Failed to add dependency: Unit file sys-devices-platform-soc-1c1a000.usb-usb1-1x2d1-1x2d1.3-1x2d1.3:1.0-sound-card1-controlC1.device does not exist.
fluidsynth.service当 LPD8 插入时就能够启动，我错过了什么？