Через какой девайс обращаться к USB IRDA?

Добавлю, на всякий случай:

#lsmod |grep ir
irtty_sir               8448  2
sir_dev                15748  1 irtty_sir
ircomm_tty             38792  0
ircomm                 22660  1 ircomm_tty
irda                  191036  4 irtty_sir,sir_dev,ircomm_tty,ircomm
crc_ccitt               2176  1 irda

# ls -l /dev/ircomm0
crw-rw-rw- 1 root dialout 161, 0 2007-06-17 12:57 /dev/ircomm0

$ cat /proc/net/irda/discovery
IrLMP: Discovery log:

nickname: SIEMENS M65, hint: 0xb124, saddr: 0x97308257, daddr: 0x00932300

# irdadump
10:02:38.452813 xid:cmd 97308257 > ffffffff S=6 s=0 (14)
10:02:38.540565 xid:cmd 97308257 > ffffffff S=6 s=1 (14)
10:02:38.628596 xid:cmd 97308257 > ffffffff S=6 s=2 (14)
10:02:38.716564 xid:cmd 97308257 > ffffffff S=6 s=3 (14)
10:02:38.804572 xid:cmd 97308257 > ffffffff S=6 s=4 (14)
10:02:38.888585 xid:rsp 97308257 < 00932300 S=6 s=4 SIEMENS M65 hint=b124 [ PnP Modem Fax IrCOMM IrOBEX ] (28)
10:02:38.892553 xid:cmd 97308257 > ffffffff S=6 s=5 (14)
10:02:38.980565 xid:cmd 97308257 > ffffffff S=6 s=* toshiba hint=0400 [ Computer ] (24)

# irdadump -i /dev/ircomm0
Using interface: /dev/ircomm0
ioctl: No such device

попробуй создать файл устройство ircomm0 в ручную. man mknode