华为ET127 td网卡，使用3g-modem程序成功将设备转换为modem模式，但使用pppd拨号时出现了failed to open /dev/ttyUSB0的错误，不知道是什么原因。
(ZTE AC2710用这种方法是成功的，支持列表有这个型号）
[root@FriendlyARM /]# lsusb Bus 001 Device 002: ID 12d1:1da1 Huawei Technologies Co., Ltd. Bus 001 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
[root@FriendlyARM /]# 3g-modem -v 12d1 -p 1da1 -V 12d1 -P 1d09 -H -I -W -s 20 Taking all parameters from the command line
DefaultVendor= 0x12d1
DefaultProduct= 0x1da1
TargetVendor= 0x12d1
TargetProduct= 0x1d09
TargetClass= not set
TargetProductList=""
DetachStorageOnly=0
HuaweiMode=1
SierraMode=0
SonyMode=0
GCTMode=0
MessageEndpoint= not set
MessageContent=""
NeedResponse=0
ResponseEndpoint= not set
Interface=0x00
InquireDevice disabled
Success check enabled, max. wait time 20 seconds
System integration mode disabled
usb_set_debug: Setting debugging level to 15 (on)
usb_os_find_busses: Found 001
usb_os_find_busses: Skipping non bus directory devices
usb_os_find_devices: Found 002 on 001
usb_os_find_devices: Found 001 on 001
error obtaining child information: Inappropriate ioctl for device
Looking for target devices ...
searching devices, found USB ID 12d1:1da1
found matching vendor ID
searching devices, found USB ID 1d6b:0001
No devices in target mode or class found
Looking for default devices ...
searching devices, found USB ID 12d1:1da1
found matching vendor ID
found matching product ID
adding device
searching devices, found USB ID 1d6b:0001
Found devices in default mode or class (1)
Accessing device 002 on bus 001 ...
USB description data (for identification)
-------------------------
Manufacturer: HUAWEI Mobile
Product: HUAWEI Mobile System Solution
Serial No.: 666666-66-666666
-------------------------
Sending Huawei control message ...
OK, Huawei control message sent
Checking for mode switch (max. 20 times, once per second) ...
Waiting for original device to vanish ...
Check that you have permissions to write to 001/002 and, if yousb 1-1: USB disc2
u don't, that you set up hotplug (
http://linux-hotplug.sourceforge.net/) correc.
USB error: could not claim interface 0: Device or resource busy
Original device can't be accessed anymore. Good.
Searching for target devices ...
usb_os_find_devices: Found 002 on 001
usb_os_find_devices: Found 001 on 001
error obtaining child information: Inappropriate ioctl for device
searching devices, found USB ID 12d1:1da1
found matching vendor ID
searching devices, found USB ID 1d6b:0001
Searching for target devices ...
usb 1-1: new full speed USB device using s3c2410-ohci and address 3
usb 1-1: New USB device found, idVendor=12d1, idProduct=1d09
usb 1-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
usb 1-1: Product: HUAWEI Mobile System Solution
usb 1-1: Manufacturer: HUAWEI Mobile
usb 1-1: SerialNumber: 666666-66-666666
one_wire_status: 4
scsi1 : usb-storage 1-1:3.7
usb_os_find_devices: Found 001 on 001
searching devices, found USB ID 1d6b:0001
scsi 1:0:0:0: CD-ROM HUAWEI Mobile CMCC CD 1.25 PQ: 0 ANSI: 0
Searching for target devices ...
usb_os_find_devices: Found 003 on 001
skipped 3 class/vendor specific interface descriptors
skipped 4 class/vendor specific interface descriptors
skipped 4 class/vendor specific interface descriptors
skipped 4 class/vendor specific interface descriptors
usb_os_find_devices: Found 001 on 001
error obtaining child information: Inappropriate ioctl for device
searching devices, found USB ID 12d1:1d09
fscsi 1:0:0:0: Attached scsi generic sg0 type 5
ound matching vendor ID
found matching product ID
adding device
searching devices, found USB ID 1d6b:0001
Found target device 003 on bus 001
Target device description data
-------------------------
Manufacturer: HUAWEI Mobile
Product: HUAWEI Mobile System Solution
Serial No.: 666666-66-666666
-------------------------
Found correct target device
Mode switch succeeded. Bye.
[root@FriendlyARM /]# lsusb Bus 001 Device 003: ID 12d1:1d09 Huawei Technologies Co., Ltd.[root@FriendlyARM /]# mknod /dev/ttyUSB0 c 188 0
[root@FriendlyARM /]# mknod /dev/ttyUSB1 c 188 1
[root@FriendlyARM /]# mknod /dev/ttyUSB2 c 188 2
[root@FriendlyARM /]# mknod /dev/ttyUSB3 c 188 3[root@FriendlyARM /]# pppd call tdscdma Failed to open /dev/ttyUSB0: No such device
