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after restart my system , E1750 work ok!
but when I Re-plug the usb device,E1750 can't work (no /dev/ttyUSB0)

info：

cent os 5.4 x64 Huawei E1750
“uname -a” ： Linux 2.6.18-164.el5 #1 SMP Thu Sep 3 03:28:30 EDT 2009 x86_64 x86_64 x86_64 GNU/Linux

"less usb_modeswitch.setup"
DefaultVendor= 0x12d1
DefaultProduct= 0x1446
TargetVendor= 0x12d1
TargetProduct= 0x1001
MessageContent="55534243123456780000000000000011060000000000000000000000000000":
MessageEndpoint=0x01
CheckSuccess=5
HuaweiMode=0



--------------restart my system ,then run "usb_modeswitch -W -c usb_modeswitch.setup"
dmesg.log:
usb 1-8: usbfs: process 3549 (usb_modeswitch) did not claim interface 0 before use
usb 1-8: USB disconnect, address 3
usb 1-8: new high speed USB device using ehci_hcd and address 4
usb 1-8: configuration #1 chosen from 1 choice
usb-storage: probe of 1-8:1.0 failed with error -5
usb-storage: probe of 1-8:1.1 failed with error -5
usb-storage: probe of 1-8:1.2 failed with error -5
scsi7 : SCSI emulation for USB Mass Storage devices
usb-storage: device found at 4
usb-storage: waiting for device to settle before scanning
scsi8 : SCSI emulation for USB Mass Storage devices
usb-storage: device found at 4
usb-storage: waiting for device to settle before scanning
usbcore: registered new driver usbserial
drivers/usb/serial/usb-serial.c: USB Serial support registered for generic
usbcore: registered new driver usbserial_generic
drivers/usb/serial/usb-serial.c: USB Serial Driver core
drivers/usb/serial/usb-serial.c: USB Serial support registered for GSM modem (1-port)
option 1-8:1.0: GSM modem (1-port) converter detected
usb 1-8: GSM modem (1-port) converter now attached to ttyUSB0
option 1-8:1.1: GSM modem (1-port) converter detected
usb 1-8: GSM modem (1-port) converter now attached to ttyUSB1
option 1-8:1.2: GSM modem (1-port) converter detected
usb 1-8: GSM modem (1-port) converter now attached to ttyUSB2
usbcore: registered new driver option
drivers/usb/serial/option.c: USB Driver for GSM modems: v0.7.1
Vendor: HUAWEI Model: Mass Storage Rev: 2.31
Type: CD-ROM ANSI SCSI revision: 02
sr1: scsi-1 drive
sr 7:0:0:0: Attached scsi CD-ROM sr1
sr 7:0:0:0: Attached scsi generic sg2 type 5
usb-storage: device scan complete
Vendor: HUAWEI Model: SD Storage Rev: 2.31
Type: Direct-Access ANSI SCSI revision: 02
sd 8:0:0:0: Attached scsi removable disk sdb
sd 8:0:0:0: Attached scsi generic sg3 type 0
usb-storage: device scan complete

"lsusb" : Bus 005 Device 005: ID 12d1:1001 Huawei Technologies Co., Ltd. E620 USB Modem


------Re-plug the usb device ,then run "usb_modeswitch -W -c usb_modeswitch.setup"
dmesg.log:
usb 5-2: usbfs: process 6184 (usb_modeswitch) did not claim interface 0 before use
usb 5-2: USB disconnect, address 4
usb 5-2: new full speed USB device using uhci_hcd and address 5
usb 5-2: configuration #1 chosen from 1 choice
usb-storage: probe of 5-2:1.0 failed with error -5
usb-storage: probe of 5-2:1.1 failed with error -5
usb-storage: probe of 5-2:1.2 failed with error -5
scsi44 : SCSI emulation for USB Mass Storage devices
usb-storage: device found at 5
usb-storage: waiting for device to settle before scanning
scsi45 : SCSI emulation for USB Mass Storage devices
usb-storage: device found at 5
usb-storage: waiting for device to settle before scanning
Vendor: HUAWEI Model: Mass Storage Rev: 2.31
Type: CD-ROM ANSI SCSI revision: 02
sr1: scsi-1 drive
sr 44:0:0:0: Attached scsi CD-ROM sr1
sr 44:0:0:0: Attached scsi generic sg2 type 5
usb-storage: device scan complete
Vendor: HUAWEI Model: SD Storage Rev: 2.31
Type: Direct-Access ANSI SCSI revision: 02
sd 45:0:0:0: Attached scsi removable disk sdb
sd 45:0:0:0: Attached scsi generic sg3 type 0
usb-storage: device scan complete


"lsusb" : Bus 005 Device 005: ID 12d1:1001 Huawei Technologies Co., Ltd. E620 USB Modem

[covered]

I have solved this problem:
rmmod option
rmmod usbserial

When I unplug the usb device,

lsmod |grep usb
usbserial 67377 1 option

"usbserial" still occupied