CODEWITHSUNDEEP
usblinux-device-driverftdilsusb
Ling Li
Ling Li

Reputation: 21

unbinded USB device get automatically bind on linux

I tried to use echo -n '2-2' > /sys/bus/usb/drivers/usb/unbind to unbind a USB device that connects to FTDI chip, but I found that it get auto binded right after I run the command.

My lsusb -t looks like: 

/:  Bus 02.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/4p, 5000M
    |__ Port 2: Dev 6, If 0, Class=Vendor Specific Class, Driver=usbfs, 5000M
    |__ Port 2: Dev 6, If 1, Class=Vendor Specific Class, Driver=usbfs, 5000M
/:  Bus 01.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/10p, 480M

My lsusb looks like:

Bus 002 Device 006: ID 0403:**** Future Technology Devices International, Ltd 
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

ls /sys/bus/usb/devices has:

1-0:1.0  2-0:1.0  2-2  2-2:1.0  2-2:1.1  usb1  usb2

After I run sudo bash -c 'echo "2-2" > unbind', my dmesg outputs following new messages

[Jan15 11:03] usb 2-2: USB disconnect, device number 3
[  +0.272120] usb 2-2: new SuperSpeed USB device number 4 using xhci_hcd
[  +0.020880] usb 2-2: New USB device found, idVendor=0403, idProduct=***
[  +0.000006] usb 2-2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[  +0.000003] usb 2-2: Product: FTDI **********
[  +0.000003] usb 2-2: Manufacturer: FTDI
[  +0.000002] usb 2-2: SerialNumber: 000000000001

You can see that USB is disconnected, but then new USB is found and get assigned a new device number. It feels like my USB device is rebinded instead of unbind. Does anyone know the reason? Thanks!

More information: I tried run echo -n usb2 > /sys/bus/usb/drivers/usb/unbind to unbind bus 2, it works and dmesg shows:

[Jan15 12:33] usb 2-2: USB disconnect, device number 8

My ls /sys/bus/usb/devices changed to:

1-0:1.0  usb1  usb2

which I feel incorrect. From my understand 2-0:1.0 should alaways be there? Then I tried to add bus2 back by echo -n usb2 > /sys/bus/usb/drivers/usb/bind, I got error in dmesg

[Jan15 12:48] usb usb2: can't set config #1, error -22

Upvotes: 2

Views: 3775

Answers (1)

Blz
Blz

Reputation: 1

While i don't know what is causing the issue You can instead set the authorized parameter to 0 for a USB device as:

echo -n '0' > /sys/bus/usb/devices/X/authorized

This will not only ubind the device but will also stop the USB hub from polling it for changes hence preventing it from being binded again.

You can set authroized to 1 to revert the changes:

echo -n '1' > /sys/bus/usb/devices/X/authorized

Upvotes: 0

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