1

Sometimes I need to unplug and connect a USB flash memory device to fix a problem.

Is there a way to do it in software?

2 Answers 2

1

Save the following as usbreset.c :

/* usbreset -- send a USB port reset to a USB device */

#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/ioctl.h>

#include <linux/usbdevice_fs.h>


int main(int argc, char **argv)
{
    const char *filename;
    int fd;
    int rc;

    if (argc != 2) {
        fprintf(stderr, "Usage: usbreset device-filename\n");
        return 1;
    }
    filename = argv[1];

    fd = open(filename, O_WRONLY);
    if (fd < 0) {
        perror("Error opening output file");
        return 1;
    }

    printf("Resetting USB device %s\n", filename);
    rc = ioctl(fd, USBDEVFS_RESET, 0);
    if (rc < 0) {
        perror("Error in ioctl");
        return 1;
    }
    printf("Reset successful\n");

    close(fd);
    return 0;
}

The run the following commands in terminal:

Compile the program:

$ cc usbreset.c -o usbreset

Get the Bus and Device ID of the USB device you want to reset:

$ lsusb  
Bus 002 Device 003: ID 0fe9:9010 DVICO 

Make our compiled program executable:

$ chmod +x usbreset

Execute the program with sudo privilege; make necessary substitution for <Bus> and <Device> ids as found by running the lsusb command:

$ sudo ./usbreset /dev/bus/usb/002/003  

Source: https://askubuntu.com/questions/645/how-do-you-reset-a-usb-device-from-the-command-line

2
  • Thank you for making it non-programmer friendly! How does it differ from a/sys/bus/ based solution? Is it better?
    – unfa
    Sep 20, 2018 at 11:16
  • Also: I have trouble finding what bus/port I need to feed to it based on a /dev/sdX device node name.
    – unfa
    Sep 20, 2018 at 13:06
0

I've made a script for that. Just feed it the name of the device node in /dev/ and it'll do what you want. Save the below code to a script and use it like sudo ./reset-drive.sh sdb. It's made to only work for USB mass storage class devices, so it'll not affect anything else (hard drives, USB mice, keyboards) - that makes it safer. You can tell it to reset your hard drive - it won't work.

#!/bin/bash
drive="$1" # expects input like "sda" "sdc" etc.

cd /sys/bus/usb/drivers/usb-storage

for i in *; do
  if [[ $(udevadm info -q path -n "/dev/$drive" | grep -c "$i") == "1" ]]; then
    echo $i > unbind
    echo $i > bind
  fi
done

How does this work?

Go to the directory containing port information aboout devices in USB Mass Storage class:

cd /sys/bus/usb/drivers/usb-storage

Now evaluate all devices listed there to find one that matches the given device node.

for i in *; do
  if [[ $(udevadm info -q path -n "/dev/$drive" | grep -c "$i") == "1" ]]; 
then

Once it's found, feed the corresponding USB port path name to the unbind and bind files that are used to issue port commands:

echo $i > unbind
echo $i > bind

PS: This solution was based on the following article: http://billauer.co.il/blog/2013/02/usb-reset-ehci-uhci-linux/

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