I habe a driver for my ELM 327 an it uses the pl2303 module which depends on the usbserial and this again depends on the pl2303 module.

What I tried:

sudo modprobe -r usbserial pl2303
sudo modprobe -r pl2303 usbserial
sudo modprobe -rf usbserial
sudo modprobe -rf pl2303
sudo rmmod --force pl2303
sudo rmmod --force usbserial

result of rmmod:

rmmod: ERROR: ../libkmod/libkmod-module.c:799 kmod_module_remove_module() could not remove 'usbserial': Resource temporarily unavailable
rmmod: ERROR: could not remove module usbserial: Resource temporarily unavailable

result of modprobe:

modprobe: FATAL: Module usbserial is in use.

Also I tried it with the drivers loaded and unloaded.

kernel modules reference each other[1]

OS: Ubuntu 20.04

  • 1
    To start with, which Linux distro have you installed (Ubuntu server, Ubuntu desktop, Kubuntu, Lubuntu, Xubuntu, Ubuntu MATE, Mint, et al.), & which release number? Different releases have different tools for us to recommend. Please click edit & add that to your question, so all facts we need are in the question. Please don't use Add Comment, since that's our one-way channel to you. All facts about your PC should go in the Question with edit as this is a Q&A site, not a general forum, so things work differently here. – K7AAY May 26 at 17:11
  • Some additional reading on pl2303: EP-44 serial printer via USB adapter: Linux – WinEunuuchs2Unix May 31 at 20:03

It's possible to blacklist kernel modules.

Checkout this post about How to blacklist kernel modules?

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  • Although you answered your own question, I'm upvoting to help you recover lost bounty points. – WinEunuuchs2Unix May 31 at 20:17

When you look into dmesg do you see a line where the device was detected when it was plugged in? Ubuntu should have FTDI support out of the box. Normally you would just access it by typing screen /dev/ttyUSB# 38400.

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  • Thank you for the response. But I don't want to connect to like that. I just need to unload it from the kernel. – Noel Schenk May 29 at 12:51
  • You could try blacklisting it by editing /etc/modprobe.d/blacklist and adding blacklist driver-name. Maybe that will work for you. – ognjen May 29 at 15:10

As OP mentioned rather than unloading module it is easier to not load it in the first place. This is accomplished by blacklisting the module:

To summarize answers in link:

Just open your /etc/modprobe.d/blacklist.conf file and add drivername using following syntax:

blacklist pl2303

Save the file and Reboot. The offending module will no longer be loaded at startup.

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