Device::USB::FAQ(3pm)

💖 Device::USB::FAQ — the FAQ bestie 💖

okay so this is Device::USB::FAQ(3pm) from the User Contributed Perl Documentation, and it's literally just a big ol' pile of questions people kept asking about Device::USB. So I gathered them all up, put them in one place, and now you don't have to dig through the group chat to find the answers. 🫶

---

✨ NAME ✨

Device::USB::FAQ — Frequently Asked Questions for Device::USB. That's it, that's the name, iconic.

🌸 SYNOPSIS 🌸

perldoc Device::USB::FAQ

periodt. that's the whole vibe. 💅

🦋 DESCRIPTION 🦋

okay so this is an attempt to answer some of the frequently asked questions about the Device::USB module. genuinely an attempt. we're doing our best and our best is actually pretty good ngl. ✨

---

🎀 QUESTIONS 🎀

💜 Which platforms does Device::USB support?

Device:USB supports any platform that libusb supports. and the list right now is: Linux, FreeBSD, NetBSD, OpenBSD, Darwin, and MacOS X. so like, the whole cool-kid Unix crew showed up. 👑

there's also a port of the libusb library to the Windows environment called LibUsb-Win32. but there's a whole thing: because I don't have a development environment for testing this library, Device::USB does not yet support this library. not me having no Windows machine 😭 it's giving "we'll get to it."

😭 Do I have to use Device::USB as root?

by default, access to the USB devices on a Unix-based system appear to be limited to the root account. which means access to most of the libusb features usually just fails with a permission error. rude. 💀

using the Device::USB module as root avoids this feature, but it is not very satisfying from a security standpoint. like bestie, running everything as root is not the slay you think it is. (see the next question for more options — we got you. 🫶)

🧚 How do I enable use of Device::USB as a non-root user?

some of the attributes of USB devices are available to non-root users, but accessing many of the more interesting features require special privileges. lowkey the good stuff is locked behind a door. 🔒

according to the libusb source, the open() function requires either device nodes to be present or the usbfs file system to be mounted in specific locations. those places, in order, are:

1. /dev/bus/usb — pre-2.6.11: via devfs / post-2.6.11: via udev
2. /proc/bus/usb — usbfs

look in both locations on your system for which of these two methods your libusb will use. vibe check your filesystem, bestie. 🌈

no matter which method your system uses, you will probably want to create a separate group to control access. run this command to add a system group:

addgroup --system usb

or

groupadd --system usb

you can then add users to that group to allow access to your usb devices. so everyone in the group gets in the club. 🎀

🍓 DEVFS / HOTPLUG

TODO

(not me leaving this one blank 🙈 it's literally what the page says, bestie. TODO means TODO.)

✨ UDEV

if you use Debian/Ubuntu, look in the /etc/udev/permissions.rules file. if you want to allow global access to all usb devices, make this change:

change this:

SUBSYSTEM=="usb_device", MODE="0664"

to this:

SUBSYSTEM=="usb_device", MODE="0664", GROUP="usb"

after you reboot, all usb devices will inherit the mode and group specified. one line, one reboot, whole new world. 🔥

if you want to only change permissions for certain devices, you can add this on one line and adjust the product and vendor IDs:

SUBSYSTEM=="usb_device", GROUP="usb", \
  SYSFS{idVendor}=="1234", SYSFS{idProduct}=="1234"

adjust the product and vendor IDs — that part is on you, i can't read your hardware's mind. 💅

💫 USBFS

the usbfs defaults to root as the user and group. this can be changed in the /etc/fstab by adding the following on one line:

none /proc/bus/usb usbfs noauto,\
    listuid=0,listgid=118,listmode=0664,\
    busuid=0,busgid=118,busmode=0775,\
    devuid=0,devgid=118,devmode=0664\
    0 0

the value 118 in the above should be replaced with the group id of your usb group (created above). so swap the 118, bestie, don't just copy it. 🫠

the list* values are to allow listing devices, the bus* is to control access to the bus directories and the dev* values control access to the device files.

okay important note: this approach does not allow the kind of granular permission that the udev approach gives, so it is all or nothing unless permissions are changed programmatically. so like, no pick-and-choose. it's giving all-access pass or nothing. 🎟️

if your /etc/fstab file already has a line for /proc/bus/usb, add the options above to the line that is already there rather than adding the new line. for example, you would change

usbfs   /proc/bus/usb   usbfs   noauto  0 0

to

usbfs   /proc/bus/usb   usbfs  noauto,\
    listuid=0,listgid=118,listmode=0664,\
    busuid=0,busgid=118,busmode=0775,\
    devuid=0,devgid=118,devmode=0664\
    0 0

once again, this needs to be all on one line with the \ characters removed. i know the backslashes look cute but they gotta GO. 😭

---

👀 SEE ALSO 👀

Device::USB and the libusb library site at <http://libusb.sourceforge.net/>. go read, bestie. 📚

🌟 AUTHOR 🌟

G. Wade Johnson (gwadej at cpan dot org) Paul Archer (paul at paularcher dot org)

Houston Perl Mongers Group

🫶 ACKNOWLEDGEMENTS 🫶

thanks go to various users who submitted questions and answers for the list. in particular, Anthony L. Awtrey who contributed the first FAQ answer. the founding member of the FAQ, the OG, the main character. 👑

📜 COPYRIGHT & LICENSE 📜

Copyright 2006-2013 Houston Perl Mongers

this document is free software; you can redistribute it and/or modify it under the same terms as Perl itself. free as in freedom, as in go wild. ✨

---

okay and that's the whole page! 💖 this was Device::USB::FAQ(3pm), part of perl v5.42.3, dated 2026-08-19. love that for us. no cap. slay. 🎀🦋🌸💅