Device::USB::FAQ(3pm)
NAME
Device::USB::FAQ - Frequently Asked Questions for Device::USB
SYNOPSIS
perldoc Device::USB::FAQ
DESCRIPTION
This is an attempt to answer some of the frequently asked questions
about the Device::USB module
QUESTIONS
- Which platforms does Device::USB support?
- "Device:USB" supports any platform that "libusb" supports. This list
currently includes Linux, FreeBSD, NetBSD, OpenBSD, Darwin, and MacOS
X. - There is a port of the "libusb" library to the Windows environment
called "LibUsb-Win32". Because I don't have a development environment
for testing this library, "Device::USB" does not yet support this
library. - 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. This usually causes access to most of
the "libusb" features to fail with a permission error. - Using the "Device::USB" module as root avoids this feature, but is not very satisfying from a security standpoint. (See the next question for more options.)
- 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. 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. - 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. - DEVFS / HOTPLUG
- 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. - 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"USBFSThe 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 0The value 118 in the above should be replaced with the group id of your usb group (created above). 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. 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.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 0to
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 0Once again, this needs to be all on one line with the "\" characters
removed.
SEE ALSO
Device::USB and the "libusb" library site at
<http://libusb.sourceforge.net/>.
AUTHOR
G. Wade Johnson (wade at anomaly 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.
COPYRIGHT & LICENSE
Copyright 2006 Houston Perl Mongers
- This document is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.