Provided by: libdevice-usb-perl_0.37-2build1_amd64 bug


       Device::USB::FAQ - Frequently Asked Questions for Device::USB


       perldoc Device::USB::FAQ


       This is an attempt to answer some of the frequently asked questions about the Device::USB


   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


         groupadd --system usb

       You can then add users to that group to allow access to your usb devices.




       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"


       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,\
             0 0

       The 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 0


         usbfs   /proc/bus/usb   usbfs  noauto,\
             0 0

       Once again, this needs to be all on one line with the "\" characters removed.


       Device::USB and the "libusb" library site at <>.


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

       Houston Perl Mongers Group


       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 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.