USB / udev only work for root

USB / udev only work for root

[Sarah Messer]

Hello,

I can only communicate with a USB device using libusb when I'm logged in as root.  I reported this previously for libusb-0.1.12, and have since tried upgrading to libusb-1.0 with the libusb-compat patch.

My system:
OpenSUSE 10.3, i386
communication is with a Tektronix TDS2014B oscilloscope using pyusb (a Python wrapper for libusb-0.1)
udev version 114-19

The problem is not present on an OpenSUSE 10.0 machine running identical code with straight libusb-0.1/pyusb

/etc/udev/rules.d/55-libsane.rules contains the following lines (among many others):

# ENV{DEVTYPE}="usb_device", NAME="bus/usb/$env{BUSNUM}/$env{DEVNUM}", MODE="0664", OWNER="root", GROUP="root"

SUBSYSTEM="usb", ACTION="add|change", SYSFS{idVendor}="0699", SYSFS{idProduct}="0368", GROUP="usb", MODE="0664"

The 'scope's /dev/bus/usb/ entry looks like:
crw-rw-r-- 1 root usb  189, 132 2009-01-02 17:09 005

The non-root user who tried to use this scope is a member of these groups:
users dialout uucp video usb

Further notes:
1)  Other USB devices which aren't being accessed via libusb are accessible to non-root users (e.g. printer, thumbdrive)
2)  System seems to require an external hub between the scope and PC for reliable communication, but I _think_ that's a separate hardware issue since it's present on both machines.
3)  The exact error message is "error sending control message: Operation not permitted"
4)  I can get an (apparently valid) DeviceHandle, but both reset() and getString() calls fail - with permissions as the cited reason.

Any guidance you can provide on the likely source of the problem (or troubleshooting tricks) would be welcome.

Thanks

-Sarah


      

Re: USB / udev only work for root

[Piter PUNK]

Sarah Messer wrote:
> The problem is not present on an OpenSUSE 10.0 machine running identical code with straight libusb-0.1/pyusb
> 
> /etc/udev/rules.d/55-libsane.rules contains the following lines (among many others):
> 
> # ENV{DEVTYPE}="usb_device", NAME="bus/usb/$env{BUSNUM}/$env{DEVNUM}", MODE="0664", OWNER="root", GROUP="root"
> 
> SUBSYSTEM="usb", ACTION="add|change", SYSFS{idVendor}="0699", SYSFS{idProduct}="0368", GROUP="usb", MODE="0664"

Change SYSFS to ATTRS.

Piter Punk

Re: USB / udev only work for root

[Sarah Messer]

Changing SYSFS -> ATTRS in 55-libsane.rules worked.  Thanks

For the record, the command sequence I use (in pyusb) is:

import usb        #sets up libusb
...
allBus=usb.busses()   #read in a list of available USB busses
...
bus=allBus[bIndex]       #focus on bus number bIndex
dev=bus.devices[dIndex]   #focus on device number dIndex on that bus
handfiv.open()            #open that device and return the DeviceHandle
                #read the device serial number as a string
                #prepend 'USB' to distinguish this from RS-232 equipment
                #on the same system
thisSerNum='USB'+hand.getString(dev.iSerialNumber, USB_SHORT_BUFF)   
...

Ellipsis marks omitted code which sets up variables and is not directly related to the usb managment.  

The code fails at the hand.getString() call (with SYSFS in the .rules file).

This code is part of a device-identification loop, and so there is no claimInterface() command.  Device-descriptor queries like the above are necessary to determine which interfaces are available for claiming.

Thanks for your help.

-Sarah


--- On Sat, 1/3/09, Piter PUNK <piterpunk@unitednerds.org> wrote:

> From: Piter PUNK <piterpunk@unitednerds.org>
> Subject: Re: USB / udev only work for root
> To: "Sarah Messer" <ikustosu@yahoo.com>
> Cc: "libusb-devel" <libusb-devel@lists.sourceforge.net>, linux-hotplug@vger.kernel.org
> Date: Saturday, January 3, 2009, 12:24 PM
> Sarah Messer wrote:
> > The problem is not present on an OpenSUSE 10.0 machine
> running identical code with straight libusb-0.1/pyusb
> > 
> > /etc/udev/rules.d/55-libsane.rules contains the
> following lines (among many others):
> > 
> > # ENV{DEVTYPE}="usb_device",
> NAME="bus/usb/$env{BUSNUM}/$env{DEVNUM}",
> MODE="0664", OWNER="root",
> GROUP="root"
> > 
> > SUBSYSTEM="usb",
> ACTION="add|change",
> SYSFS{idVendor}="0699",
> SYSFS{idProduct}="0368", GROUP="usb",
> MODE="0664"
> 
> Change SYSFS to ATTRS.
> 
> Piter Punk


      
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