PyUSB device claimed, detach_kernel_driver return Entity Not Found

Question

I'm attempting to do bulk reads and writes from a USB device on Ubuntu using PyUSB. However, i've been unsuccessful at getting that far.

import usb.core
import usb.util

dev = usb.core.find(idVendor=0xXXXX,idProduct=0xYYYY)
if dev is None:
    raise ValueError('Device not found.')

try:
    dev.detach_kernel_driver(0)
except:
    print "exception dev.detach_kernel_driver(0)"
    pass

dev.set_configuration()
print "all done"

This is the simple script I'm using. I've created /etc/udev/rules.d/40-basic-rules.rules which contains

SUBSYSTEM=="usb", ENV{DEVTYPE}=="usb_device",SYSFS{idVendor}=="XXXX" , SYSFS{idProduct}=="YYYY", MODE="0666"

for my appropriate device.

Running the script as is as root raises a usb.core.USBError: [Errno 16] Resource busy error because the dev.detach_kernel_driver(0) throws the exception usb.core.USBError: [Errno 2] Entity not found

in dmesg I see these messages,

[  638.007886] usb 1-1: usbfs: interface 1 claimed by usb-storage while 'python' sets config #1
[  643.425802] usb 1-1: usbfs: interface 1 claimed by usb-storage while 'python' sets config #1
[  647.957932] usb 1-1: usbfs: interface 1 claimed by usb-storage while 'python' sets config #1

Any thoughts on what I'm missing to get access to this device?

Answer 1

Your problem, like mine, is that you need to detach the kernel from each and every interface before you can set_configuration(). Here's the code I am using right now (including some scaffolding) for connecting to a USB audio device:

import usb.core
import usb.util

scarlet = usb.core.find(idVendor = 0x1235)  # Focusrite
if not scarlet: print"No Scarlet"

c = 1
for config in scarlet:
    print 'config', c
    print 'Interfaces', config.bNumInterfaces
    for i in range(config.bNumInterfaces):
        if scarlet.is_kernel_driver_active(i):
            scarlet.detach_kernel_driver(i)
        print i
    c+=1

scarlet.set_configuration()