Re: [Libusb-devel] Still can't claim interface, "No such file or directory" (Part 1)

[Alan S. <st...@ro...>]

On Sat, 17 Oct 2009, Kustaa Nyholm wrote:

> " Mount debugfs (it has to be enabled in your kernel configuration), and
> " load the usbmon module (if built as module). The second step is skipped
> " if usbmon is built into the kernel.   
> "       mount -t debugfs none_debugs /sys/kernel/debug
> "       modprobe usbmon
> 
> Note the 'none_debugs' is slightly different from what Alan wrote and
> that the second step may not be necessary.

That particular word in this mount command is ignored.  You can put
almost anything you want in that spot.  "none" is traditional.

>  (I'm not complaining
> just detailing what I did posterity) From some other 
> web page I noted that Ubuntu 9.04 has some usbmon related
> stuff 'enabled' and there is no need to recompile the kernel,
> so I infered that maybe I do not need that second step.
> 
> Is this correct?

Yes.

> Ok, moving on. I verified, as explained in the usbmon.txt, that
> I can do:
>  
> ls /sys/kernel/debug/usbmon
> 0s  0u  1s  1t  1u  2s  2t  2u  3s  3t  3u  4s  4t  4u
> 
> But trying to find out about my device using:
> 
> cat /proc/bus/usb/devices
> 
> fails, because there is nothing under  /proc/bus/usb/
> however all the devices in my system can be found
> under /dev/bus/usb 
> 
> Is this ok / significant?

It is okay.  You can get the information about your device from the
dmesg log; it shows that your device was on bus 2.  So you could have
used the 2u file, but 0u is okay.

> Anyway, I did:
> 
> sudo cat /sys/kernel/debug/usbmon/0u >/home/nyholku/Desktop/usbcapture.txt
> 
> plugged in my device and run my code. I'm attaching all the
> information from the run and some other stuff that Alan and
> some other helpful people suggested could help to debug this
> issue.

Comments below.

> Xiaofan suggested deleting my modified udev rule, I tried this
> but then my device cannot be found at all by libusb.
> 
> Alan or someone else suggested something else too to set
> some debug flag or get some output but I can't find the mail
> which is strange as I never delete anything. If this rings
> a bell, please repeat what you suggested.

It was the usbfs_snoop parameter, which you did eventually remember.

> Over to you guys, what should/could I try next?
> 
> I'm sort of getting the feeling that this might be an
> issue with Ubuntu.

I don't think so.  More likely it's a bug in the Java bindings for
libusb.

> Output from sudo cat /sys/kernel/debug/usbmon/0u 

The initial part shows your device being plugged in; it isn't
important.  I'll skip directly to the part where you ran your program:

> dd0e0600 806429271 S Co:2:004:0 s 00 09 0000 0000 0000 0
> dd0e0600 806431484 C Co:2:004:0 0 0

This is the Set-Configuration request.  The trace shows that the config
was set to 0, not 1.

...
>         USB_dev_handle dev = usb_open(device);
>         assertOk(dev != null ? 0 : NON_STD_ERR, "usb_open");
> 
>         ret = usb_set_configuration(dev, 1);
>         assertOk(ret, "usb_set_configuration");

Since your program tried to set config 1, the simplest conclusion is
that the 1 got changed to 0 somewhere between your program and the
kernel.  Most likely in the libusb bindings.

>         //ret = usb_detach_kernel_driver_np(dev, 0);
>         //assertOk(ret, "usb_detach_kernel_driver_np");
> 
> 
>         ret = usb_claim_interface(dev, 0);
>         assertOk(ret, "usb_claim_interface");

I suggest you work around this bug by getting rid of the 
usb_set_configuration() call and adding back the 
usb_detach_kernel_driver_np() call.

Alan Stern