[Pcsclite-muscle] usbfs: process %d (pcscd) did not claim interface 0 before use

[Ludovic Rousseau]

Le ven. 10 juil. 2026 à 17:42, Sebastien Lorquet
<sebastien at lorquet.fr> a écrit :
> I had not test that before, but I just noticed that the message flood stops when the reader is not attached to virtualbox!
>
> So to reproduce it, you can just start a virtualbox vm and attach the device to the vm.
>
> My virtualbox version is 7.1.18 r173720

I installed virtualbox-7.2 7.2.12-174389~Debian~trixie
I created a VM with Debian 13 installed in it.

I can reproduce the problem.
It happens when the reader is already used on the host.
This is expected since the reader can't be used by 2 different pcscd processes.

> It might be a virtualbox issue! But I have no idea why!

Virtualbox is "stealing" the reader from the host. And the pcscd
running on the host is not notified.
All it gets are libusb errors:
00000069 [140198007875264] ../src/ccid_usb.c:963:WriteUSB() write
failed (3/7): LIBUSB_ERROR_IO

> I also noticed that the reader is still visible to pcscd, even when the reader is attached to the VM. So there is some complex interaction here.

Yes. And that is the source of the problem.

If you always attach the same reader to the VM, I suggest to ignore it
for the pcscd on the host.
You can use PCSCLITE_FILTER_IGNORE_READER_NAMES in /etc/default/pcscd.
see https://blog.apdu.fr/posts/2015/12/remove-andor-customize-pcsc-reader-names/
or PCSCLITE_IGNORE in a udev rule file. see
https://blog.apdu.fr/posts/2025/04/ignore-readers-using-pcsclite_ignore-udev-property/

Another solution is to first attach the reader to the VM and then
start pcscd on the host.
pcscd on the host will then get:
00000039 [139956558777792] ../src/ccid_usb.c:681:OpenUSBByName() Can't
claim interface 3/7: LIBUSB_ERROR_BUSY
and will ignore the reader.

Bye

--
 Dr. Ludovic Rousseau