Is this just general unused variable cleanup? I tend to do these small unrelated cleanups in separate patches. This way, the small cleanup gets its own commit and stays if your bigger patch needs to be reverted for whatever reason.

In the rest of your patch, you opened usbd_fd as a normal descriptor with O_RDONLY and now you're opening it as a directory descriptor. Maybe the rest of the usbd_fd open() calls should be updated to use O_PATH | O_DIRECTORY and I think you could eliminate most of the capabilities in your rights list for usbd_fd since I only see you using it for openat().

The fd returns from the openat will inherit all of the capabilities from the fd pass to openat. Therefore, for the /dev/usb/*.*.* devices, we should give the usbd_fd, READ, WRITE, EVENT, IOCTL for later usage.

I'd add a .Xr capsicum 4 here since you're mentioning it earlier.

These extern declarations aren't really doing anything since you declare both variables right below.

The extern declarations in dump.c should be enough. You could move them into a header and include that if you anticipate other source files needing to access them as well.

Oops, you're definitely right. Looks good to me then :)

You are right, I am too lazy:). Fix it now.