Implement detach_and_claim_interface

[bugadani]

Closes #34

Interestingly, the PR needs the fallback-to-racy code, otherwise it's not working on my ubuntu which is definitely not 12 years old (I'm getting "this ioctl is not valid for this device" error). Not sure what's going on there, maybe it's an undiscovered bug in libusb which I used as the source to port this code from. Or maybe I just can't copy code very well, as the number of force pushes here indicates :)

[kevinmehall]

This seems backwards -- you want to detach a kernel driver (e.g. ftdi_sio), but don't want to detach another instance of nusb / libusb using usbfs.

[bugadani]

Monkey see this, monkey do !=. Monkey no think source is C and that strcmp returns 0 if equal :)

[kevinmehall]

Interestingly, the PR needs the fallback-to-racy code, otherwise it's not working on my ubuntu which is definitely not 12 years old (I'm getting "this ioctl is not valid for this device" error).

It's actually the opposite for me (Ubuntu 22.04, Kernel 6.5.0). The USBDEVFS_DISCONNECT_CLAIM is working, but the USBFS_GETDRIVER and USBFS_IOCTL calls (which also affects reattaching) are failing with ENOTTY ("Inappropriate ioctl for device"). Are you sure that's not what you're seeing?

Those weren't working because the ioctl opcodes were wrong -- the rustix ioctl::ReadOpcode, ioctl::WriteOpcode, ioctl::ReadWriteOpcode corresponds to the _IOR, _IOW, _IOWR etc in https://github.com/torvalds/linux/blob/master/tools/include/uapi/linux/usbdevice_fs.h. That opcode type is arbitrary and doesn't necessarily correspond to the ioctl::patterns type used or direction of actual data flow. I pushed some commits including fixing these.

Can you re-test with RUST_LOG=debug and see if you're getting the USBDEVFS_DISCONNECT_CLAIM ioctl failed, falling back to detach-then-claim debug!() I added in the fallback code path?

[bugadani]

the rustix ioctl::ReadOpcode, ioctl::WriteOpcode, ioctl::ReadWriteOpcode corresponds to the _IOR, _IOW, _IOWR etc

Apparently I see something and write something else :) I promise usbdevice_fs.h was my source, not sure how I got those wrong :)

("Inappropriate ioctl for device")

I should stop reporting from memory.

Can you re-test

All I'm seeing is the following. I probably shouldn't be surprised, mine is also Ubuntu 22.04 with kernel 6.5.0.

DEBUG nusb::platform::linux_usbfs::device: Opening usbfs device /dev/bus/usb/001/006    
DEBUG nusb::platform::linux_usbfs::device: Opened device bus=1 addr=6 with id 0    
DEBUG nusb::platform::linux_usbfs::device: Detached and claimed interface 0 on device id 0

Thanks for touching up my silliness :)

[kevinmehall]

Dropped the fallback in the interest of not having legacy code that no one is testing, but if there comes a need for it, it'll be in git history.