Forcing re-enumeration of a chosen USB device from userspace?

Hi,

I have a buggy USB device which works fine if connected before booting Linux and also starts to work if I unbind and rebind the XHCI driver.

On the other hand, hot plugging the device with the driver already running usually results in invalid descriptors being returned and sometimes even if the descriptors are right, the device still doesn't function entirely normally. I suspect a race between initialization of its internal state and enumeration by the host, nothing I can fix.

Rebinding XHCI driver forces new enumeration of the device and reliably fixes all issues every time, but it has the obvious downside of also resetting everything else on this bus.

Can I have the same effect selectively, for one chosen device only?

You can reset the device by using the usbreset program, which is part of the usbutils package. Some distributions (such as Ubuntu) include it whereas others (such as Fedora) don't. But if you don't have it, you can get the source code from https://github.com/gregkh/usbutils/
and build it yourself.

If the reset causes some descriptors to change, the kernel will re-enumerate the device.

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You can reset the device by using the usbreset program, which is part of the usbutils package. Some distributions (such as Ubuntu) include it whereas others (such as Fedora) don't. But if you don't have it, you can get the source code from https://github.com/gregkh/usbutils/
and build it yourself.

If the reset causes some descriptors to change, the kernel will re-enumerate the device.

Thanks for the suggestion. I compiled the tool fom Greg's repository and ran it 100 times in a loop, but the descriptors remained unchanged.

I only got "reset USB device" messages in dmesg and class driver noise.

I had no luck playing with sysfs entries of the device, but I found that the parent hub allows me to disable/enable individual ports. There is some subtlely in USB 3.0 as the associated 2.0 port must be disabled first to prevent downgrading to high speed, but it works.

Curiously though, it doesn't have the same effect as reloading the host driver. My buggy device randomly comes back with good descriptors, with the same bad descriptors, or most often it doesn't come back at all.