Re: [Libusb-devel] How to reset (or re-enumerate) a USB device

[Peter S. <pe...@st...>]

Hi Paul,

Branham, Paul wrote:
> I have a custom USB device for which I developed a user-space API
> and demo program using libusb 0.1.12.

Note that libusb-0.1 is very old, unmaintained and deprecated.


> However, I really need it to work on my target platform - a Wind
> River Linux system.

What kernel is that system running? And LE or BE architecture?


> It almost does work, except that it won't work correctly until I
> manually hot plug the device. Before I do this, all URB requests
> time out.

This is strange. libusb can't really cause this, so either it's a
hardware/firmware problem, or something is amiss in that kernel.


> I can see the device with lsusb and open the device with libusb,
> but cannot send or receive data. Note:  usbmon shows no traffic on
> the USB bus.

Is there also no traffic when you first plug in the device?


> I have tried several things which I hoped would have the same
> effect as a manual hot-plug, but to no avail.

As far as software that communicates directly with the device goes,
there is indeed no complete equivalent of unplugging the device.

What you could do is hack the kernel hub driver to allow you to
disable power on the hub port that the device is connected to, wait a
bit, and then re-enable power. But this means you depend on a
modified hub driver.

In any case, this is not supposed to be neccessary, so there is
most likely a problem somewhere.


> Is there any reason to think that upgrading to the latest version
> of libusb would help with this problem?

I guess not, but it can't hurt to try, even if just for collecting
another data point.


//Peter