I'm looking at the trace from the HID keyboard application (under Windows 2000 & XP), and am seeing some anomalies. I hope someone else knows what is going on here. Everything looks good up through the Addressed state. But durring the get descriptors phase there are some string requests that seem out of place.

What are those get string requests doing interupting the get configuration descriptor request??? From what I understand it is normal for the host to ask for the first 9 bytes of the configuration descriptor (to determine the length of the full configuration descriptor), followed by reqesting the complete descriptor. But why are strings being requested in the middle of this process?

Why is the host asking for something that is supportted by only high speed devices? Shouldn't the host know that this device is not a high speed device? That should be known before entering the default state.

Here are those pesky string requests again. And they are requested twice. From here on everything appears "normal". (i.e. after setting the device address, the host asks for the device and configuration descriptors before loading a driver and setting the configuration.

Can someone explain why the string requests are interupting this phase of the enumeration? And why are there multiple requests for the same descriptors???

- Joe

Hi jdupre,

Unfortunately, the inner working of Windows USB drivers is not very clear.
It seems that the Qualifier Descriptor is requested from full-speed devices by the Windows XP driver but not by the Windows 2000 one.
I cannot give you an answer about the rationale behind requesting the various String descriptors multiple times.

Regards.

Although thread is quite old, decided to answer it (Google may lead you here):

Call for descriptor 0x06 simply happens. It is completely valid to answer this request with a STALL, because low and full speed devices do not have to answer it.

Also, before a string descriptor is queried, there seem to be a string 0 descriptor request before (language descriptor).
If you have a look at LibUSB-win32, there are two calls, which request a string: one with an additional language id parameter, and another one without this parameter, which fetches language before fetching the string. Maybe these calls are similar to some Windows USB library calls.