Re: X: SampleUSBMIDIDriver / SetConfiguration question

• Subject: Re: X: SampleUSBMIDIDriver / SetConfiguration question
• From: Laurent Humbert <email@hidden>
• Date: Fri, 20 Sep 2002 21:37:57 +0200

At 7:36 PM +0200 9/20/02, Laurent Humbert wrote:

(he replies to his own question)

Problem solved. The SampleUSBMIDIDriver does a

	LoadDescriptor(kUSBStringDesc, 0, 0, buf, sizeof(buf));

even though the device does not support strings (index == 0 in the device descriptor), and this (justifiably ?) unexpected request upsets the firmware.

That looks like its trying to get string descriptor zero.

If the device did implement any string descriptors at all, ie any of the string index fields in the other descriptors are non zero, it must respond to this request. This is a request for the table of supported language IDs.

As the device does not implement any string descriptors at all, a STALL would be a more appropriate response from the device, however in this circumstance the host should not be asking for the descriptor. I always put more weight on host behaving properly, but the device is not exactly correct.

A STALL response would have made things much more obvious than a non response.

Cheers;

Laurent
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