Re: [Libusb-win32-devel] application works with older libusb-win32 but not with version 0.1.12.1

[Graeme G. <gr...@ar...>]

Dan Ellis wrote:
> Having a configuration descriptor with a value of zero is very broken - 
> there is no way to select it. When the host issues SET_CONFIGURATION 
> with wValue = 0, to select that configuration, the device should enter 
> the low power state, and the host should assume that the device has no 
> active endpoints.
> 
> The library doesn't have  a coherent way of dealing with a device with a 
> configuration with value zero, since it keeps track of which endpoints 
> are valid to send data on.
> 
> What would be your suggestion for a solution?

I would imagine that the simplest thing may be to assume that the
descriptor is in error, since (from what you say), it would make
no sense for a device to actually have a maximum configuration
value of 0.

The sort of thing I've done in such cases (dealing with broken
implementation of standards) is to have a configurable "forgiving"
mode, with appropriate debug messages being available to track
what's going on.

So with libusb set to a "try and correct broken configuration desciptors"
mode, it would internally treat a configuration descriptor with a value of zero
as a value of 1, which (I would guess), might solve the original posters
problem.

Graeme Gill.