Thanks for the info.

On 2012.05.02 06:03, Xiaofan Chen wrote:
> Q5: When using interface control requests (LIBUSB_RECIPIENT_INTERFACE),
> WinUSB overrides the low byte of wIndex with the destination interface.
> Ref: http://www.lvr.com/forum/index.php?topic=331
>
> A5: this is so you only target your interface on a composite device. Letting a
> user mode stack manipulate a sibling interface is bad security and
> encapsulation, no?

Interesting.

I could have sworn I saw some documentation indicating that 
bmRequestType was supposed to be set to 0xC1 (=> recipient = interface) 
when attempting to retrieve the Extended Properties OS Feature 
Descriptor from a device. As a matter of fact, this is the info I 
currently provide on the WCID page [1]. However, checking on the latest 
MS documentation [2], it seems that Microsoft do state that it should be 
set to 0xC0 (=> recipient = device), in which case the WinUSB override 
does not occur.

I guess I'll have to update the xusb sample as well as the WCID page.

Regards,

/Pete


[1] 
https://sourceforge.net/apps/mediawiki/libwdi/index.php?title=WCID_devices#Defining_a_Device_Interface_GUID_or_other_device_specific_properties
[2] http://msdn.microsoft.com/library/windows/hardware/gg463182


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