Hello,

This is relating to my previous post "[edk2] Is this a right place to discuss EDK2's USB IF implementation?"
We found a mismatch between EDK2 source code and our USB vendor's implementation. Could you give us your opinions?


bInterfaceNumber , 9.6.5 Interface from Universal Serial Bus 3.1 Specification Rev 1.0 says;
--
Number of this interface. Zero-based value identifying the index in the array of concurrent interfaces supported by this configuration.
--


Regarding this.
EDK2 source code (UsbDesc.c) says:
--
//
// If a configuration has several interfaces, these interfaces are
// numbered from zero to n...
//
--


The USB vendor says:
--
* Numbering is not necessarily consecutive * Each interface can be independently turned on/off * Solution allows any combination of interfaces without re-defining the interface number * One general lookup table can tell you what interface is assigned to what interface number.
* For these reasons, the interface definition is like this on our products.
* The interface definition has remained the same from the previous products, and other products before that.
* Current interface numbering is supported by all Microsoft OS * Other PC OEM customers have never raised this issue
--

As a result, the vendor's USB IF looks like below.

===>Configuration Descriptor<===
...
bNumInterfaces: 0x02 <<<<
bConfigurationValue: 0x01
iConfiguration: 0x00
bmAttributes: 0xA0 -> Bus Powered
-> Remote Wakeup
...
===>Interface Descriptor<===
...
bInterfaceNumber: 0x0C <<<< Interface Number starts from 0x0C instead of 0. [comment from Yosuke]
bAlternateSetting: 0x00
bNumEndpoints: 0x01
...

===>Interface Descriptor<===
...
bInterfaceNumber: 0x0D <<<<
bAlternateSetting: 0x00
bNumEndpoints: 0x00
...


and it hits the following ON_ERROR in UsbDesc.c.
--
} else if (Setting->Desc.InterfaceNumber >= NumIf) {
DEBUG (( EFI_D_ERROR, "UsbParseConfigDesc: mal-formated interface descriptor\n"));

UsbFreeInterfaceDesc (Setting);
goto ON_ERROR;
}
--


What do you think the vendor's implementation?
Also, have you ever had such a USB IF mismatch between EDK2 and USB vendors before? If so, how are you handling such cases in general?

Kind regards,
Yosuke