Re: Random Interface numbers

On Fri, 31 Aug 2007 09:57:18 -0400 (EDT), Alan Stern <[email protected]> wrote:

> > T:  Bus=02 Lev=01 Prnt=01 Port=00 Cnt=01 Dev#=  8 Spd=1.5 MxCh= 0
> > D:  Ver= 1.10 Cls=00(>ifc ) Sub=00 Prot=00 MxPS= 8 #Cfgs=  1
> > P:  Vendor=1267 ProdID=0210 Rev= 0.01
> > S:  Product=PS/2+USB Mouse
> > C:* #Ifs= 1 Cfg#= 1 Atr=a0 MxPwr=100mA
> > I:* If#= 1 Alt= 0 #EPs= 1 Cls=03(HID  ) Sub=01 Prot=02 Driver=usbhid
> > E:  Ad=81(I) Atr=03(Int.) MxPS=   8 Ivl=10ms
> > 
> > usb 2-1: new low speed USB device using uhci_hcd and address 8
> > usb 2-1: config 1 has an invalid interface number: 1 but max is 0
> > usb 2-1: config 1 has no interface number 0
> > usb 2-1: configuration #1 chosen from 1 choice
> > input: PS/2+USB Mouse as /class/input/input8
> > input: USB HID v1.00 Mouse [PS/2+USB Mouse] on usb-0000:00:1d.1-1
> > 
> > I don't get it, why is max zero in this case?
> 
> In any configuration, the interface numbers must run from 0 to 
> bNumInterfaces - 1.  Hence if there is only one interface, its number 
> must be 0.

What do you think about this:

http://www.microsoft.com/whdc/system/bus/USB/USBFAQ_intermed.mspx
> Does Windows have requirements or guidelines for assigning numbers to multiple interfaces on a composite device?
> 
> A USB device with more than one interface on the first configuration is treated as a composite device. Windows XP (prior to Service Pack 2) mandates that interface numbers follow these rules:
> • Interface numbers must be zero-based.
> • Interface numbers must be consecutive and increasing.
> 
> Windows XP Service Pack 2 (SP2) relaxed the requirement that interface numbers be consecutive by making changes to the driver Usbccgp.sys. Beginning with SP2, interface numbers need only be increasing.
> 
> For additional information about interface numbers, see Microsoft Knowledge Base article 814560.
> 
> Windows has provided support for USB composite devices since Windows 98. The driver Usbhub.sys supports composite devices on the following operating systems:
> • The default value for an interface is always alternate setting zero.
> • Additional alternate setting numbers must be consecutive and increasing.
> 
> For additional information on alternate settings, see Section 9.6.5 of the USB 2.0 specification, which is available from the USB Web site at http://www.usb.org/developers/docs .

-- Pete

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