[libhid-discuss] device with multiple interfaces

[Charles Lepple]

On May 19, 2007, at 6:34 AM, Arvid Picciani wrote:

>           Report Descriptor: (length is 36)
>             Item(Global): Usage Page, data= [ 0x00 0xff ] 65280
>                             (null)
>             Item(Local ): Usage, data= [ 0x01 ] 1
>                             (null)
>             Item(Main  ): Collection, data= [ 0x01 ] 1
>                             Application
>             Item(Local ): Usage Minimum, data= [ 0x01 ] 1
>                             (null)
>             Item(Local ): Usage Maximum, data= [ 0x08 ] 8
>                             (null)
>             Item(Global): Logical Minimum, data= [ 0x00 ] 0
>             Item(Global): Logical Maximum, data= [ 0x01 ] 1
>             Item(Global): Report Size, data= [ 0x08 ] 8
>             Item(Global): Report Count, data= [ 0x3c ] 60
>             Item(Main  ): Input, data= [ 0x02 ] 2
>                             Data Variable Absolute No_Wrap Linear
>                             Preferred_State No_Null_Position  
> Non_Volatile
> Bitfield

60 bytes of input, apparently

>             Item(Local ): Usage Minimum, data= [ 0x01 ] 1
>                             (null)
>             Item(Local ): Usage Maximum, data= [ 0x08 ] 8
>                             (null)
>             Item(Global): Logical Minimum, data= [ 0x00 ] 0
>             Item(Global): Logical Maximum, data= [ 0x01 ] 1
>             Item(Global): Report Size, data= [ 0x08 ] 8
>             Item(Global): Report Count, data= [ 0x3c ] 60
>             Item(Main  ): Output, data= [ 0x02 ] 2
>                             Data Variable Absolute No_Wrap Linear
>                             Preferred_State No_Null_Position  
> Non_Volatile
> Bitfield

and 60 bytes of output. The "Usage Minimum" and "Usage Maximum" part  
is a little odd, and that will probably confuse the hidparser code in  
libhid.

You may be better off using libusb calls directly after opening the  
2nd interface.

-- 
Charles Lepple
clepple at ghz.cc