[libhid-discuss] USB - HID query

[Charles Lepple]

On Apr 18, 2007, at 2:00 AM, Anmol Ranka wrote:

> It is compound device because, it consists of two different devices  
> embedded
> within a single device through a hub.

 From a programming standpoint, the "compound device" distinction is  
not important, because it should show up as two separate devices in  
the USB API.

> It is a composite device because within the same device, there are two
> functionalities i.e they same device belongs to audio as well as  
> HID class.

You can specify which interface to open.

> I downloaded the following package 'libhid_0.2.15 
> +20060325-2.1.tar.gz'. Is it
> OK to use this package for Fedora Core 5?

It hasn't been tested with Fedora specifically, but a few people have  
reported success.

> If yes, when I install this
> package, what will be the name of the libhid library that I have to  
> use and
> in which location would it be installed?

You can specify the location by passing --prefix= to ./configure. The  
library name is libhid.so.

> I also have following query:
>
> 1)To perform input and output operation, I need 'HID usage path'.  
> If I am
> right the HID Usage path is obtained from the HID Report  
> Descriptor. In order
> to know the HID report descriptor I executed the following command  
> provided
> by libhid:
>
> lsusb -d VID:PID -vvv.
>
> The partial output of this command is as follows.
>
> HID Device Descriptor:
>           bLength                 9
>           bDescriptorType        33
>           bcdHID               1.11
>           bCountryCode            0
>           bNumDescriptors         1
>           bDescriptorType        34 Report
>           wDescriptorLength     172
> cannot get report descriptor
>
> Why is the report descriptor not printed?

The kernel usbhid driver is probably still connected to that interface.

-- 
Charles Lepple