Claim interface on different handles to the same device fails

[Lederhilger M. <M.L...@ds...>]

Hello,

I am a user of the PointCloudLibrary, which uses OpenNI to communicate
with a Kinect like USB-device (point cloud capture device). I use Linux
as an operating system. If I use the XnSensorServer then everything
works, so my following question is more out of curiosity:

If I do not use the XnSensorServer, then OpenNI's sensor driver uses
'libusb_open' and 'libusb_claim_interface' multiple times on the same
device (for depth-, infrared- and RGB-imagegenerator). Each call to
'libusb_open' returns a different handle - so the first
'libusb_claim_interface' passes, but the second one fails with an error,
that the device is already claimed because 'claimed_interfaces' (used to
block the call to OS specific claim interface function, if the device
has already been claimed by this function - see
'libusb_claim_interface') is stored in the handle's and not in the
device's data structure.

So my question is that if it is legal (from libusb's point of view) to
open one device multiple times. If yes, then would not it be better to
store 'claimed_interfaces' in the device instead of it's handle. Since I
am new to this matter, maybe you can give me some insight on this.

Thank you,

Martin Lederhilger