Re: [Libusb-devel] Receiving interrupt transfer packets

[Alan S. <st...@ro...>]

On Tue, 20 Jul 2010, Nikolai Kondrashov wrote:

> > How do you envision the tool working?
> Do you mean the "wizard" tool or hid-dump? Anyway, here is the plan.
> 
> The hid-dump does the usual libusb setup like opening device, detaching and
> claiming interfaces. It finds all the HID interfaces of the specified device
> or just uses the specified one. Then it should send Set_Idle request with
> wValue set to zero to specify that any reports should be sent when and only
> if the state is changed. After that it should dump whatever is received via
> interrupt IN endpoints to stdout continuously. It should also support output
> pausing/resuming with, say, SIGUSR1/SIGUSR2. It already supports report
> descriptor dumping to some extent.

I get it.  Then the answer to your original question is easy: You don't 
need to worry about parsing report descriptors, variable report 
lengths, or anything else.  Simply transfer individual maxpacket-sized 
buffers and dump whatever you get.  All reports (except possibly the 
longest) will terminate with a short packet.  In any case, the hid-dump 
program wouldn't need to parse the reports or determine their 
boundaries.

Alan Stern