Re: [Libusb-devel] Getting error 22 when writing to interrupt EP using HID API

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

On Thu, 22 Mar 2012, Petr Medek wrote:

> > You misunderstand what the error code means.  This has nothing to with
> > the device's behavior.  Rather, your interrupt transfer is not accepted
> > in the first place, because something is wrong with it.  Incorrect
> > endpoint number or something like that.
> >
> > Alan Stern
> >
> 
> That was exactly my idea and that's why I asked for help, because I
> can no see anything wrong.
> 
> My device description says, it has interrupt OUT EP with address 0x02
> (http://usb.medek.info/info.txt)
> 
> In my code I just trigger:
> 
>   result = libusb_interrupt_transfer(
>        devh,
>        INTERRUPT_OUT_ENDPOINT, // this is 0x02
>        outData, 9,
>        &bytes_transferred,
>        TIMEOUT_MS);
> Full code e.g.  http://usb.medek.info/test1.c.html
> 
> Is there any way I can find out what's the invalid call I do? Some
> trace in usblib or usb device?

You can turn on the usbfs_snoop flag before running your program and 
then see what shows up in the dmesg output:

	echo 1 >/sys/module/usbcore/parameters/usbfs_snoop

Alan Stern