Re: libusb driver question: can't write to endpoint

On Sat, 10 Mar 2007, Phil Dibowitz wrote:

> So I sat down to start seeing if I could write the aforementioned driver for
> the Logitech Harmony remote using libusb. After reading the docs, I whipped
> out the following test code (ok, its mostly a copy and paste of the docs,
> but that's OK) which binds to the interface and attempts to do an interrupt
> transfer to the endpoint.
> 
> But I get: "error submitting URB: Bad address". I've attached the (very
> ugly) code below, but I don't think it's a coding error as much as a not
> understanding error.

Does that error string come from usb_strerror()?  My copy of libusb is
rather old and doesn't seem to include that routine.  It would help to see
the actual error code returned by usb_interrupt_write().

> Looking at lsusb, the device has one Configuration with bConfigurationValue
> 1, and one Interface with bInterfaceNumber 0.

Then why does your program try to claim interface 1?

> Under this interface, it has two endpoints, 0x81, "EP 1 IN", and 0x02, "EP 1
> OUT",

Actually that's EP 2 OUT, not that it matters.

> which I believe, from looking at USB Snoopy dumps, are IN ==>
> device-to-host, and OUT ==> host-to-device. But I've tried my code using
> both endpoints, and get the same error each time.
> 
> The USBSnoopy log shows from windows shows a very simple setup:
> SELECT_CONFIGURATION, CLASS_INTERFACE, GET_DESCRIPTOR_FROM_INTERFACE, and
> then a ton of BULK_OR_INTERRUPT_TRANSFERs. lsusb shows that the devices or
> of transfer type Interrupt.
> 
> Since all the software does is write a blob to the remote (which, after
> looking, turns out to just be XML), this all seems straight forward. It
> doesn't seem like I have to do any special setup...
> 
> The USBSnoopy logs show it writing 64 bytes at a time, so that's what I
> write in my code.

Your timeout value of 2 ms seems rather low.  You might want to increase 
it.

Have you tried setting the usbfs_snoop=1 module parameter for usbcore?  It 
will dump your program's I/O activity to the system log.

Alan Stern


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