Re: using devel/libusb to access USB

From: Toni Andjelkovic (toni_at_soth.at)
Date: 11/25/03

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    Date: Tue, 25 Nov 2003 10:53:29 +0100
To: Dan Langille <dan@langille.org>

    On Mon, Nov 24 2003 (09:25:52 -0500), Dan Langille wrote:
    > We have been looking at the devel/libusb port and experimenting with
    > testlibusb which is a part of that port. We have noticed that
    > usb_find_devices() does not find any devices. Looking at the usb.c
    > code within libusb, we found that usb_os_find_devices() does not
    > return any devices, and therefore the while loop is never entered.
    >
    > We tracked the problem down to usb_os_find_devices() (within bsd.c)
    > and found that various things were preventing the list from being
    > created.

    I have experienced a similar problem a few months ago. I've tracked
    it to ugenopen() in sys/dev/usb/ugen.c, which returned EBUSY if
    the control endpoint /dev/ugen0 was already open. Consequently,
    usb_find_devices() failed to return anything useful.

    However, as Bernd Walter suggested in a recent posting to hackers@,
    this could be avoided by using interface specific endpoints (/dev/ugen?.?)
    instead of the control endpoint (/dev/ugen?) for communication.

    Cheers,
    Toni
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