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    SubjectRe: xpad input driver: Xbox 360 Wireless Adapter
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    Hi

    I'm not very familiar with the xbox-gamepad driver, but please see
    below for some comments:

    On Mon, Sep 23, 2013 at 2:34 AM, Zachary Lund <admin@computerquip.com> wrote:
    > I'm apologize ahead of time if this thread isn't appropriate, I'm not
    > very familiar with mailing lists, especially lkml. I'm also very new
    > to kernel/module development (as of literally yesterday).

    Input-drivers are discussed on <linux-input@vger.kernel.org> (now
    CC'ed). I recommend subscribing to that list. I also put some driver
    developers on CC as they are probably more qualified to answer your
    questions.

    Note that LKML is a high-traffic list mostly used in CC. Please always
    CC the driver authors or maintainers.

    > I was looking into getting the LED working properly for the Xbox 360
    > controllers and learning about the basics of a kernel module at the
    > same time. There were a few things that confused me. I will reference
    > functions by name and all functions are from the current 3.12 branch.

    It might be useful to mention the driver in question (it's
    drivers/input/joystick/xpad.c I guess?).

    > First, xpad_send_led_command seems to be geared only towards the
    > "Microsoft X-Box 360 pad". Using xboxdrv as a reference, they use a
    > completely different packet structure to set the LED status on the
    > wireless controller which can be seen here:
    > https://github.com/Grumbel/xboxdrv/blob/master/src/controller/xbox360_wireless_controller.cpp#L66

    I don't think the kernel driver supports wireless pads, so it might
    have a different "wireless optimized" wire-protocol. The driver is
    USB-only, isn't it?

    > Second, the driver acts strangely when setting the LED. It calls
    > xpad_send_led_command during xpad_led_probe during xpad_probe but
    > there's a chance that a controller might not even be connected if
    > using the wireless adapter during that time!

    What? During xpad_probe() a device must be fully functional. What
    adapter are your talking about?

    > The only way to seemingly
    > tell if a controller is connected is by receiving the correct
    > connection packets. If I use the correct packet structure (which I
    > ripped almost directly from xboxdrv) and set the led after parsing a
    > connection packet, the LED seemingly works fine!

    Sounds reasonable. Do all devices send the connection-packets? If yes,
    feel free to send a patch which moves LED initialization after receipt
    of this package.

    > Third, I'm incredibly new to really low level development. Whenever
    > loading the module, it finds my wireless adapter but then creates 4
    > devices (which seems to mean only 4 controllers are allowed per
    > wireless adapter), each of which cause a call to xpad_probe. I
    > couldn't figure out how to tell if other wireless controllers were
    > already connected to the wireless adapter so I could light up the
    > correct LED. How would I go about this properly?

    Ugh? Sorry, but I don't understand what kind of wireless adapter this
    is? Please give us a bit more information here. If the device is a
    Bluetooth-device, why use an adapter at all?

    Cheers
    David


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