Re: [PATCH 1/1] Input: xpad - update docs to reflect current state

[Daniel Dressler]

Thanks Jon

I've sent a second version of the patch without the TODO list edits.


Now I would like to ask about a backwards compact issue related to this driver.

Eons ago in patch 99de0912b [0] when support for the wireless 360
controllers were added the decision was made to map their Dpad to the
discrete buttons.

There is reasonable justification for this behavior since the Dpad has
never functioned like an analog stick on Xbox hardware.

Except support for wired 360 controllers had been added a year earlier
and used the opposite behavior. In fact the wireless 360 controllers
are the only controllers which use the dpad_to_button behavior.

Original Xbox, wired Xbox 360, and all Xbox One controllers all expose
the dpad as a set of axises.

This has caused pain for downstream developers. It means two
controllers  have wildly different behavior. Many developers have just
ignored the issue or suggested users unload xpand and use the userland
replacement. Even Arch's wiki suggests such [1]. Which to be honest is
all one can do. The xpad driver does not expose the information
developers need to even incorporate a workaround without nasty hacks.

As a downstream developer I've been bitten by this twice. The first
time I didn't even know that wired vs wireless made a difference and I
was disturbed to learn the truth.

So here is what I want to hear opinions on: should the wireless 360's
dpad be exposed as both axises _and_ buttons?

[0]: https://github.com/torvalds/linux/commit/99de0912b when t
[1]: https://wiki.archlinux.org/index.php/joystick#Xbox_360_controllers

Daniel

2014-11-08 3:48 GMT+09:00 Jonathan Corbet <corbet@xxxxxxx>:
> On Mon,  3 Nov 2014 17:53:06 +0900
> Daniel Dressler <danieru.dressler@xxxxxxxxx> wrote:
>
>> The last time this documentation was accurate was
>> just over 8 years ago. In this time we've added
>> support for two new generations of Xbox console
>> controllers and dozens of third-party controllers.
>>
>> This patch unifies terminology and makes it explicit
>> which model of controller a sentence refers to.
>
> So this seems like a useful update, and I was looking at pulling it into
> the docs tree.  But this hunk:
>
>> diff --git a/drivers/input/joystick/xpad.c b/drivers/input/joystick/xpad.c
>> index 2ed7905..7e2e047 100644
>> --- a/drivers/input/joystick/xpad.c
>> +++ b/drivers/input/joystick/xpad.c
>> @@ -40,8 +40,8 @@
>>   *
>>   * TODO:
>>   *  - fine tune axes (especially trigger axes)
>> - *  - fix "analog" buttons (reported as digital now)
>> - *  - get rumble working
>> + *  - add original xbox rumble pack support
>> + *  - add xbox one rumble support
>>   *  - need USB IDs for other dance pads
>>   *
>>   * History:
>
> Seems like a different change that shouldn't be mixed up with the doc
> update.  Send me a version without that change and, in the absence
> of complaints, I'll apply it.
>
> Thanks,
>
> jon
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/