XInput and HID - architecture

[Aric Stewart]

On 3/3/16 7:52 AM, Juan Jose Gonzalez wrote:
> Thanks for your input.
> 
> On 03/03/2016 02:14 PM, Aric Stewart wrote:
>> The registry?
>>
>> Would you be able to load mappings from the registry?
> Sorry, I should have mentioned that. I was planning on storing the
> mappings in the registry in all three proposed solutions. My question
> was where to put the code that does the serialization and deserialization.

Why store the mapping serialized?  I think it would be far better to have the mapping be very clear and user editable in the registry. 

Something like, this is just off the top of my head...

HKCU/Software/wine/Xinput/mapping/<VIDPID>/BTN_A
Page=0x9
Usage=0x1
Released=0x0
Pressed=0x7fff
Logic="VAL_TO_BTN_GT_ZERO"

HKCU/Software/wine/Xinput/mapping/<VIDPID>/BTN_B
Page=0x9
Usage=0x2
Released=0x0
Pressed=0x7fff
Logic="VAL_TO_BTN_GT_ZERO"

HKCU/Software/wine/Xinput/mapping/<VIDPID>/LTHUMB_X
Page=0x1
Usage=0x30
Inverted=0

HKCU/Software/wine/Xinput/mapping/<VIDPID>/LTHUMB_Y
Page=0x1
Usage=0x31
Inverted=1

Then a complete mapping would be required to have all the elements defined. And it would just be the process of loading the values from the registry to build your mapping. 

I think that would be much cleaner than trying to store serialized mappings into the registry. 

It also may be my imagination but I could have sworn that a linux user once told me that there is a big database of gamepad mapping for xbox controllers somewhere out there. If that does actually exist it would be convenient to be able to access that.

We do some mapping like this for dinput on linux already where in HKCU\Software\Wine\DirectInput you can setup <joystick name> = <axes mapping>

(https://wiki.winehq.org/Useful_Registry_Keys)

I think that would be insufficient for what you need, but has the spirit of what I feel like we should do.

-aric


>>
>> Then you could have a .cpl that allows a user to produce mappings for their controller, likely tagged by VendorId and ProductId, and then Xinput can load those mappings from the registry.
>>
>> I think that is the cleanest and easiest way to store those. I would say something in HKCU/Software/wine/Xinput.
>> I would venture so far as to say that even the default mapping for the Xbox controller could be maintained there, so that the default mapping can be overridden, because it is likely that the xbox controller on the Mac and the xbox controller on Linux may have different controller mappings, and on mac it may even vary based on what xbox controller driver the user has installed, though there is a single prominent one that most people have.
> I planned to do binary serialization/deserialization, so manually
> creating registry entries would be a bit difficult. The idea was to ship
> some default mappings defined in the code and compiled into xinput, and
> allow new mappings and overrides from the registry. Those would have to
> be created with a tool (xinput.cpl). Of course, that tool can also be
> used to define the default mappings, we'd just have to get the generated
> binary blob into wine.
>>
>> So this would be your option 2, using the windows registry as the separate logic.
> The problem is that I need somewhere to put the code that does the
> serialization/deserialization. It's quite simple as long as the
> configuration can be stored as a binary blob, but it's still not
> trivial. If possible, I would like to avoid duplicating the code, hence
> the need for a common module.
>>
>> -aric
>>
>> On 3/3/16 2:39 AM, Juan Jose Gonzalez wrote:
>>> Hi,
>>>
>>> I got a bit stuck and would like to hear your opinion on the XInput HID backend, specifically on the mappings, i.e. the code that "accepts" a certain device based on its properties and then maps its buttons and axes to XInput buttons and axes.
>>>
>>> As long as the mappings are fixed, i.e. are not supposed to be extended or edited by the user, everything can be compiled into xinput1_3.dll. However, I would like to provide a "xinput.cpl" control panel node for xinput similar to "joy.cpl", where the user can not only test the XInput gamepads, but also manage the XInput-HID backend mappings. The first part can be accomplished by using xinput1_3.dll. However, in order to load and persist different mappings, the second part requires access to the functions that serialize and deserialize the mappings. It also needs some way of getting raw capabilities and changes in HID devices in order to be able to create new mappings.
>>>
>>> Here are some possible ways of solving it:
>>>
>>>    * Extend xinput1_3.dll with the required management functions and add a "wine/xinput_hid_mgmt.h" or similar header that declares those methods. xinput.cpl could then simply use xinput1_3.dll to perform all management functions. I'm not sure if this would break anything due to the additional exports in the dll.
>>>    * Extract the mapping load and store logic into a separate "xinputhid.dll" or similar. I this case both xinput1_3.dll and xinput.cpl would access this library to load and store mappings.
>>>    * Move the xinput core and backends into a driver and let xinput1_3.dll access it via IOCTLs. I believe this is the way it works on windows, although there doesn't seem to be any freely available documentation regarding the internal architecture. The XInput-HID backend could then create its own kernel object as a management interface, which could be accessed by xinput.cpl. This would have the added effect of having a single instance managing the xinput devices if several programs are running at the same time, which mimics the behavior of windows.
>>>
>>> What do you think would be the best option? Is there another way I haven't mentioned?
>>>
>>> - Juan
>>>
> - Juan
>