[PATCH 1/5] winebus.sys: Handle linux input event device via udev

[Aric Stewart]

On 2/27/17 10:52 AM, Sebastian Lackner wrote:
> On 27.02.2017 17:22, Aric Stewart wrote:
>> On 2/27/17 10:00 AM, Sebastian Lackner wrote:
>>> I assume this is meant as a fallback, if we don't have access to
>>> hidraw, right? If you plan to use this as a replacement for dinput,
>>> it would be better to implement it without fixed dependency on
>>> udev.
>>>
>> Likely users using HID for gamepads and joysticks will end up this
>> route by default because all the permissions are automatically setup
>> for us. Also then user will get to leverage all the work done in the
>> kernel to handle devices that do not behave well on the HID side or
>> which do not show up at all using hidraw (Xbox Controllers for
>> example)
>>
>> The dependency for udev is for common device discovery. I feel like I
>> still want that dependency unless we write our own device plug and
>> unplug discovery system.
> 
> Are you sure that there are no systems out there where we have linux
> events, but no udev? If yes the current solution is fine, but otherwise
> we should at least implement a fallback method similar to how its done
> in dinput (basically, just trying to open all devices in the range 0 ..
> MAX_JOYDEV).
> 

I am not a linux expert but according to quick web research udev has been default since about Linux kernel version 2.6.13. That is sometime around 2006. It became part of systemd in 2012. So I am reasonably sure that any modern linux system will have it. I am not sure how much we worry about pre 2006 systems. 

-aric


>>> Does it hurt when both hidraw and input event devices are found? If
>>> yes, it would be better to filter duplicates somewhere else,
>>> instead of using registry keys.
>>>
>> You can get duplicate devices, on being talking to the hidraw device
>> and one to the linux event device, but both are the same physical
>> device. I have explored a little bit to try to find if there is a
>> good way to detect if a device is duplicated but it has not proven to
>> be immediately easy.
> 
> If it can cause problems it is probably still worth the effort. There
> might also be systems where hidraw devices have access permissions by
> default, and we don't want to get duplicated input events then.
> 
>> Also then the question because which device is
>> preferred if we find a duplicate.
>>
> 
> I think preferring hidraw might be slightly better. Some devices also
> offer their own control utilities, and those would probably not work when
> using linux input events. Nevertheless, its a matter of taste and we can
> certainly discuss about that.
> 
> Best regards,
> Sebastian
>