[PATCH v3] winebus.sys: Handle device reports for hidraw devices

[Sebastian Lackner]

On 21.10.2016 05:39, Aric Stewart wrote:
>>> 
>>> Another idea we could consider (at least for Linux) would be to
>>> use wine_server_fd_to_handle(), and then NtReadFile(). This would
>>> allow to get rid of the thread, and we could use an APC to run
>>> IoCompleteRequest(). Have you actually looked into that? And
>>> which mechanism is required on other platforms, do they also
>>> require a separate thread?
>>>
>
> I have not explored wine_server_fd_to_handle as I was not really
> aware of it, Mac and IOHID uses a callback, so a run loop thread is
> needed, but no read of any sort.  If you thinking doing that wine
> magic is correct then I would be up for exploring it, but it seems
> like the sort of thing that Alexandre would frown on.
> 
> -aric

Well, using async NtReadFile would have the advantage that we can
start listening for reports at any time, without spawning a thread.
Nevertheless, if other platforms do not offer some similar mechanism,
it probably does not make any sense to implement it like that. I'm
also fine with a thread based approach.

I would still suggest to do further investigations regarding report
loss though. If there is not sufficient evidence that this happens
on Windows aswell, I would still prefer a more reliable Wine
implementation. MSDN suggests that in order to avoid dropped HID
reports, applications can try to increase HidD_SetNumInputBuffers -
but that will obviously not help if we already drop them in the
lower level drivers. The idea with a simple flags only works if we
can be sure that the thread runs fast enough to ensure records
are never dropped. Otherwise a more complicated approach would be
required.

Regards,
Sebastian