GetName() creates a new evdev device which calls tons of ioctls. But the
main culprit is close() which for input devices appears to be a slow
path in the kernel.
This commit reduces PopulateDevices() by 50% on my laptop, but ~730 ms
is still ridiculously slow for something that isn't needed right away.
The SDL backend crashes when you close a joystick after SDL_Quit has
been called. Some backends don't need to be shutdown and
re-initialized everytime, we can just ask to enumerate devices again.
This adds hotplugging support to the evdev input backend. We use
libudev to monitor changes to input devices in a separate thread.
Removed devices are removed from the devices list, and new devices
are added to the list.
The effect is that controllers are usable immediately after plugging
them without having to manually refresh devices (if they were
configured to be used, of course).
This makes the device ID assigning code common to all backends, by
moving it to AddDevice() instead of copy-pasting or replicating
the logic in the backends.
Also, to prepare for hotplugging, instead of relying on a name usage
count, the new ID assigning system always starts from ID 0 and tries
to assign the first ID that is not used.
The values are expected to be in the 0.0-1.0 range (as indicated by the
comment), and other parts of Dolphin also expect it to be in that range
since the "full" axis has a -1.0 to 1.0 range. However, this is not
always the case and fvalue can end up being outside of the range. This
clamps fvalue to always be in the 0.0 and 1.0 range.
Small cleanup by using std::shared_ptr and getting rid of
ciface.Devices() which just returned the m_devices (which defeats the
point of making m_devices protected).
Incidentally, this should make the code safer when we have
different threads accessing devices in the future (for hotplug?).
A lot of code use Device references directly so there is
no easy way to remove FindDevice() and make those unique_ptrs.
Previously, the devices vector would be passed to all backends. They
would then manually push_back to it to add new devices. This was fine
but caused issues when trying to add synchronisation.
Instead, backends now call AddDevice() to fill m_devices so that it is
not accessible from the outside.
Tillmann Karras