Dolphin has traditionally treated the SI IO buffer (128 bytes) as a set of
32 little endian u32s. This works out fine if you only ever read/write
using aligned 32bit accesses. Different sized accesses or misaligned reads
will mess it up. Byte swapping reads/writes will fix this up, but all the
SI devices that use the SI IO buffer need to be adjusted.
Currently, each player buffers their own inputs and sends them to the
host. The host then relays those inputs to everyone else. Every player
waits on inputs from all players to be buffered before continuing. What
this means is all clients run in lockstep, and the total latency of
inputs cannot be lower than the sum of the 2 highest client ping times
in the game (in 3+ player sessions with people across the world, the
latency can be very high).
Host input authority mode changes it so players no longer buffer their
own inputs, and only send them to the host. The host stores only the
most recent input received from a player. The host then sends inputs
for all pads at the SI poll interval, similar to the existing code. If
a player sends inputs to slowly, their last received input is simply
sent again. If they send too quickly, inputs are dropped. This means
that the host has full control over what inputs are actually read by
the game, hence the name of the mode. Also, because the rate at which
inputs are received by SI is decoupled from the rate at which players
are sending inputs, clients are no longer dependent on each other. They
only care what the host is doing. This means that they can set their
buffer individually based on their latency to the host, rather than the
highest latency between any 2 players, allowing someone with lower ping
to the host to have less latency than someone else.
This is a catch to this: as a necessity of how the host's input sending
works, the host has 0 latency. There isn't a good way to fix this, as
input delay is now solely dependent on the real latency to the host's
server. Having differing latency between players would be considered
unfair for competitive play, but for casual play we don't really care.
For this reason though, combined with the potential for a few inputs to
be dropped on a bad connection, the old mode will remain and this new
mode is entirely optional.
Normally, SI is polled at a rate defined by the game, and we have to send the pad state to other clients on every poll or else we'll desync. This can result in fairly high bandwidth usage, especially with multiple controllers, mostly due to UDP/IP overhead.
This change introduces an option to reduce the SI poll rate to once per frame, which may introduce up to one frame of additional latency, but will reduce bandwidth usage substantially, which is useful for users on very slow internet connections.
Polling SI less frequently than the game asked for did not seem to cause any problems in my testing, so this should be perfectly safe to do.
These aren't dependent on calling order so we can just organize all of the statics together
instead of splitting them up over the file. This also allows us to organize a common spot for
file static variables as well.
This lets Dolphin know if a configured GameCube Controller should actually
be treated as connected or not.
Talked to @JMC47 a bit about this last night. My use-case is that all of
my controllers are the same hardware (Xbox One controllers) so share the
same configuration (modulo device number). Treating them all as always
connected isn't a problem for most games, but in some (Smash Bros.) it
forces me to go find a keyboard/mouse and unconfigure any controllers
that I don't actually have connected. Hotplugging devices (works on macOS,
at least) + this patch remove my need to ever touch the Controller Config
dialog while in a game.
This patch makes the following changes:
- A new `BooleanSetting` in `GCPadEmu` called "Always Connected", which
defaults to false.
- `ControllerEmu` tracks whether the default device is connected on every
call to `UpdateReferences()`.
- `GCPadEmu.GetStatus()` now sets err bit to `PAD_ERR_NO_CONTROLLER` if
the default device isn't connected.
- `SIDevice_GCController` handles `PAD_ERR_NO_CONTROLLER` by imitating the
behaviour of `SIDevice_Null` (as far as I can tell, this is the only use
of the error bit from `GCPadStatus`).
I wanted to add an OSD message akin to the ones when Wiimotes get
connected/disconnected, but I haven't yet found where to put the logic.
Rather than returning 0 / not creating an expected SI interrupt. You can
test this by running VBA-M in a debugger and stopping it while it's
connected to Dolphin: on current master, Dolphin will freeze-up until it
gets a response. With this PR, Dolphin will gracefully disconnect the device, and reconnect if it starts responding again.
This is only ever queried and not set outside of the Core.cpp, so this
should just be hidden internally and just have a function exposed that
allows querying it.
Places all of the SI code under the SerialInterface namespace instead of
only the main source file. This keeps all SI code under a common name,
as well as out of the global namespace
