feat: ddrio-async wrapper/shim driver for async IO

Wrapper/shim library to drive another ddrio in a dedicated
IO thread. Depending on the other ddrio backend used, this
can significantly improve performance while staying
compatible to the existing ddrio API interface

This turned out to be a good solution to solve performance
problems when running MAME with ddrio-p3io that is
(currently) implemented with synchronous IO calls that are
very costly: ~12 ms for a write over the ACIO protocol, ~4 ms
for a read using an IOCTL. As this already adds up to nearly
a full frame (60 fps) regarding latency, there isn't a lot
of time left to do other stuff in a synchronous update loop.
MAME's performance was unstable and dropped all the time below
100%. The result was a choppy gameplay experience.

Combining ddrio-async with ddrio-p3io, the combined backend
is able to drive inputs/outputs at a rate of ~250hz = ~4
updates per frame. This results in an average input latency
of ~4 ms which is as good as it can get with the p3io
hardware's performance limitations that I measured (see
the 4 ms for the IOCTL mentioned above).

This is more than good enough as as update frequency of
the 573 hardware is slightly less than that (I got told
something ~180 hz?).

tl;dr: Gameplay on MAME is great, smooth frame rate, IO feels
amazing and responsive.

Module.mk

@@ -104,6 +104,7 @@ include src/main/d3d9exhook/Module.mk
 include src/main/ddrhook-util/Module.mk
 include src/main/ddrhook1/Module.mk
 include src/main/ddrhook2/Module.mk
+include src/main/ddrio-async/Module.mk
 include src/main/ddrio-p3io/Module.mk
 include src/main/ddrio-mm/Module.mk
 include src/main/ddrio-smx/Module.mk
@@ -730,6 +731,7 @@ $(zipdir)/ddr-16-x64.zip: \
 	$(V)zip -j $@ $^
 
 $(zipdir)/ddr-hwio-x86.zip: \
+		build/bin/indep-32/ddrio-async.dll \
 		build/bin/indep-32/ddrio-p3io.dll \
 		build/bin/indep-32/ddrio-mm.dll \
 		build/bin/indep-32/ddrio-smx.dll \
@@ -741,6 +743,7 @@ $(zipdir)/ddr-hwio-x86.zip: \
 	$(V)zip -j $@ $^
 
 $(zipdir)/ddr-hwio-x64.zip: \
+		build/bin/indep-64/ddrio-async.dll \
 		build/bin/indep-64/ddrio-p3io.dll \
 		build/bin/indep-64/ddrio-mm.dll \
 		build/bin/indep-64/ddrio-smx.dll \

src/main/ddrio-async/Module.mk

@@ -0,0 +1,9 @@
+dlls		+= ddrio-async
+
+ldflags_ddrio-async:= \
+
+libs_ddrio-async	:= \
+	util \
+
+src_ddrio-async	:= \
+	ddrio.c \

src/main/ddrio-async/ddrio-async.def

@@ -0,0 +1,11 @@
+LIBRARY ddrio-async
+
+EXPORTS
+    ddr_io_set_loggers
+    ddr_io_fini
+    ddr_io_init
+    ddr_io_read_pad
+    ddr_io_set_lights_extio
+    ddr_io_set_lights_p3io
+    ddr_io_set_lights_hdxs_panel
+    ddr_io_set_lights_hdxs_rgb

src/main/ddrio-async/ddrio.c

@@ -0,0 +1,268 @@
+#define LOG_MODULE "ddrio-async"
+
+#include <windows.h>
+
+#include <stdatomic.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+#include <stdio.h>
+
+#include "bemanitools/ddrio.h"
+
+#include "util/log.h"
+#include "util/thread.h"
+#include "util/time.h"
+
+typedef void (*ddr_io_set_loggers_t)(
+    log_formatter_t misc,
+    log_formatter_t info,
+    log_formatter_t warning,
+    log_formatter_t fatal);
+typedef bool (*ddr_io_init_t)(
+    thread_create_t thread_create,
+    thread_join_t thread_join,
+    thread_destroy_t thread_destroy);
+typedef uint32_t (*ddr_io_read_pad_t)(void);
+typedef void (*ddr_io_set_lights_extio_t)(uint32_t extio_lights);
+typedef void (*ddr_io_set_lights_p3io_t)(uint32_t p3io_lights);
+typedef void (*ddr_io_set_lights_hdxs_panel_t)(uint32_t hdxs_lights);
+typedef void (*ddr_io_set_lights_hdxs_rgb_t)(uint8_t idx, uint8_t r, uint8_t g, uint8_t b);
+typedef void (*ddr_io_fini_t)(void);
+
+static HMODULE _child_ddr_io_module;
+
+static ddr_io_set_loggers_t _child_ddr_io_set_loggers;
+static ddr_io_init_t _child_ddr_io_init;
+static ddr_io_read_pad_t _child_ddr_io_read_pad;
+static ddr_io_set_lights_extio_t _child_ddr_io_set_lights_extio;
+static ddr_io_set_lights_p3io_t _child_ddr_io_set_lights_p3io;
+static ddr_io_set_lights_hdxs_panel_t _child_ddr_io_set_lights_hdxs_panel;
+static ddr_io_set_lights_hdxs_rgb_t _child_ddr_io_set_lights_hdxs_rgb;
+static ddr_io_fini_t _child_ddr_io_fini;
+
+static log_formatter_t _log_formatter_misc;
+static log_formatter_t _log_formatter_info;
+static log_formatter_t _log_formatter_warning;
+static log_formatter_t _log_formatter_fatal;
+
+static _Atomic(bool) _io_thread_proc_loop;
+static _Atomic(bool) _io_thread_proc_running;
+
+static _Atomic(uint32_t) _child_ddr_io_data_pad;
+static _Atomic(uint32_t) _child_ddr_io_data_extio_lights;
+static _Atomic(uint32_t) _child_ddr_io_data_p3io_lights;
+
+static int _io_thread_proc(void *ctx)
+{
+    uint64_t time_start;
+    uint64_t time_end;
+    uint64_t loop_counter;
+    uint64_t total_time;
+
+    uint32_t prev_child_ddr_io_data_extio_lights;
+    uint32_t prev_child_ddr_io_data_p3io_lights;
+
+    uint32_t local_tmp;
+
+    atomic_store_explicit(
+            &_io_thread_proc_running,
+            true,
+            memory_order_seq_cst);
+
+    log_info("IO thread running");
+
+    prev_child_ddr_io_data_extio_lights = atomic_load_explicit(
+        &_child_ddr_io_data_extio_lights, memory_order_seq_cst);
+    prev_child_ddr_io_data_p3io_lights = atomic_load_explicit(
+        &_child_ddr_io_data_p3io_lights, memory_order_seq_cst);
+
+    time_start = time_get_counter();
+    loop_counter = 0;
+
+    while (atomic_load_explicit(&_io_thread_proc_loop, memory_order_seq_cst)) {
+        local_tmp = _child_ddr_io_read_pad();
+
+        atomic_store_explicit(
+            &_child_ddr_io_data_pad,
+            local_tmp,
+            memory_order_relaxed);
+
+        // Only update outputs when they change gives this loop a major performance boost
+        // The write calls on a p3io for the outputs are very expensive (~12 ms) as they
+        // are executed over the ACIO protocol compared to only the input read
+        // calls (~4 ms) which have a dedicated IOCTL call/endpoint
+
+        local_tmp = atomic_load_explicit(
+            &_child_ddr_io_data_extio_lights,
+            memory_order_relaxed);
+
+        if (local_tmp != prev_child_ddr_io_data_extio_lights) {
+            _child_ddr_io_set_lights_extio(local_tmp);
+            prev_child_ddr_io_data_extio_lights = local_tmp;
+        }
+
+        local_tmp = atomic_load_explicit(
+            &_child_ddr_io_data_p3io_lights,
+            memory_order_relaxed);
+        
+        if (local_tmp != prev_child_ddr_io_data_p3io_lights) {
+            _child_ddr_io_set_lights_p3io(local_tmp);
+            prev_child_ddr_io_data_p3io_lights = local_tmp;
+        }
+
+        // Don't hog the CPU
+        SwitchToThread();
+
+        loop_counter++;
+    }
+
+    time_end = time_get_counter();
+    total_time = time_get_elapsed_us(time_end - time_start);
+
+    log_info("IO thread performance: total iterations %lld, avg. loop cycle time %f us",
+        loop_counter, ((double) total_time) / loop_counter);
+
+    atomic_store_explicit(
+            &_io_thread_proc_running,
+            false,
+            memory_order_seq_cst);
+
+    log_info("IO thread shut down");
+
+    return 0;
+}
+
+static void* _load_function(HMODULE module, const char* name)
+{
+    void* ptr;
+
+    ptr = GetProcAddress(module, name);
+
+    if (ptr == NULL) {
+        log_fatal("Could not find function %s in ddr3io child library", name);
+    }
+
+    return ptr;
+}
+
+void ddr_io_set_loggers(
+    log_formatter_t misc,
+    log_formatter_t info,
+    log_formatter_t warning,
+    log_formatter_t fatal)
+{
+    _log_formatter_misc = misc;
+    _log_formatter_info = info;
+    _log_formatter_warning = warning;
+    _log_formatter_fatal = fatal;
+
+    log_to_external(misc, info, warning, fatal);
+}
+
+bool ddr_io_init(
+    thread_create_t thread_create,
+    thread_join_t thread_join,
+    thread_destroy_t thread_destroy)
+{
+    log_info("Loading ddrio-async-child.dll as child ddrio library...");
+
+    _child_ddr_io_module = LoadLibraryA("ddrio-async-child.dll");
+
+    if (_child_ddr_io_module == NULL) {
+        log_warning("Loading ddrio-async-child.dll failed");
+        return false;
+    }
+
+    _child_ddr_io_set_loggers = _load_function(_child_ddr_io_module, "ddr_io_set_loggers");
+    _child_ddr_io_init = _load_function(_child_ddr_io_module, "ddr_io_init");
+    _child_ddr_io_read_pad = _load_function(_child_ddr_io_module, "ddr_io_read_pad");
+    _child_ddr_io_set_lights_extio = _load_function(_child_ddr_io_module, "ddr_io_set_lights_extio");
+    _child_ddr_io_set_lights_p3io = _load_function(_child_ddr_io_module, "ddr_io_set_lights_p3io");
+    _child_ddr_io_set_lights_hdxs_panel = _load_function(_child_ddr_io_module, "ddr_io_set_lights_hdxs_panel");
+    _child_ddr_io_set_lights_hdxs_rgb = _load_function(_child_ddr_io_module, "ddr_io_set_lights_hdxs_rgb");
+    _child_ddr_io_fini = _load_function(_child_ddr_io_module, "ddr_io_fini");
+
+    _child_ddr_io_set_loggers(
+        _log_formatter_misc,
+        _log_formatter_info,
+        _log_formatter_warning,
+        _log_formatter_fatal);
+
+    log_info("Calling child ddr_io_init...");
+
+    if (!_child_ddr_io_init(thread_create, thread_join, thread_destroy)) {
+        log_warning("Child ddr_io_init failed");
+        FreeLibrary(_child_ddr_io_module);
+
+        return false;
+    }
+
+    atomic_store_explicit(
+            &_io_thread_proc_loop,
+            true,
+            memory_order_seq_cst);
+
+    if (!thread_create(_io_thread_proc, NULL, 16384, 0)) {
+        log_warning("Creating IO thread failed");
+
+        _child_ddr_io_fini();
+        FreeLibrary(_child_ddr_io_module);
+
+        return false;
+    }
+
+    return true;
+}
+
+uint32_t ddr_io_read_pad(void)
+{
+    return atomic_load_explicit(&_child_ddr_io_data_pad, memory_order_relaxed);
+}
+
+void ddr_io_set_lights_extio(uint32_t extio_lights)
+{
+    atomic_store_explicit(
+            &_child_ddr_io_data_extio_lights,
+            extio_lights,
+            memory_order_relaxed);
+}
+
+void ddr_io_set_lights_p3io(uint32_t p3io_lights)
+{
+    atomic_store_explicit(
+            &_child_ddr_io_data_p3io_lights,
+            p3io_lights,
+            memory_order_relaxed);
+}
+
+void ddr_io_set_lights_hdxs_panel(uint32_t lights)
+{
+    // Not implemented for now
+}
+
+void ddr_io_set_lights_hdxs_rgb(uint8_t idx, uint8_t r, uint8_t g, uint8_t b)
+{
+    // Not implemented for now
+}
+
+void ddr_io_fini(void)
+{
+    atomic_store_explicit(
+            &_io_thread_proc_loop,
+            false,
+            memory_order_seq_cst);
+
+    log_info("Shutting down IO thread and waiting for it to finish...");
+
+    while (atomic_load_explicit(&_io_thread_proc_running, memory_order_seq_cst)) {
+        Sleep(1);
+    }
+
+    log_info("IO thread finished");
+
+    _child_ddr_io_fini();
+
+    FreeLibrary(_child_ddr_io_module);
+}