Fix puck activation after firmware updates (#44)

The receiver stopped working after a controller firmware update. Original
diagnosis and fix by @danbosscher; extended here for Bluetooth, Steam
handoff, and several defects found during QA on the hardware.

The puck publishes a controller interface per slot plus a management
endpoint, and on current firmware an empty slot rejects the lizard-mode
command outright.

- Enumerate only the controller collection (FF00:0001), excluding the
  puck's management endpoint at FF00:0002
- Wait for a live 0x42/0x45 state report before sending feature commands,
  and skip slots that never produce one
- Prefer an exclusive claim but accept a shared handle when Windows keeps
  a compatible write handle open — only while Steam is absent, since a
  handle held with Steam running is probably Steam's, and driving the
  controller alongside it is worse than refusing. Refusing is what
  escalates to the device cycle that takes the handle back.
- Add the Nereid receiver PID (0x1305)

Defects found by QA and fixed here:

- The battery payload is [chargeState, percent] on every transport, not
  just Bluetooth. A 92% battery was reported, and fed to the DS4 battery
  level, as 1%.
- Game mode could not tell an idle receiver from a contested one, so a
  controller that was merely switched off triggered three device cycles,
  restarting the receiver's devnodes for nothing.
- A receiver raises no device event when a slot becomes occupied, so
  waking a controller went unnoticed for as long as it was left. Poll for
  it instead.
- Overlapping cycles undid successful claims: a cycle is asynchronous, and
  the arrivals it generated re-entered the acquire path and fired another
  on top of it, ripping the device back out a second after game mode came
  up. Cycles are now spaced.
- Failure was announced while the last cycle was still landing — the alert
  fired one second before success. The verdict now waits out a grace
  period.

Verified on the puck, Bluetooth, and wired: handoff to Steam on game
launch, reclaim afterwards, and no duplicate input.

Reclaiming takes around nine seconds on a four-slot receiver, dominated by
SetupDiCallClassInstaller tearing down each interface in turn. Three
attempts to shorten it (batching the cycle, a shorter settle, cycling only
the contested interface) all regressed the reclaim and were reverted; it
needs to be worked out against hardware rather than reasoned about.

Co-Authored-By: Dan Bosscher <danbosscher@users.noreply.github.com>
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/main.cpp

@@ -92,16 +92,51 @@ static std::vector<IfaceInfo> EnumerateAllValveDevices() {
             HidD_FreePreparsedData(preparsed);
         }
 
+        CloseHandle(h);
+
+        // Can a write-exclusive handle be had? A "no" here is exactly why game
+        // mode used to refuse a perfectly good controller, so it is worth
+        // seeing per interface instead of inferring it from a later failure.
+        HANDLE exclusive = CreateFileW(path.c_str(), GENERIC_READ | GENERIC_WRITE,
+                                       FILE_SHARE_READ, nullptr, OPEN_EXISTING,
+                                       FILE_FLAG_OVERLAPPED, nullptr);
+        const DWORD exclusiveErr =
+            exclusive == INVALID_HANDLE_VALUE ? GetLastError() : ERROR_SUCCESS;
+        if (exclusive != INVALID_HANDLE_VALUE) CloseHandle(exclusive);
+
+        // Which slot is actually live? The puck publishes four controller
+        // interfaces and only an occupied one emits state reports.
+        const bool controllerIface =
+            info.usagePage == SteamController::VENDOR_USAGE_PAGE
+            && info.usage == SteamController::CONTROLLER_USAGE;
+        size_t  reportLen = 0;
+        uint8_t reportId  = 0;
+        if (controllerIface) {
+            HidDevice probe;
+            if (probe.Open(path)) {
+                uint8_t report[64]{};
+                reportLen = probe.ReadInputReport(report, sizeof(report), 250);
+                if (reportLen > 0) reportId = report[0];
+            }
+        }
+
         const bool vendor = (info.usagePage == SteamController::VENDOR_USAGE_PAGE);
         printf("  [%zu]%s PID=%04X  Usage=%04X:%04X  In=%u Out=%u Feat=%u  fw=0x%04X  %s\n"
                "      \"%ls\"  serial=%ls\n"
-               "      path: %ls\n",
+               "      exclusive=%s",
                out.size(), vendor ? "*" : " ", attrs.ProductID,
                info.usagePage, info.usage, inLen, outLen, featLen,
                attrs.VersionNumber, GuessTransport(path),
-               productBuf, serialBuf, path.c_str());
+               productBuf, serialBuf,
+               exclusiveErr == ERROR_SUCCESS ? "yes" : "no");
+        if (exclusiveErr != ERROR_SUCCESS)
+            printf(" (error %lu)", exclusiveErr);
+        if (reportLen > 0)
+            printf("  live=0x%02X/%zu bytes", reportId, reportLen);
+        else if (controllerIface)
+            printf("  live=none (empty slot?)");
+        printf("\n      path: %ls\n", path.c_str());
 
-        CloseHandle(h);
         out.push_back(std::move(info));
     }
     printf("  (* = vendor collection 0x%04X — the game-input interface)\n\n",
@@ -178,10 +213,18 @@ static bool RunCalibration(SteamController& ctrl) {
 
     // Apply force-show overrides before marking axes.
     auto forceShow = [](size_t i) -> bool {
-        if (FORCE_SHOW_BYTES_10_11 && (i == 10 || i == 11)) return true;
-        if (FORCE_SHOW_BYTES_12_13 && (i == 12 || i == 13)) return true;
-        if (FORCE_SHOW_BYTES_14_15 && (i == 14 || i == 15)) return true;
-        if (FORCE_SHOW_BYTES_16_17 && (i == 16 || i == 17)) return true;
+        if constexpr (FORCE_SHOW_BYTES_10_11) {
+            if (i == 10 || i == 11) return true;
+        }
+        if constexpr (FORCE_SHOW_BYTES_12_13) {
+            if (i == 12 || i == 13) return true;
+        }
+        if constexpr (FORCE_SHOW_BYTES_14_15) {
+            if (i == 14 || i == 15) return true;
+        }
+        if constexpr (FORCE_SHOW_BYTES_16_17) {
+            if (i == 16 || i == 17) return true;
+        }
         return false;
     };
 
@@ -316,7 +359,10 @@ int main(int argc, char** argv) {
     signal(SIGINT,  OnSignal);
     signal(SIGTERM, OnSignal);
 
-    const bool enumOnly = (argc > 1 && strcmp(argv[1], "--enum") == 0);
+    // --enumerate-only is accepted as an alias so instructions written against
+    // the puck investigation keep working.
+    const bool enumOnly = argc > 1 && (strcmp(argv[1], "--enum") == 0
+                                    || strcmp(argv[1], "--enumerate-only") == 0);
     const bool imuMode  = (argc > 1 && strcmp(argv[1], "--imu")  == 0);
 
     printf("=== SteamProbe — 2026 Steam Controller discovery tool ===\n\n");
@@ -340,6 +386,9 @@ int main(int argc, char** argv) {
         : defaultIdx;
     printf("Opening [%zu] (%s)...\n\n", chosen, GuessTransport(ifaces[chosen].path));
 
+    if (argc > 1 && strcmp(argv[1], "--enumerate-only") == 0)
+        return 0;
+
     SteamController controller;
     g_controller = &controller;