fix(audio): stop postNetwork waiting 15s on boards with no audio hardware

Two stacked boot-time waits fired on a board with no audio at all:

- AudioOutput gets canonicalized to the synthetic snd-dummy card's ID
  ("Dummy") when no real card exists, and the next boot then waited the
  full 10 seconds for a card named Dummy to register -- which can never
  happen, because snd-dummy is only modprobed after that wait. Treat
  "Dummy" as an explicit selection: load snd-dummy immediately so every
  wait is already satisfied, and skip the hardware-bind wait since the
  user asked for no real audio.

- deviceTreeDeclaresSoundCard() only checked that a sound node exists.
  Some device trees (e.g. AM62x boards) ship the simple-audio-card node
  with status "disabled" until an audio cape overlay enables it; a
  disabled node can never bind, so it burned the 5-second bind wait on
  every capeless board. Honor the status property (absent means enabled
  per the DT spec).

Also keep the preloaded Dummy card out of the noRealSoundcard
computation so the PipeWire skip-probe fast paths still fire, and skip
the later "No Soundcard Detected" modprobe when Dummy is already
registered. Verified on a capeless PocketBeagle2: the postNetwork audio
path drops from ~15s to ~1s, and a board with real cape audio (DT
status "okay") still gets the bind wait.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: dkulp

src/boot/FPPINIT_Audio.cpp

@@ -145,7 +145,13 @@ static bool deviceTreeDeclaresSoundCard() {
         std::string name = ep->d_name;
         // the node is "sound" or, when addressed, "sound@<unit>"
         if (name == "sound" || name.starts_with("sound@")) {
-            found = true;
+            // Some boards ship the node with status "disabled" (an audio cape
+            // overlay flips it to "okay"). A disabled node can never bind, so
+            // it must not count as "audio is expected". No status property
+            // means enabled per the DT spec.
+            std::string status = GetFileContents("/proc/device-tree/" + name + "/status");
+            TrimWhiteSpace(status);
+            found = status.empty() || status.starts_with("ok");
         }
     }
     closedir(dp);
@@ -1108,6 +1114,15 @@ static void runAudioSetup(bool recoveryPass) {
     TrimWhiteSpace(audioOutputId);
     bool legacyNumeric = !audioOutputId.empty() && audioOutputId.find_first_not_of("0123456789") == std::string::npos;
 
+    // "Dummy" selects the synthetic snd-dummy card (a box that wants no real
+    // audio). It only ever registers because we modprobe it, so waiting for it
+    // below could never succeed -- load it now and every wait in this function
+    // is already satisfied.
+    if (audioOutputId == "Dummy" && getAlsaCardNumForId("Dummy") < 0) {
+        printf("FPP - Audio device 'Dummy' selected; loading snd-dummy\n");
+        modprobe("snd-dummy");
+    }
+
     // A card selected by ID may not have registered yet: cape modules are
     // modprobed back at cape detect, but an ASoC card (e.g. the K32Max's
     // CapeAudio-pcm5102a) binds asynchronously and can land after we get here.
@@ -1164,7 +1179,10 @@ static void runAudioSetup(bool recoveryPass) {
                 v = v.substr(0, idx);
                 cards[k] = v;
                 cardLines[k] = l;
-                hasNonHDMI |= !lineHasHDMI(l);
+                // The synthetic snd-dummy is not real hardware; with an explicit
+                // "Dummy" selection it is loaded before this probe runs and must
+                // not defeat the no-real-soundcard fast paths below.
+                hasNonHDMI |= !lineHasHDMI(l) && v != "Dummy";
             }
         }
     };
@@ -1201,7 +1219,9 @@ static void runAudioSetup(bool recoveryPass) {
     // already satisfied -- it only pays out when the driver is still being
     // autoloaded. Gated so a board with neither (a BeagleBone with no audio cape,
     // the common case) waits zero.
-    if (noRealSoundcard && countRealAlsaCards() == 0 && (deviceTreeDeclaresSoundCard() || usbAudioDevicePresent())) {
+    // An explicit "Dummy" selection also skips this: the user asked for no real
+    // audio, so there is nothing worth waiting on even if hardware is present.
+    if (noRealSoundcard && audioOutputId != "Dummy" && countRealAlsaCards() == 0 && (deviceTreeDeclaresSoundCard() || usbAudioDevicePresent())) {
         printf("FPP - No soundcard yet, but audio hardware is present; waiting...\n");
         // Don't just wait on udev -- it may not have autoloaded the CPU DAI or
         // machine driver yet, and without them the card can never bind no matter
@@ -1225,7 +1245,7 @@ static void runAudioSetup(bool recoveryPass) {
             printf("FPP - No soundcard appeared after %d seconds\n", waited / 10);
         }
     }
-    if (noRealSoundcard) {
+    if (noRealSoundcard && getAlsaCardNumForId("Dummy") < 0) {
         printf("FPP - No Soundcard Detected, loading snd-dummy\n");
         modprobe("snd-dummy");
     }