fldigi - Initial work to enable PnP support for fldigi. Wrote a custom tool to map between an ALSA device and a PortAudio device.

src/et-portaudio/main.c

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+/*
+ * Author  : Gaston Gonzalez
+ * Date    : 1 October 2025
+ * Purpose : Maps an ET_AUDIO ALSA device to a PortAudio device.
+ *
+ * This utility enumerates all ALSA audio devices using PortAudio
+ * to identify a currently plugged-in ET_AUDIO device. If a matching 
+ * device is found, it generates a JSON object on STDOUT containing:
+ *
+ *  - PortAudio device name
+ *  - PortAudio device index
+ *
+ * Exit Status:
+ *   0 - ET_AUDIO device found and JSON output generated successfully
+ *   1 - ET_AUDIO device not found
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "portaudio.h"
+
+#define PROC_ALSA_PATH_FMT "/proc/asound/card%d/id"
+
+// Read the ALSA card ID from the /proc filesystem
+int get_alsa_card_id(int card, char *id_buf, size_t buf_size) {
+    char path[64];
+    snprintf(path, sizeof(path), PROC_ALSA_PATH_FMT, card);
+    FILE *f = fopen(path, "r");
+    if (!f) return -1;
+    if (!fgets(id_buf, buf_size, f)) {
+        fclose(f);
+        return -1;
+    }
+    id_buf[strcspn(id_buf, "\n")] = 0; 
+    fclose(f);
+
+    return 0;
+}
+
+int main(void) {
+    PaError err;
+    int i, numDevices;
+    const PaDeviceInfo *deviceInfo;
+    const PaHostApiInfo *hostApiInfo;
+    int found = 0;  
+
+    err = Pa_Initialize();
+    if (err != paNoError) {
+        fprintf(stderr, "PortAudio error: %s\n", Pa_GetErrorText(err));
+        return 1;
+    }
+
+    numDevices = Pa_GetDeviceCount();
+    if (numDevices < 0) {
+        fprintf(stderr, "No audio devices found");
+        Pa_Terminate();
+        return 1;
+    }
+
+    for (i = 0; i < numDevices; i++) {
+        deviceInfo = Pa_GetDeviceInfo(i);
+        hostApiInfo = Pa_GetHostApiInfo(deviceInfo->hostApi);
+
+        // Only show ALSA devices
+        if (hostApiInfo && strcmp(hostApiInfo->name, "ALSA") == 0) {
+            int card = -1, device = -1;
+
+            // Extract ALSA card and device (hw:X,Y)
+            if (sscanf(deviceInfo->name, "%*[^()](hw:%d,%d)", &card, &device) == 2) {
+                char card_id[64];
+                if (get_alsa_card_id(card, card_id, sizeof(card_id)) == 0) {
+
+                    // Only print if card ID matches ET_AUDIO
+                    if (strcmp(card_id, "ET_AUDIO") == 0) {
+                        found = 1;
+                        printf("{\n");
+                        printf("  \"device\": \"%s\",\n", deviceInfo->name);
+                        printf("  \"index\": %d\n", i);
+                        printf("}\n");
+                    }
+                }
+            }
+        }
+    }
+
+    Pa_Terminate();
+    return found ? 0 : 1;
+}