[feat](trx-backend-soapysdr): add hardware AGC toggle and SDR settings UI row

Add hardware AGC on/off control for SoapySDR backend, wired through the
full stack from RigCommand to the web UI:

- RigCommand::SetSdrAgc(bool) + ClientCommand::SetSdrAgc in protocol
- set_sdr_agc() on RigCat trait (not-supported default)
- SoapySdrRig: agc_enabled field, set_sdr_agc() via pipeline agc_cmd,
  sdr_agc_enabled in filter_state(); removes the "not yet implemented"
  warning — gain_mode="auto" now properly enables hardware AGC via
  SoapySDR set_gain_mode()
- IqSource::set_gain_mode() trait method; RealIqSource implements it
- SdrPipeline: agc_cmd channel, read loop applies it each iteration
- POST /set_sdr_agc endpoint in trx-frontend-http
- New "SDR settings" full-row in index.html with Hardware AGC checkbox
  and RF Gain (moved out of WFM controls); row hidden when
  show_sdr_gain_control is false
- app.js: AGC checkbox handler, disables RF gain input while AGC is on,
  syncs checkbox state from filter.sdr_agc_enabled

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Signed-off-by: Stan Grams <sjg@haxx.space>

src/trx-server/src/rig_task.rs

@@ -563,6 +563,14 @@ async fn process_command(
             let _ = ctx.state_tx.send(ctx.state.clone());
             return snapshot_from(ctx.state);
         }
+        RigCommand::SetSdrAgc(enabled) => {
+            if let Err(e) = ctx.rig.set_sdr_agc(enabled).await {
+                return Err(RigError::communication(format!("set_sdr_agc: {e}")));
+            }
+            ctx.state.filter = ctx.rig.filter_state();
+            let _ = ctx.state_tx.send(ctx.state.clone());
+            return snapshot_from(ctx.state);
+        }
         RigCommand::SetSdrSquelch {
             enabled,
             threshold_db,

src/trx-server/trx-backend/trx-backend-soapysdr/src/dsp.rs

@@ -57,6 +57,12 @@ pub trait IqSource: Send + 'static {
         Ok(())
     }
 
+    /// Enable or disable hardware automatic gain control.  Default
+    /// implementation is a no-op for sources that do not support AGC.
+    fn set_gain_mode(&mut self, _automatic: bool) -> Result<(), String> {
+        Ok(())
+    }
+
     /// Gives a source-specific implementation a chance to recover from a
     /// read error (for example, by rearming a hardware stream after overflow).
     /// Returns `true` when an active recovery action was attempted.
@@ -100,6 +106,9 @@ pub struct SdrPipeline {
     /// Write `Some(gain_db)` here to adjust the hardware RX gain.
     /// The IQ read loop picks it up on the next iteration.
     pub gain_cmd: Arc<std::sync::Mutex<Option<f64>>>,
+    /// Write `Some(enabled)` here to switch hardware AGC on or off.
+    /// The IQ read loop picks it up on the next iteration.
+    pub agc_cmd: Arc<std::sync::Mutex<Option<bool>>>,
     /// Current hardware center frequency in Hz, kept in sync by `SoapySdrRig`.
     /// Read by `SdrVirtualChannelManager` to validate and compute IF offsets.
     pub shared_center_hz: Arc<AtomicI64>,
@@ -174,6 +183,8 @@ impl SdrPipeline {
         let thread_retune_cmd = retune_cmd.clone();
         let gain_cmd: Arc<std::sync::Mutex<Option<f64>>> = Arc::new(std::sync::Mutex::new(None));
         let thread_gain_cmd = gain_cmd.clone();
+        let agc_cmd: Arc<std::sync::Mutex<Option<bool>>> = Arc::new(std::sync::Mutex::new(None));
+        let thread_agc_cmd = agc_cmd.clone();
 
         std::thread::Builder::new()
             .name("sdr-iq-read".to_string())
@@ -186,6 +197,7 @@ impl SdrPipeline {
                     thread_spectrum_buf,
                     thread_retune_cmd,
                     thread_gain_cmd,
+                    thread_agc_cmd,
                 );
             })
             .expect("failed to spawn sdr-iq-read thread");
@@ -198,6 +210,7 @@ impl SdrPipeline {
             sdr_sample_rate,
             retune_cmd,
             gain_cmd,
+            agc_cmd,
             shared_center_hz: Arc::new(AtomicI64::new(0)),
             audio_sample_rate,
             audio_channels: output_channels,
@@ -277,6 +290,7 @@ fn iq_read_loop(
     spectrum_buf: Arc<Mutex<Option<Vec<f32>>>>,
     retune_cmd: Arc<std::sync::Mutex<Option<f64>>>,
     gain_cmd: Arc<std::sync::Mutex<Option<f64>>>,
+    agc_cmd: Arc<std::sync::Mutex<Option<bool>>>,
 ) {
     let mut block = vec![Complex::new(0.0_f32, 0.0_f32); IQ_BLOCK_SIZE];
     let block_duration_ms = if sdr_sample_rate > 0 {
@@ -309,6 +323,15 @@ fn iq_read_loop(
                 }
             }
         }
+        if let Ok(mut cmd) = agc_cmd.try_lock() {
+            if let Some(enabled) = cmd.take() {
+                if let Err(e) = source.set_gain_mode(enabled) {
+                    tracing::warn!("SDR AGC mode change to {} failed: {}", enabled, e);
+                } else {
+                    tracing::info!("SDR AGC mode set to {}", enabled);
+                }
+            }
+        }
 
         let n = match source.read_into(&mut block) {
             Ok(n) => {

src/trx-server/trx-backend/trx-backend-soapysdr/src/lib.rs

@@ -52,6 +52,8 @@ pub struct SoapySdrRig {
     gain_db: f64,
     /// Optional hard ceiling for the applied hardware gain in dB.
     max_gain_db: Option<f64>,
+    /// Whether hardware AGC is currently enabled.
+    agc_enabled: bool,
     /// Whether software squelch is enabled on primary channel (except WFM mode).
     squelch_enabled: bool,
     /// Software squelch threshold (dBFS) on primary channel.
@@ -133,13 +135,7 @@ impl SoapySdrRig {
             max_gain_db,
         );
 
-        if gain_mode == "auto" {
-            tracing::warn!(
-                "SoapySDR hardware AGC is not yet implemented; falling back to configured \
-                 gain of {} dB",
-                gain_db,
-            );
-        }
+        let agc_enabled = gain_mode == "auto";
 
         let effective_gain_db = max_gain_db
             .map(|max_gain| gain_db.min(max_gain))
@@ -289,6 +285,7 @@ impl SoapySdrRig {
             wfm_denoise: WfmDenoiseLevel::Auto,
             gain_db,
             max_gain_db,
+            agc_enabled,
             squelch_enabled,
             squelch_threshold_db,
             ais_channel_indices: Some((primary_channel_count, primary_channel_count + 1)),
@@ -582,6 +579,19 @@ impl RigCat for SoapySdrRig {
         })
     }
 
+    fn set_sdr_agc<'a>(
+        &'a mut self,
+        enabled: bool,
+    ) -> Pin<Box<dyn std::future::Future<Output = DynResult<()>> + Send + 'a>> {
+        Box::pin(async move {
+            self.agc_enabled = enabled;
+            if let Ok(mut cmd) = self.pipeline.agc_cmd.lock() {
+                *cmd = Some(enabled);
+            }
+            Ok(())
+        })
+    }
+
     fn set_sdr_squelch<'a>(
         &'a mut self,
         enabled: bool,
@@ -793,6 +803,7 @@ impl RigCat for SoapySdrRig {
                     .map(|max_gain| self.gain_db.min(max_gain))
                     .unwrap_or(self.gain_db),
             ),
+            sdr_agc_enabled: Some(self.agc_enabled),
             sdr_squelch_enabled: Some(self.squelch_enabled),
             sdr_squelch_threshold_db: Some(self.squelch_threshold_db as f64),
             wfm_deemphasis_us: self.wfm_deemphasis_us,

src/trx-server/trx-backend/trx-backend-soapysdr/src/real_iq_source.rs

@@ -179,6 +179,12 @@ impl IqSource for RealIqSource {
             .map_err(|e| format!("Failed to set SDR gain: {}", e))
     }
 
+    fn set_gain_mode(&mut self, automatic: bool) -> Result<(), String> {
+        self.device
+            .set_gain_mode(soapysdr::Direction::Rx, 0, automatic)
+            .map_err(|e| format!("Failed to set SDR gain mode: {}", e))
+    }
+
     fn handle_read_error(&mut self, err: &str, streak: u32) -> Result<bool, String> {
         const OVERFLOW_RESTART_STREAK: u32 = 50;
         const NON_OVERFLOW_RESTART_STREAK: u32 = 10;