media: avoid bulk clamp on non-bulk uvc kernels

Cargo.lock

@@ -1652,7 +1652,7 @@ checksum = "09edd9e8b54e49e587e4f6295a7d29c3ea94d469cb40ab8ca70b288248a81db2"
 
 [[package]]
 name = "lesavka_client"
-version = "0.22.31"
+version = "0.22.32"
 dependencies = [
  "anyhow",
  "async-stream",
@@ -1686,7 +1686,7 @@ dependencies = [
 
 [[package]]
 name = "lesavka_common"
-version = "0.22.31"
+version = "0.22.32"
 dependencies = [
  "anyhow",
  "base64",
@@ -1698,7 +1698,7 @@ dependencies = [
 
 [[package]]
 name = "lesavka_server"
-version = "0.22.31"
+version = "0.22.32"
 dependencies = [
  "anyhow",
  "base64",

client/Cargo.toml

@@ -4,7 +4,7 @@ path                    = "src/main.rs"
 
 [package]
 name                    = "lesavka_client"
-version                 = "0.22.31"
+version                 = "0.22.32"
 edition                 = "2024"
 
 [dependencies]

common/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name                    = "lesavka_common"
-version = "0.22.31"
+version = "0.22.32"
 edition                 = "2024"
 build                   = "build.rs"
 

docs/operational-env.md

@@ -313,7 +313,7 @@ from `LESAVKA_CLIENT_PKI_SSH_SOURCE` over SSH. Runtime clients require the insta
 | `LESAVKA_UVC_APP_MAX_BYTES` | server UVC appsrc memory guard; defaults to `4194304` queued bytes |
 | `LESAVKA_UVC_APP_MAX_TIME_NS` | server UVC appsrc memory guard; defaults to `200000000` ns of queued media |
 | `LESAVKA_UVC_BLOCKING` | server hardware/device override |
-| `LESAVKA_UVC_BULK` | UVC transfer-mode override; defaults to `1` so patched kernels prefer reliable bulk transfer over lossy isochronous MJPEG. Set `0` to force classic isochronous descriptors |
+| `LESAVKA_UVC_BULK` | UVC transfer-mode override; defaults to `1` so patched kernels prefer reliable bulk transfer over lossy isochronous MJPEG. If the live kernel does not expose `streaming_bulk`, Lesavka falls back to isochronous descriptors without the 512-byte bulk clamp. Set `0` to force classic isochronous descriptors |
 | `LESAVKA_UVC_BUFFER_COUNT` | UVC helper freshness override; number of queued gadget output buffers, defaults to `2` for live-call freshness |
 | `LESAVKA_UVC_BY_PATH_ROOT` | server hardware/device override |
 | `LESAVKA_UVC_CODEC` | server hardware/device override |

scripts/daemon/lesavka-core.sh

@@ -181,8 +181,10 @@ flag_enabled() {
     esac
 }
 if flag_enabled "${LESAVKA_UVC_BULK:-1}"; then
+    UVC_BULK_REQUESTED=1
     UVC_BULK=1
 else
+    UVC_BULK_REQUESTED=
     UVC_BULK=
 fi
 UVC_CODEC=${LESAVKA_UVC_CODEC:-mjpeg}
@@ -294,18 +296,20 @@ compute_uvc_payload_cap() {
     UVC_PAYLOAD_CAP=$((bytes * pct / 100))
 }
 
-compute_uvc_payload_cap
+apply_uvc_payload_limits() {
-if [[ -n $UVC_PAYLOAD_CAP && $UVC_PAYLOAD_CAP -gt 0 ]]; then
+    compute_uvc_payload_cap
-    log "UVC fifo periodic=${UVC_FIFO_PERIODIC:-?} np=${UVC_FIFO_NP:-?} cap=${UVC_PAYLOAD_CAP}B pct=${UVC_PAYLOAD_PCT:-?} src=${UVC_PAYLOAD_SRC:-?} udc=${UVC_UDC:-?}"
+    if [[ -n $UVC_PAYLOAD_CAP && $UVC_PAYLOAD_CAP -gt 0 ]]; then
-    if ((UVC_MAXPACKET > UVC_PAYLOAD_CAP)); then
+        log "UVC fifo periodic=${UVC_FIFO_PERIODIC:-?} np=${UVC_FIFO_NP:-?} cap=${UVC_PAYLOAD_CAP}B pct=${UVC_PAYLOAD_PCT:-?} src=${UVC_PAYLOAD_SRC:-?} udc=${UVC_UDC:-?}"
-        log "clamping UVC maxpacket $UVC_MAXPACKET -> $UVC_PAYLOAD_CAP"
+        if ((UVC_MAXPACKET > UVC_PAYLOAD_CAP)); then
-        UVC_MAXPACKET=$UVC_PAYLOAD_CAP
+            log "clamping UVC maxpacket $UVC_MAXPACKET -> $UVC_PAYLOAD_CAP"
+            UVC_MAXPACKET=$UVC_PAYLOAD_CAP
+        fi
     fi
-fi
+    if [[ -n $UVC_BULK && $UVC_MAXPACKET -gt 512 ]]; then
-if [[ -n $UVC_BULK && $UVC_MAXPACKET -gt 512 ]]; then
+        log "clamping UVC maxpacket $UVC_MAXPACKET -> 512 (bulk)"
-    log "clamping UVC maxpacket $UVC_MAXPACKET -> 512 (bulk)"
+        UVC_MAXPACKET=512
-    UVC_MAXPACKET=512
+    fi
-fi
+}
 if [[ -n ${LESAVKA_UVC_MJPEG:-} ]]; then
     UVC_CODEC=mjpeg
 fi
@@ -588,6 +592,19 @@ if [[ -z $DISABLE_UVC ]]; then
   # ----------------------- UVC function (usb‑video) ------------------
   mkdir -p "$G/functions/uvc.usb0"
   F="$G/functions/uvc.usb0"
+  if [[ -n $UVC_BULK_REQUESTED ]]; then
+    if [[ -e "$F/streaming_bulk" ]]; then
+      UVC_BULK=1
+    else
+      # Some kernels do not expose the patched bulk-transfer knob. Falling
+      # back to isochronous must also avoid the 512-byte bulk packet clamp;
+      # otherwise MJPEG frames are much more likely to arrive truncated.
+      log "UVC bulk requested but this kernel lacks streaming_bulk; using isochronous descriptors"
+      UVC_BULK=
+      UVC_MAXPACKET=${LESAVKA_UVC_MAXPACKET:-1024}
+    fi
+  fi
+  apply_uvc_payload_limits
   echo "$UVC_STREAMING_INTERVAL" >"$F/streaming_interval"
   echo "$UVC_MAXPACKET" >"$F/streaming_maxpacket"
   echo "$UVC_MAXBURST" >"$F/streaming_maxburst"

server/Cargo.toml

@@ -10,7 +10,7 @@ bench                   = false
 
 [package]
 name                    = "lesavka_server"
-version                 = "0.22.31"
+version                 = "0.22.32"
 edition                 = "2024"
 autobins                = false
 

server/src/bin/lesavka-uvc.real.inc

@@ -669,7 +669,17 @@ fn uvc_frame_size_guard_enabled() -> bool {
 }
 
 fn uvc_bulk_transfer_enabled() -> bool {
-    env_flag_enabled("LESAVKA_UVC_BULK", true)
+    if !env_flag_enabled("LESAVKA_UVC_BULK", true) {
+        return false;
+    }
+    let base = std::path::Path::new(CONFIGFS_UVC_BASE);
+    if base.exists() && !base.join("streaming_bulk").exists() {
+        eprintln!(
+            "[lesavka-uvc] UVC bulk requested but live configfs has no streaming_bulk; using isochronous payload sizing"
+        );
+        return false;
+    }
+    true
 }
 
 fn uvc_frame_size_for_active_mode(width: u32, height: u32, fps: u32) -> u32 {

server/src/bin/lesavka_uvc/coverage_model.rs

@@ -19,6 +19,8 @@ const UVC_DATA_SIZE: usize = 60;
 const UVC_STRING_CONTROL_IDX: u8 = 0;
 #[cfg(coverage)]
 const UVC_STRING_STREAMING_IDX: u8 = 1;
+#[cfg(coverage)]
+const CONFIGFS_UVC_BASE: &str = "/sys/kernel/config/usb_gadget/lesavka/functions/uvc.usb0";
 
 #[cfg(coverage)]
 const USB_DIR_IN: u8 = 0x80;

server/src/bin/lesavka_uvc/coverage_startup.rs

@@ -222,7 +222,14 @@ fn uvc_frame_size_guard_enabled() -> bool {
 
 #[cfg(coverage)]
 fn uvc_bulk_transfer_enabled() -> bool {
-    env_flag_enabled("LESAVKA_UVC_BULK", true)
+    if !env_flag_enabled("LESAVKA_UVC_BULK", true) {
+        return false;
+    }
+    let base = std::path::Path::new(CONFIGFS_UVC_BASE);
+    if base.exists() && !base.join("streaming_bulk").exists() {
+        return false;
+    }
+    true
 }
 
 #[cfg(coverage)]

tests/contract/scripts/daemon/server_core_script_contract.rs

@@ -97,6 +97,9 @@ fn core_script_keeps_uvc_output_on_supported_mjpeg_descriptor() {
         "UVC codec '$UVC_CODEC' is not supported by the MJPEG UVC helper; using mjpeg",
         "UVC_CODEC=mjpeg",
         "flag_enabled \"${LESAVKA_UVC_BULK:-1}\"",
+        "UVC bulk requested but this kernel lacks streaming_bulk; using isochronous descriptors",
+        "apply_uvc_payload_limits",
+        "UVC_MAXPACKET=${LESAVKA_UVC_MAXPACKET:-1024}",
         "uvc_mjpeg_frame_size_for_fps()",
         "UVC_MJPEG_BUDGET_BYTES_PER_SEC=${LESAVKA_UVC_MJPEG_BUDGET_BYTES_PER_SEC:-10000000}",
         "UVC_FRAME_SIZE=\"$(uvc_mjpeg_frame_size_for_fps \"$UVC_FPS\")\"",

tests/contract/server/uvc/server_uvc_binary_contract.rs

@@ -341,6 +341,14 @@ mod uvc_binary {
         });
     }
 
+    #[test]
+    fn uvc_bulk_mode_is_tied_to_live_configfs_support() {
+        let source = include_str!("../../../../server/src/bin/lesavka-uvc.real.inc");
+
+        assert!(source.contains("base.exists() && !base.join(\"streaming_bulk\").exists()"));
+        assert!(source.contains("using isochronous payload sizing"));
+    }
+
     #[test]
     #[serial]
     fn uvc_stats_snapshot_can_be_disabled_or_written() {