[usb_host] Implement disable_loop/enable_loop pattern for USB components (#14163)

esphome/components/usb_host/usb_host.h

@@ -73,12 +73,12 @@ static constexpr UBaseType_t USB_TASK_PRIORITY = 5;  // Higher priority than mai
 
 // used to report a transfer status
 struct TransferStatus {
-  bool success;
-  uint16_t error_code;
   uint8_t *data;
   size_t data_len;
-  uint8_t endpoint;
   void *user_data;
+  uint16_t error_code;
+  uint8_t endpoint;
+  bool success;
 };
 
 using transfer_cb_t = std::function<void(const TransferStatus &)>;
@@ -127,7 +127,7 @@ class USBClient : public Component {
   friend class USBHost;
 
  public:
-  USBClient(uint16_t vid, uint16_t pid) : vid_(vid), pid_(pid), trq_in_use_(0) {}
+  USBClient(uint16_t vid, uint16_t pid) : trq_in_use_(0), vid_(vid), pid_(pid) {}
   void setup() override;
   void loop() override;
   // setup must happen after the host bus has been setup
@@ -148,6 +148,10 @@ class USBClient : public Component {
   EventPool<UsbEvent, USB_EVENT_QUEUE_SIZE> event_pool;
 
  protected:
+  // Process USB events from the queue. Returns true if any work was done.
+  // Subclasses should call this instead of USBClient::loop() to combine
+  // with their own work check for a single disable_loop() decision.
+  bool process_usb_events_();
   void handle_open_state_();
   TransferRequest *get_trq_();  // Lock-free allocation using atomic bitmask (multi-consumer safe)
   virtual void disconnect();
@@ -161,20 +165,19 @@ class USBClient : public Component {
   static void usb_task_fn(void *arg);
   [[noreturn]] void usb_task_loop() const;
 
+  // Members ordered to minimize struct padding on 32-bit platforms
+  TransferRequest requests_[MAX_REQUESTS]{};
   TaskHandle_t usb_task_handle_{nullptr};
-
   usb_host_client_handle_t handle_{};
   usb_device_handle_t device_handle_{};
   int device_addr_{-1};
   int state_{USB_CLIENT_INIT};
-  uint16_t vid_{};
-  uint16_t pid_{};
   // Lock-free pool management using atomic bitmask (no dynamic allocation)
   // Bit i = 1: requests_[i] is in use, Bit i = 0: requests_[i] is available
   // Supports multiple concurrent consumers and producers (both threads can allocate/deallocate)
-  // Bitmask type automatically selected: uint16_t for <= 16 slots, uint32_t for 17-32 slots
   std::atomic<trq_bitmask_t> trq_in_use_;
-  TransferRequest requests_[MAX_REQUESTS]{};
+  uint16_t vid_{};
+  uint16_t pid_{};
 };
 class USBHost : public Component {
  public:

esphome/components/usb_host/usb_host_client.cpp

@@ -197,6 +197,9 @@ static void client_event_cb(const usb_host_client_event_msg_t *event_msg, void *
   // Push to lock-free queue (always succeeds since pool size == queue size)
   client->event_queue.push(event);
 
+  // Re-enable component loop to process the queued event
+  client->enable_loop_soon_any_context();
+
   // Wake main loop immediately to process USB event instead of waiting for select() timeout
 #if defined(USE_SOCKET_SELECT_SUPPORT) && defined(USE_WAKE_LOOP_THREADSAFE)
   App.wake_loop_threadsafe();
@@ -243,10 +246,13 @@ void USBClient::usb_task_loop() const {
   }
 }
 
-void USBClient::loop() {
+bool USBClient::process_usb_events_() {
+  bool had_work = false;
+
   // Process any events from the USB task
   UsbEvent *event;
   while ((event = this->event_queue.pop()) != nullptr) {
+    had_work = true;
     switch (event->type) {
       case EVENT_DEVICE_NEW:
         this->on_opened(event->data.device_new.address);
@@ -266,8 +272,17 @@ void USBClient::loop() {
   }
 
   if (this->state_ == USB_CLIENT_OPEN) {
+    had_work = true;
     this->handle_open_state_();
   }
+
+  return had_work;
+}
+
+void USBClient::loop() {
+  if (!this->process_usb_events_()) {
+    this->disable_loop();
+  }
 }
 
 void USBClient::handle_open_state_() {

esphome/components/usb_uart/usb_uart.cpp

@@ -172,11 +172,12 @@ bool USBUartChannel::read_array(uint8_t *data, size_t len) {
 }
 void USBUartComponent::setup() { USBClient::setup(); }
 void USBUartComponent::loop() {
-  USBClient::loop();
+  bool had_work = this->process_usb_events_();
 
   // Process USB data from the lock-free queue
   UsbDataChunk *chunk;
   while ((chunk = this->usb_data_queue_.pop()) != nullptr) {
+    had_work = true;
     auto *channel = chunk->channel;
 
 #ifdef USE_UART_DEBUGGER
@@ -198,6 +199,11 @@ void USBUartComponent::loop() {
   if (dropped > 0) {
     ESP_LOGW(TAG, "Dropped %u USB data chunks due to buffer overflow", dropped);
   }
+
+  // Disable loop when idle. Callbacks re-enable via enable_loop_soon_any_context().
+  if (!had_work) {
+    this->disable_loop();
+  }
 }
 void USBUartComponent::dump_config() {
   USBClient::dump_config();
@@ -264,6 +270,9 @@ void USBUartComponent::start_input(USBUartChannel *channel) {
       // Push always succeeds because pool size == queue size
       this->usb_data_queue_.push(chunk);
 
+      // Re-enable component loop to process the queued data
+      this->enable_loop_soon_any_context();
+
       // Wake main loop immediately to process USB data instead of waiting for select() timeout
 #if defined(USE_SOCKET_SELECT_SUPPORT) && defined(USE_WAKE_LOOP_THREADSAFE)
       App.wake_loop_threadsafe();