[usb_uart] Wake main loop immediately when USB data arrives (#12148)

esphome/components/usb_uart/__init__.py

@@ -1,4 +1,5 @@
 import esphome.codegen as cg
+from esphome.components import socket
 from esphome.components.uart import (
     CONF_DATA_BITS,
     CONF_PARITY,
@@ -17,7 +18,7 @@ from esphome.const import (
 )
 from esphome.cpp_types import Component
 
-AUTO_LOAD = ["uart", "usb_host", "bytebuffer"]
+AUTO_LOAD = ["uart", "usb_host", "bytebuffer", "socket"]
 CODEOWNERS = ["@clydebarrow"]
 
 usb_uart_ns = cg.esphome_ns.namespace("usb_uart")
@@ -116,6 +117,10 @@ CONFIG_SCHEMA = cv.ensure_list(
 
 
 async def to_code(config):
+    # Enable wake_loop_threadsafe for low-latency USB data processing
+    # The USB task queues data events that need immediate processing
+    socket.require_wake_loop_threadsafe()
+
     for device in config:
         var = await register_usb_client(device)
         for index, channel in enumerate(device[CONF_CHANNELS]):

esphome/components/usb_uart/usb_uart.cpp

@@ -2,6 +2,7 @@
 #if defined(USE_ESP32_VARIANT_ESP32S2) || defined(USE_ESP32_VARIANT_ESP32S3) || defined(USE_ESP32_VARIANT_ESP32P4)
 #include "usb_uart.h"
 #include "esphome/core/log.h"
+#include "esphome/core/application.h"
 #include "esphome/components/uart/uart_debugger.h"
 
 #include <cinttypes>
@@ -262,6 +263,11 @@ void USBUartComponent::start_input(USBUartChannel *channel) {
       // Push to lock-free queue for main loop processing
       // Push always succeeds because pool size == queue size
       this->usb_data_queue_.push(chunk);
+
+      // 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();
+#endif
     }
 
     // On success, restart input immediately from USB task for performance