STM32 UDC: fix transmission on halted endpoints

drivers/usb/udc/udc_stm32.c

@@ -829,6 +829,14 @@ static int udc_stm32_ep_set_halt(const struct device *dev,
 		return -EIO;
 	}
 
+	/*
+	 * Mark non-control endpoint as halted
+	 * to indicate stall condition
+	 */
+	if (USB_EP_GET_IDX(cfg->addr) != 0) {
+		cfg->stat.halted = true;
+	}
+
 	return 0;
 }
 
@@ -847,6 +855,21 @@ static int udc_stm32_ep_clear_halt(const struct device *dev,
 		return -EIO;
 	}
 
+	/* Clear halted state to resume normal operation */
+	cfg->stat.halted = false;
+
+	/*
+	 * If endpoint is non-control, has pending data, is IN direction,
+	 * and not busy, trigger retransmission to continue data flow
+	 */
+	if (USB_EP_GET_IDX(cfg->addr)) {
+		struct net_buf *buf = udc_buf_peek(cfg);
+
+		if (buf && USB_EP_DIR_IS_IN(cfg->addr) && !udc_ep_is_busy(cfg)) {
+			udc_stm32_tx(dev, cfg, buf);
+		}
+	}
+
 	return 0;
 }
 
@@ -880,7 +903,18 @@ static int udc_stm32_ep_enqueue(const struct device *dev,
 	lock_key = irq_lock();
 
 	if (USB_EP_DIR_IS_IN(epcfg->addr)) {
-		ret = udc_stm32_tx(dev, epcfg, buf);
+		if (!epcfg->stat.halted) {
+			/* Endpoint is not halted, safe to transmit data */
+			ret = udc_stm32_tx(dev, epcfg, buf);
+		} else {
+			/*
+			 * Endpoint is halted (stalled) by the host
+			 * Skip transmission to avoid protocol violations
+			 * and potential data corruption
+			 */
+			LOG_DBG("ep 0x%02x halted", epcfg->addr);
+			ret = 0;
+		}
 	} else {
 		ret = udc_stm32_rx(dev, epcfg, buf);
 	}