usb: device_next: allow message callback to be executed from USBD thread

Allowing message callback execution from the USBD thread saves about 800
bytes. For small devices, the option can be useful to reduce flash/RAM
usage, those with enough resources should not bother about it.

Signed-off-by: Johann Fischer <[email protected]>

Author: jfischer-no

include/zephyr/usb/usbd.h

@@ -269,10 +269,14 @@ struct usbd_status {
 /**
  * @brief Callback type definition for USB device message delivery
  *
- * The implementation uses the system workqueue, and a callback provided and
- * registered by the application. The application callback is called in the
- * context of the system workqueue. Notification messages are stored in a queue
- * and delivered to the callback in sequence.
+ * If the Kconfig option USBD_MSG_DEFERRED_MODE is enabled, then the callback
+ * is executed in the context of the system workqueue. Notification messages are
+ * stored in a queue and delivered to the callback in sequence.
+ *
+ * If the Kconfig option USBD_MSG_DEFERRED_MODE is disabled, the callback is
+ * executed in the context of the USB device stack thread. The user should make
+ * sure that the callback execution does not block or disrupt device stack
+ * handling.
  *
  * @param[in] ctx Pointer to USB device support context
  * @param[in] msg Pointer to USB device message

subsys/usb/device_next/Kconfig

@@ -81,8 +81,15 @@ config USBD_MSG_SLAB_COUNT
 	help
 	  Maximum number of USB device notification messages that can be queued.
 
+config USBD_MSG_DEFERRED_MODE
+	bool "Execute message callback from system workqueue"
+	default y
+	help
+	  Execute message callback from system workqueue. If disabled, message
+	  callback will be executed in the device stack context.
+
 config USBD_MSG_WORK_DELAY
-	int "USB device notification messages work delay"
+	int "USB device notification messages work delay" if USBD_MSG_DEFERRED_MODE
 	range 1 100
 	default 1
 	help

subsys/usb/device_next/usbd_msg.c

@@ -116,7 +116,11 @@ void usbd_msg_pub_simple(struct usbd_context *const ctx,
 	};
 
 	if (ctx->msg_cb != NULL) {
-		usbd_msg_pub(ctx, msg);
+		if (IS_ENABLED(CONFIG_USBD_MSG_DEFERRED_MODE)) {
+			usbd_msg_pub(ctx, msg);
+		} else {
+			ctx->msg_cb(ctx, &msg);
+		}
 	}
 }
 
@@ -129,6 +133,10 @@ void usbd_msg_pub_device(struct usbd_context *const ctx,
 	};
 
 	if (ctx->msg_cb != NULL) {
-		usbd_msg_pub(ctx, msg);
+		if (IS_ENABLED(CONFIG_USBD_MSG_DEFERRED_MODE)) {
+			usbd_msg_pub(ctx, msg);
+		} else {
+			ctx->msg_cb(ctx, &msg);
+		}
 	}
 }