// SPDX-License-Identifier: GPL-2.0 /* * offload.c - USB offload related functions * * Copyright (c) 2025, Google LLC. * * Author: Guan-Yu Lin */ #include <linux/usb.h> #include "usb.h" /** * usb_offload_get - increment the offload_usage of a USB device * @udev: the USB device to increment its offload_usage * * Incrementing the offload_usage of a usb_device indicates that offload is * enabled on this usb_device; that is, another entity is actively handling USB * transfers. This information allows the USB driver to adjust its power * management policy based on offload activity. * * Return: 0 on success. A negative error code otherwise. */int usb_offload_get(struct usb_device *udev){	int ret; 	usb_lock_device(udev);	if (udev->state == USB_STATE_NOTATTACHED) {		usb_unlock_device(udev);		return -ENODEV;	} 	if (udev->state == USB_STATE_SUSPENDED ||		   udev->offload_at_suspend) {		usb_unlock_device(udev);		return -EBUSY;	} 	/*	 * offload_usage could only be modified when the device is active, since	 * it will alter the suspend flow of the device.	 */	ret = usb_autoresume_device(udev);	if (ret < 0) {		usb_unlock_device(udev);		return ret;	} 	udev->offload_usage++;	usb_autosuspend_device(udev);	usb_unlock_device(udev); 	return ret;}EXPORT_SYMBOL_GPL(usb_offload_get); /** * usb_offload_put - drop the offload_usage of a USB device * @udev: the USB device to drop its offload_usage * * The inverse operation of usb_offload_get, which drops the offload_usage of * a USB device. This information allows the USB driver to adjust its power * management policy based on offload activity. * * Return: 0 on success. A negative error code otherwise. */int usb_offload_put(struct usb_device *udev){	int ret; 	usb_lock_device(udev);	if (udev->state == USB_STATE_NOTATTACHED) {		usb_unlock_device(udev);		return -ENODEV;	} 	if (udev->state == USB_STATE_SUSPENDED ||		   udev->offload_at_suspend) {		usb_unlock_device(udev);		return -EBUSY;	} 	/*	 * offload_usage could only be modified when the device is active, since	 * it will alter the suspend flow of the device.	 */	ret = usb_autoresume_device(udev);	if (ret < 0) {		usb_unlock_device(udev);		return ret;	} 	/* Drop the count when it wasn't 0, ignore the operation otherwise. */	if (udev->offload_usage)		udev->offload_usage--;	usb_autosuspend_device(udev);	usb_unlock_device(udev); 	return ret;}EXPORT_SYMBOL_GPL(usb_offload_put); /** * usb_offload_check - check offload activities on a USB device * @udev: the USB device to check its offload activity. * * Check if there are any offload activity on the USB device right now. This * information could be used for power management or other forms of resource * management. * * The caller must hold @udev's device lock. In addition, the caller should * ensure downstream usb devices are all either suspended or marked as * "offload_at_suspend" to ensure the correctness of the return value. * * Returns true on any offload activity, false otherwise. */bool usb_offload_check(struct usb_device *udev) __must_hold(&udev->dev->mutex){	struct usb_device *child;	bool active;	int port1; 	usb_hub_for_each_child(udev, port1, child) {		usb_lock_device(child);		active = usb_offload_check(child);		usb_unlock_device(child);		if (active)			return true;	} 	return !!udev->offload_usage;}EXPORT_SYMBOL_GPL(usb_offload_check);