LXR linux/include/linux/usb/ch9.h

   1/* SPDX-License-Identifier: GPL-2.0 */
   2/*
   3 * This file holds USB constants and structures that are needed for
   4 * USB device APIs.  These are used by the USB device model, which is
   5 * defined in chapter 9 of the USB 2.0 specification and in the
   6 * Wireless USB 1.0 (spread around).  Linux has several APIs in C that
   7 * need these:
   8 *
   9 * - the master/host side Linux-USB kernel driver API;
  10 * - the "usbfs" user space API; and
  11 * - the Linux "gadget" slave/device/peripheral side driver API.
  12 *
  13 * USB 2.0 adds an additional "On The Go" (OTG) mode, which lets systems
  14 * act either as a USB master/host or as a USB slave/device.  That means
  15 * the master and slave side APIs benefit from working well together.
  16 *
  17 * There's also "Wireless USB", using low power short range radios for
  18 * peripheral interconnection but otherwise building on the USB framework.
  19 *
  20 * Note all descriptors are declared '__attribute__((packed))' so that:
  21 *
  22 * [a] they never get padded, either internally (USB spec writers
  23 *     probably handled that) or externally;
  24 *
  25 * [b] so that accessing bigger-than-a-bytes fields will never
  26 *     generate bus errors on any platform, even when the location of
  27 *     its descriptor inside a bundle isn't "naturally aligned", and
  28 *
  29 * [c] for consistency, removing all doubt even when it appears to
  30 *     someone that the two other points are non-issues for that
  31 *     particular descriptor type.
  32 */
  33#ifndef __LINUX_USB_CH9_H
  34#define __LINUX_USB_CH9_H
  35
  36#include <linux/device.h>
  37#include <uapi/linux/usb/ch9.h>
  38
  39/**
  40 * usb_speed_string() - Returns human readable-name of the speed.
  41 * @speed: The speed to return human-readable name for.  If it's not
  42 *   any of the speeds defined in usb_device_speed enum, string for
  43 *   USB_SPEED_UNKNOWN will be returned.
  44 */
  45extern const char *usb_speed_string(enum usb_device_speed speed);
  46
  47/**
  48 * usb_get_maximum_speed - Get maximum requested speed for a given USB
  49 * controller.
  50 * @dev: Pointer to the given USB controller device
  51 *
  52 * The function gets the maximum speed string from property "maximum-speed",
  53 * and returns the corresponding enum usb_device_speed.
  54 */
  55extern enum usb_device_speed usb_get_maximum_speed(struct device *dev);
  56
  57/**
  58 * usb_state_string - Returns human readable name for the state.
  59 * @state: The state to return a human-readable name for. If it's not
  60 *      any of the states devices in usb_device_state_string enum,
  61 *      the string UNKNOWN will be returned.
  62 */
  63extern const char *usb_state_string(enum usb_device_state state);
  64
  65#endif /* __LINUX_USB_CH9_H */
  66