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  */
  45 extern 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  */
  55 extern 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  */
  63 extern const char *usb_state_string(enum usb_device_state state);
  64
  65 #endif /* __LINUX_USB_CH9_H */