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Linux/include/linux/usb/ch9.h

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

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