Standard Device Requests

To query or set a particular configuration or alternate setting there exist a number functions. These commonly used functions setup standard device requests (control transfers for a specified device:

• int usb_set_configuration(struct usb_device *dev, int configuration);

  To activate a particular configuration use this function.
  The argument is of
  0 <= configuration < dev->descriptor.bNumConfigurations.
  Configuration 0 is selected by default after the device is attached to the bus.

• int usb_set_interface(struct usb_device *dev, int interface, int alternate);

  This function activates an alternate setting of a specified interface. The argument interface is of
  0 <= interface < dev->actconfig->bNumInterfaces.
  The argument alternate is of
  0 <= alternate < dev->actconfig->interface[interface].num_altsetting

• int usb_get_device_descriptor(struct usb_device *dev);

  This function rereads the complete descriptor tree from a particular device. It is called automatically whenever a device is attached to the bus or it may be called whenever a USB descriptor has changed.

• int usb_get_descriptor(struct usb_device *dev, unsigned char desctype, unsigned char descindex, void *buf, int size);

  Single USB descriptors can be read as raw data from a device. This function can be used to parse extended or vendor specific descriptors. The arguments desctype and descindex are documented in [4] section 9.4.3 and 9.5.

• int usb_get_string(struct usb_device *dev, unsigned short langid, unsigned char index, void *buf, int size);

  If a device, configuration or interface descriptor references a string index value (see [4] section 9.6.5) this function can be used to retrieve the string descriptor. According to the specification USB strings are coded as Unicode. If successful the function returns 0 otherwise an error code is returned.

• int usb_string(struct usb_device *dev, int index, char *buf, size_t size);

  This function simplifies usb_get_string by converting Unicode strings into ASCII strings.

• int usb_get_status(struct usb_device *dev, int type, int target, void *data);

  This USB control request is documented in [4] section 9.4.5.

• int usb_clear_halt(struct usb_device *dev, int pipe);

  If an endpoint is stalled (see [4] chapter 8.4.4) call this function to clear the STALL condition. STALL indicates that a function is unable to transmit or receive data, or that a control pipe request is not supported. The argument endpoint defines a pipe handle.

• int usb_get_protocol(struct usb_device *dev, int ifnum);

  This HID USB control request is documented in [6] section 7.2.5.

• int usb_set_protocol(struct usb_device *dev, int protocol, int ifnum); This HID USB control request is documented in [6] section 7.2.6.

• int usb_get_report(struct usb_device *dev, unsigned char type, unsigned char id, int ifnum, void *buf, int size);

  This HID USB control request is documented in [6] section 7.2.1

• int usb_set_idle(struct usb_device *dev, int ifnum, int duration, int report_id);

  This HID USB control request is documented in [6] section 7.2.4