USB_GET_CURRENT_FRAME_NUMBER(9F) Kernel Functions for Drivers USB_GET_CURRENT_FRAME_NUMBER(9F)

usb_get_current_frame_number - Return current logical usb frame number

#include <sys/usb/usba.h>
usb_frame_number_t usb_get_current_frame_number(dev_info_t *dip);

illumos DDI specific (illumos DDI)

dip
Pointer to the device's dev_info structure.

The usb_get_current_frame_number() function retrieves the current logical USB frame number.

Isochronous requests can be started on a particular numbered frame. An offset number of frames (typically between 4 and 10) can be added to the current logical frame number to specify the number of an upcoming frame to start an isochronous request.

The USB specification requires that the frame frequency (the period between start-of-frame packets) is one millisecond. The illumos operating environment USB implementation uses a running counter of the number of milliseconds since boot as the current logical frame number.

On success, the usb_get_current_frame_number() function returns the current USB frame number. On failure it returns 0. The function fails if dip is NULL.

May be called from user, kernel or interrupt context.


    usb_pipe_handle_t handle;
    usb_frame_number_t offset = 10;
    usb_isoc_req_t *isoc_req;
    isoc_req = usb_alloc_isoc_req(...);
      ...
      ...
    isoc_req->isoc_frame_no = usb_get_current_frame_number(dip) + offset;
    isoc_req->isoc_attributes = USB_ATTRS_ISOC_START_FRAME;
      ...
      ...
    if (usb_pipe_isoc_xfer(handle, isoc_req, 0) != USB_SUCCESS) {
      ...
    }

See attributes(5) for descriptions of the following attributes:

ATTRIBUTE TYPE ATTRIBUTE VALUE
Architecture PCI-based systems
Interface stability Committed

attributes(5), usb_alloc_isoc_req(9F), usb_get_max_pkts_per_isoc_request(9F), usb_pipe_isoc_xfer(9F), usb_pipe_get_max_bulk_transfer_size(9F), usb_isoc_request(9S)
July 25, 2004 OmniOS