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

NAME

       usb_get_current_frame_number - Return current logical usb frame number

SYNOPSIS

       #include <sys/usb/usba.h>

       usb_frame_number_t usb_get_current_frame_number(dev_info_t *dip);

INTERFACE LEVEL

       Solaris DDI specific (Solaris DDI)

PARAMETERS

       dip

	   Pointer to the device's dev_info structure.

DESCRIPTION

       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 Solaris  oper-
       ating environment USB implementation uses a running counter of the number of milliseconds since boot as the current logical frame number.

RETURN VALUES

       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.

CONTEXT

       May be called from user, kernel or interrupt context.

EXAMPLES

	   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) {
	     ...
	   }

ATTRIBUTES

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

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Architecture		     |PCI-based systems 	   |
       +-----------------------------+-----------------------------+
       |Interface stability	     |Evolving			   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWusb			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       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_trans-
       fer_size(9F), usb_isoc_request(9S)

SunOS 5.10							   25 July 2004 				  usb_get_current_frame_number(9F)