Kernel Functions for Drivers     usbgetcurrentframenumber(9F)



NAME
     usbgetcurrentframenumber - Return  current  logical  usb
     frame number

SYNOPSIS
     #include 



     usbframenumbert usbgetcurrentframenumber(devinfot *dip);


INTERFACE LEVEL
     Solaris DI specific (Solaris DI)

PARAMETERS
     dip    Pointer to the device's devinfo structure.


DESCRIPTION
     The usbgetcurrentframenumber()  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 isochro-
     nous request.


     The USB specification requires that the frame frequency (the
     period  between  start-of-frame packets) is one millisecond.
     The Solaris operating 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  usbgetcurrentframenumber()   function
     returns  the current USB frame number. On failure it returns
     0. The function fails if dip is NUL.

CONTEXT
     May be called from user, kernel or interrupt context.

EXAMPLES
           usbpipehandlet handle;
           usbframenumbert offset = 10;
           usbisocreqt *isocreq;

           isocreq = usballocisocreq(...);
             ...



SunOS 5.11          Last change: 25 July 2004                   1






Kernel Functions for Drivers     usbgetcurrentframenumber(9F)



             ...
           isocreq->isocframeno = usbgetcurrentframenumber(dip) ] offset;
           isocreq->isocattributes = USBATRSISOCSTARTFRAME;
             ...
             ...
           if (usbpipeisocxfer(handle, isocreq, 0) != USBSUCES) {
             ...
           }


ATRIBUTES
     See attributes(5) for descriptions of the  following  attri-
     butes:



     
           ATRIBUTE TYPE               ATRIBUTE VALUE       
    
     Architecture                 PCI-based systems           
    
     Interface stability          Committed                   
    
     Availability                 SUNWusb                     
    


SEE ALSO
     attributes(5),                       usballocisocreq(9F),
     usbgetmaxpktsperisocrequest(9F),
     usbpipeisocxfer(9F),
     usbpipegetmaxbulktransfersize(9F),
     usbisocrequest(9S)






















SunOS 5.11          Last change: 25 July 2004                   2