Kernel Functions for Drivers                        pullupmsg(9F)



NAME
     pullupmsg - concatenate bytes in a message

SYNOPSIS
     #include 



     int pullupmsg(mblkt *mp, ssizet len);


INTERFACE LEVEL
     Architecture independent level 1 (DI/DKI).

PARAMETERS
     mp     Pointer to the message whose blocks are  to  be  con-
            catenated.  mblkt  is  an  instance  of the msgb(9S)
            structure.


     len    Number of bytes to concatenate.


DESCRIPTION
     The pullupmsg() function  tries  to  combine  multiple  data
     blocks  into  a  single  block. pullupmsg() concatenates and
     aligns the first len data bytes of the message pointed to by
     mp.  If  len  equals  -1,  all data are concatenated. If len
     bytes of the same message type cannot be found,  pullupmsg()
     fails and returns 0.

RETURN VALUES
     On success, 1 is returned; on failure, 0 is returned.

CONTEXT
     The pullupmsg() function can be called from user, interrupt,
     or kernel context.

EXAMPLES
     Example 1 Using pullupmsg()


     This is a driver write srv(9E) (service) routine for a  dev-
     ice  that  does  not  support  scatter/gather  DMA.  For all
     MDATA messages, the data will be transferred to the  device
     with DMA. First, try to pull up the message into one message
     block with the pullupmsg() function (line 12).  If  success-
     ful, the transfer can be accomplished in one DMA job. Other-
     wise, it must be done one message block  at  a  time  (lines
     19-22).  After  the data has been transferred to the device,
     free the message and continue  processing  messages  on  the
     queue.



SunOS 5.11          Last change: 16 Jan 2006                    1






Kernel Functions for Drivers                        pullupmsg(9F)




        1 xxxwsrv(q)
        2    queuet *q;
        3 {
        4       mblkt *mp;
        5       mblkt *tmp;
        6       caddrt dmaaddr;
        7     ssizet dmalen;
        8
        9       while ((mp = getq(q)) != NUL) {
       10               switch (mp->bdatap->dbtype) {
       11             case MDATA:
       12                      if (pullupmsg(mp, -1)) {
       13                            dmaaddr = vtop(mp->brptr);
       14                              dmalen = mp->bwptr - mp->brptr;
       15                              xxxdodma(dmaaddr, dmalen);
       16                              freemsg(mp);
       17                              break;
       18                      }
       19                      for (tmp = mp; tmp; tmp = tmp->bcont) {
       20                            dmaaddr = vtop(tmp->brptr);
       21                            dmalen = tmp->bwptr - tmp->brptr;
       22                            xxxdodma(dmaaddr, dmalen);
       23                    }
       24                      freemsg(mp);
       25                      break;
                  . . .
       26                }
       27       }
       28 }


SEE ALSO
     srv(9E), allocb(9F), msgpullup(9F), msgb(9S)


     Writing Device Drivers


     STREAMS Programming Guide

NOTES
     The pullupmsg() function is not included in the DKI and will
     be  removed  from  the  system  in  a future release. Device
     driver writers are strongly encouraged to use  msgpullup(9F)
     instead of pullupmsg().









SunOS 5.11          Last change: 16 Jan 2006                    2