pullupmsg(9F)

NAME

     pullupmsg - concatenate bytes in a message

SYNOPSIS

     #include <sys/stream.h>

     int pullupmsg(mblk_t *mp, ssize_t len);

INTERFACE LEVEL

     Architecture independent level 1 (DDI/DKI).

PARAMETERS

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

     len   Number of bytes to concatenate.

DESCRIPTION

     pullupmsg() 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

     pullupmsg() can be called from user or interrupt 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
     M_DATA 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.
      Otherwise, 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.

      1 xxxwsrv(q)
      2    queue_t *q;
      3 {
      4       mblk_t *mp;
      5       mblk_t *tmp;
      6       caddr_t dma_addr;
      7     ssize_t dma_len;
      8
      9       while ((mp = getq(q)) != NULL) {
     10               switch (mp->b_datap->db_type) {
     11             case M_DATA:
     12                      if (pullupmsg(mp, -1)) {
     13                            dma_addr = vtop(mp->b_rptr);
     14                              dma_len = mp->b_wptr - mp->b_rptr;
     15                              xxx_do_dma(dma_addr, dma_len);
     16                              freemsg(mp);
     17                              break;
     18                      }
     19                      for (tmp = mp; tmp; tmp = tmp->b_cont) {
     20                            dma_addr = vtop(tmp->b_rptr);
     21                            dma_len = tmp->b_wptr - tmp->b_rptr;
     22                            xxx_do_dma(dma_addr, dma_len);
     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

     pullupmsg() 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 pul-
     lupmsg().