pullupmsg(9F)						   Kernel Functions for Drivers 					     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 concatenated.   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 device 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 successful, 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  encour-
       aged to use msgpullup(9F) instead of pullupmsg().

SunOS 5.10							    11 Nov 1996 						     pullupmsg(9F)