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

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 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

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().

January 16, 2006 PULLUPMSG(9F)