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 GuideNOTES
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)
