usr/src/uts/common/io/pipemod.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License, Version 1.0 only
   6  * (the "License").  You may not use this file except in compliance
   7  * with the License.
   8  *
   9  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
  10  * or http://www.opensolaris.org/os/licensing.
  11  * See the License for the specific language governing permissions
  12  * and limitations under the License.
  13  *
  14  * When distributing Covered Code, include this CDDL HEADER in each
  15  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  16  * If applicable, add the following below this CDDL HEADER, with the
  17  * fields enclosed by brackets "[]" replaced with your own identifying
  18  * information: Portions Copyright [yyyy] [name of copyright owner]
  19  *
  20  * CDDL HEADER END
  21  */
  22 /*
  23  * Copyright (c) 1997, by Sun Microsystems, Inc.
  24  * All rights reserved.
  25  */
  26
  27 /*      Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
  28 /*        All Rights Reserved   */
  29
  30
  31 #pragma ident   "%Z%%M% %I%     %E% SMI"
  32
  33 /*
  34  * This module switches the read and write flush bits for each
  35  * M_FLUSH control message it receives. It's intended usage is to
  36  * properly flush a STREAMS-based pipe.
  37  */
  38 #include <sys/types.h>
  39 #include <sys/param.h>
  40 #include <sys/errno.h>
  41 #include <sys/stream.h>
  42 #include <sys/stropts.h>
  43
  44 #include <sys/conf.h>
  45 #include <sys/modctl.h>
  46
  47 /*ARGSUSED*/
  48 static int
  49 pipeopen(queue_t *rqp, dev_t *devp, int flag, int sflag, cred_t *crp)
  50 {
  51         qprocson(rqp);
  52         return (0);
  53 }
  54
  55 /*ARGSUSED*/
  56 static int
  57 pipeclose(queue_t *q, int cflag, cred_t *crp)
  58 {
  59         qprocsoff(q);
  60         return (0);
  61 }
  62
  63 /*
  64  * Use same put procedure for write and read queues.
  65  * If mp is an M_FLUSH message, switch the FLUSHW to FLUSHR and
  66  * the FLUSHR to FLUSHW and send the message on.  If mp is not an
  67  * M_FLUSH message, send it on with out processing.
  68  */
  69 static int
  70 pipeput(queue_t *qp, mblk_t *mp)
  71 {
  72         switch (mp->b_datap->db_type) {
  73         case M_FLUSH:
  74                 if (!(*mp->b_rptr & FLUSHR && *mp->b_rptr & FLUSHW)) {
  75                         if (*mp->b_rptr & FLUSHW) {
  76                                 *mp->b_rptr |= FLUSHR;
  77                                 *mp->b_rptr &= ~FLUSHW;
  78                         } else {
  79                                 *mp->b_rptr |= FLUSHW;
  80                                 *mp->b_rptr &= ~FLUSHR;
  81                         }
  82                 }
  83                 break;
  84
  85         default:
  86                 break;
  87         }
  88         putnext(qp, mp);
  89         return (0);
  90 }
  91
  92 static struct module_info pipe_info = {
  93         1003, "pipemod", 0, INFPSZ, STRHIGH, STRLOW
  94 };
  95
  96 static struct qinit piperinit = {
  97         pipeput, NULL, pipeopen, pipeclose, NULL, &pipe_info, NULL
  98 };
  99
 100 static struct qinit pipewinit = {
 101         pipeput, NULL, NULL, NULL, NULL, &pipe_info, NULL
 102 };
 103
 104 static struct streamtab pipeinfo = { &piperinit, &pipewinit, NULL, NULL };
 105
 106 static struct fmodsw fsw = {
 107         "pipemod",
 108         &pipeinfo,
 109         D_NEW | D_MP
 110 };
 111
 112 static struct modlstrmod modlstrmod = {
 113         &mod_strmodops, "pipe flushing module", &fsw
 114 };
 115
 116 static struct modlinkage modlinkage = {
 117         MODREV_1, &modlstrmod, NULL
 118 };
 119
 120 int
 121 _init(void)
 122 {
 123         return (mod_install(&modlinkage));
 124 }
 125
 126 int
 127 _fini(void)
 128 {
 129         return (mod_remove(&modlinkage));
 130 }
 131
 132 int
 133 _info(struct modinfo *modinfop)
 134 {
 135         return (mod_info(&modlinkage, modinfop));
 136 }