1 /*- 2 * Copyright (c) 2000 Mark R. V. Murray & Jeroen C. van Gelderen 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer 10 * in this position and unchanged. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR 16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 * 26 * $FreeBSD$ 27 */ 28 29 #include <sys/param.h> 30 #include <sys/systm.h> 31 #include <sys/conf.h> 32 #include <sys/uio.h> 33 #include <sys/kernel.h> 34 #include <sys/malloc.h> 35 #include <sys/module.h> 36 #include <sys/bus.h> 37 #include <machine/bus.h> 38 #include <machine/resource.h> 39 #include <sys/rman.h> 40 41 /* For use with destroy_dev(9). */ 42 static dev_t null_dev; 43 static dev_t zero_dev; 44 45 static d_write_t null_write; 46 static d_read_t zero_read; 47 48 #define CDEV_MAJOR 2 49 #define NULL_MINOR 2 50 #define ZERO_MINOR 12 51 52 static struct cdevsw null_cdevsw = { 53 /* open */ (d_open_t *)nullop, 54 /* close */ (d_close_t *)nullop, 55 /* read */ (d_read_t *)nullop, 56 /* write */ null_write, 57 /* ioctl */ noioctl, 58 /* poll */ nopoll, 59 /* mmap */ nommap, 60 /* strategy */ nostrategy, 61 /* name */ "null", 62 /* maj */ CDEV_MAJOR, 63 /* dump */ nodump, 64 /* psize */ nopsize, 65 /* flags */ 0, 66 }; 67 68 static struct cdevsw zero_cdevsw = { 69 /* open */ (d_open_t *)nullop, 70 /* close */ (d_close_t *)nullop, 71 /* read */ zero_read, 72 /* write */ null_write, 73 /* ioctl */ noioctl, 74 /* poll */ nopoll, 75 /* mmap */ nommap, 76 /* strategy */ nostrategy, 77 /* name */ "zero", 78 /* maj */ CDEV_MAJOR, 79 /* dump */ nodump, 80 /* psize */ nopsize, 81 /* flags */ D_MMAP_ANON, 82 }; 83 84 static void *zbuf; 85 86 static int 87 null_write(dev_t dev, struct uio *uio, int flag) 88 { 89 uio->uio_resid = 0; 90 return 0; 91 } 92 93 static int 94 zero_read(dev_t dev, struct uio *uio, int flag) 95 { 96 u_int c; 97 int error = 0; 98 99 while (uio->uio_resid > 0 && error == 0) { 100 c = min(uio->uio_resid, PAGE_SIZE); 101 error = uiomove(zbuf, c, uio); 102 } 103 return error; 104 } 105 106 static int 107 null_modevent(module_t mod, int type, void *data) 108 { 109 switch(type) { 110 case MOD_LOAD: 111 if (bootverbose) 112 printf("null: <null device, zero device>\n"); 113 zbuf = (void *)malloc(PAGE_SIZE, M_TEMP, M_WAITOK | M_ZERO); 114 zero_dev = make_dev(&zero_cdevsw, ZERO_MINOR, UID_ROOT, 115 GID_WHEEL, 0666, "zero"); 116 null_dev = make_dev(&null_cdevsw, NULL_MINOR, UID_ROOT, 117 GID_WHEEL, 0666, "null"); 118 return 0; 119 120 case MOD_UNLOAD: 121 destroy_dev(null_dev); 122 destroy_dev(zero_dev); 123 free(zbuf, M_TEMP); 124 return 0; 125 126 case MOD_SHUTDOWN: 127 return 0; 128 129 default: 130 return EOPNOTSUPP; 131 } 132 } 133 134 DEV_MODULE(null, null_modevent, NULL); 135