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Annotation of prex-old/dev/gen/null.c, Revision 1.1

1.1     ! nbrk        1: /*-
        !             2:  * Copyright (c) 2005-2006, Kohsuke Ohtani
        !             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:  * 2. Redistributions in binary form must reproduce the above copyright
        !            11:  *    notice, this list of conditions and the following disclaimer in the
        !            12:  *    documentation and/or other materials provided with the distribution.
        !            13:  * 3. Neither the name of the author nor the names of any co-contributors
        !            14:  *    may be used to endorse or promote products derived from this software
        !            15:  *    without specific prior written permission.
        !            16:  *
        !            17:  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
        !            18:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
        !            19:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
        !            20:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
        !            21:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
        !            22:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
        !            23:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
        !            24:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
        !            25:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
        !            26:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
        !            27:  * SUCH DAMAGE.
        !            28:  */
        !            29:
        !            30: /*
        !            31:  * null.c - null device
        !            32:  */
        !            33:
        !            34: #include <driver.h>
        !            35:
        !            36: static int null_read(device_t dev, char *buf, size_t *nbyte, int blkno);
        !            37: static int null_write(device_t dev, char *buf, size_t *nbyte, int blkno);
        !            38: static int null_init(void);
        !            39:
        !            40: /*
        !            41:  * Driver structure
        !            42:  */
        !            43: struct driver null_drv = {
        !            44:        /* name */      "NULL device",
        !            45:        /* order */     2,
        !            46:        /* init */      null_init,
        !            47: };
        !            48:
        !            49: static struct devio null_io = {
        !            50:        /* open */      NULL,
        !            51:        /* close */     NULL,
        !            52:        /* read */      null_read,
        !            53:        /* write */     null_write,
        !            54:        /* ioctl */     NULL,
        !            55:        /* event */     NULL,
        !            56: };
        !            57:
        !            58: static device_t null_dev;      /* Device object */
        !            59:
        !            60: /*
        !            61:  * Always returns 0 bytes as the read size.
        !            62:  */
        !            63: static int
        !            64: null_read(device_t dev, char *buf, size_t *nbyte, int blkno)
        !            65: {
        !            66:
        !            67:        *nbyte = 0;
        !            68:        return 0;
        !            69: }
        !            70:
        !            71: /*
        !            72:  * Data written to this device is discarded.
        !            73:  */
        !            74: static int
        !            75: null_write(device_t dev, char *buf, size_t *nbyte, int blkno)
        !            76: {
        !            77:
        !            78:        return 0;
        !            79: }
        !            80:
        !            81:
        !            82: /*
        !            83:  * Initialize
        !            84:  */
        !            85: static int
        !            86: null_init(void)
        !            87: {
        !            88:
        !            89:        /* Create device object */
        !            90:        null_dev = device_create(&null_io, "null", DF_CHR);
        !            91:        ASSERT(null_dev);
        !            92:        return 0;
        !            93: }