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Annotation of prex/dev/gen/zero.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:  * zero.c - zero device
        !            32:  */
        !            33:
        !            34: #include <driver.h>
        !            35:
        !            36: static int zero_read(device_t, char *, size_t *, int);
        !            37: static int zero_write(device_t, char *, size_t *, int);
        !            38: static int zero_init(void);
        !            39:
        !            40: /*
        !            41:  * Driver structure
        !            42:  */
        !            43: struct driver zero_drv = {
        !            44:        /* name */      "Zero device",
        !            45:        /* order */     2,
        !            46:        /* init */      zero_init,
        !            47: };
        !            48:
        !            49: /*
        !            50:  * Device I/O table
        !            51:  */
        !            52: static struct devio zero_io = {
        !            53:        /* open */      NULL,
        !            54:        /* close */     NULL,
        !            55:        /* read */      zero_read,
        !            56:        /* write */     zero_write,
        !            57:        /* ioctl */     NULL,
        !            58:        /* event */     NULL,
        !            59: };
        !            60:
        !            61: static device_t zero_dev;      /* Device object */
        !            62:
        !            63: /*
        !            64:  * Read
        !            65:  */
        !            66: static int
        !            67: zero_read(device_t dev, char *buf, size_t *nbyte, int blkno)
        !            68: {
        !            69:        void *kbuf;
        !            70:
        !            71:        /* Translate buffer address to kernel address */
        !            72:        kbuf = kmem_map(buf, *nbyte);
        !            73:        if (kbuf == NULL)
        !            74:                return EFAULT;
        !            75:        memset(kbuf, 0, *nbyte);
        !            76:        return 0;
        !            77: }
        !            78:
        !            79: /*
        !            80:  * Writing data to this device is ignored.
        !            81:  */
        !            82: static int
        !            83: zero_write(device_t dev, char *buf, size_t *nbyte, int blkno)
        !            84: {
        !            85:
        !            86:        return 0;
        !            87: }
        !            88:
        !            89:
        !            90: /*
        !            91:  * Initialize
        !            92:  */
        !            93: static int
        !            94: zero_init(void)
        !            95: {
        !            96:
        !            97:        /* Create device object */
        !            98:        zero_dev = device_create(&zero_io, "zero", DF_CHR);
        !            99:        ASSERT(zero_dev);
        !           100:        return 0;
        !           101: }