source: bootcd/isolinux/syslinux-6.03/com32/lib/sys/opendev.c

/* ----------------------------------------------------------------------- *
 *
 *   Copyright 2003-2008 H. Peter Anvin - All Rights Reserved
 *
 *   Permission is hereby granted, free of charge, to any person
 *   obtaining a copy of this software and associated documentation
 *   files (the "Software"), to deal in the Software without
 *   restriction, including without limitation the rights to use,
 *   copy, modify, merge, publish, distribute, sublicense, and/or
 *   sell copies of the Software, and to permit persons to whom
 *   the Software is furnished to do so, subject to the following
 *   conditions:
 *
 *   The above copyright notice and this permission notice shall
 *   be included in all copies or substantial portions of the Software.
 *
 *   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 *   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 *   OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 *   NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 *   HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 *   WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 *   FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 *   OTHER DEALINGS IN THE SOFTWARE.
 *
 * ----------------------------------------------------------------------- */

#include <errno.h>
#include <com32.h>
#include <string.h>
#include <unistd.h>
#include "file.h"

/*
 * opendev.c
 *
 * Open a special device
 */

int opendev(const struct input_dev *idev,
            const struct output_dev *odev, int flags)
{
    int fd;
    struct file_info *fp;
    int okflags;
    int e;

    okflags = (idev ? idev->fileflags : 0) | (odev ? odev->fileflags : 0);

    if (!(flags & 3) || (flags & ~okflags)) {
        errno = EINVAL;
        return -1;
    }

    for (fd = 0, fp = __file_info; fd < NFILES; fd++, fp++)
        if (!fp->iop && !fp->oop)
            break;

    if (fd >= NFILES) {
        errno = EMFILE;
        return -1;
    }

    /* The file structure is already zeroed */
    fp->iop = &dev_error_r;
    fp->oop = &dev_error_w;
    fp->i.datap = fp->i.buf;

    if (idev) {
        if (idev->open && (e = idev->open(fp))) {
            errno = e;
            goto puke;
        }
        fp->iop = idev;
    }

    while (odev) {
        if (odev->open && (e = odev->open(fp))) {
            if (e == EAGAIN) {
                if (odev->fallback) {
                    odev = odev->fallback;
                    continue;
                } else {
                    e = EIO;
                }
            }
            errno = e;
            goto puke;
        }
        fp->oop = odev;
        break;
    }

    return fd;

puke:
    close(fd);
    return -1;
}