/*      $NetBSD: devnull.c,v 1.8 2018/09/03 16:29:37 riastradh Exp $    */

/*
* Copyright (c) 2009 Antti Kantee.  All Rights Reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
* OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/

/*
* /dev/null, the infamous bytesink.
*
* I can't imagine it being very different in the rump kernel than in
* the host kernel.  But nonetheless it serves as a simple example.
*/

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: devnull.c,v 1.8 2018/09/03 16:29:37 riastradh Exp $");

#include <sys/param.h>
#include <sys/conf.h>
#include <sys/device.h>
#include <sys/stat.h>

#include <rump-sys/vfs.h>

static dev_type_open(rump_devnullopen);
static dev_type_read(rump_devnullrw);

static struct cdevsw null_cdevsw = {
       .d_open = rump_devnullopen,
       .d_close = nullclose,
       .d_read = rump_devnullrw,
       .d_write = rump_devnullrw,
       .d_ioctl = noioctl,
       .d_stop = nostop,
       .d_tty = notty,
       .d_poll = nopoll,
       .d_mmap = nommap,
       .d_kqfilter = nokqfilter,
       .d_discard = nodiscard,
       .d_flag = D_OTHER | D_MPSAFE
};

int
rump_devnull_init()
{
       devmajor_t null_bmaj, null_cmaj;
       int error;

       null_bmaj = null_cmaj = NODEVMAJOR;
       error = devsw_attach("null", NULL, &null_bmaj, &null_cdevsw,&null_cmaj);
       KASSERT(error || null_cmaj == 2);

       error = rump_vfs_makeonedevnode(S_IFCHR,
           "/dev/null", null_cmaj, DEV_NULL);
       if (error)
               return error;
       return rump_vfs_makeonedevnode(S_IFCHR,
           "/dev/zero", null_cmaj, DEV_ZERO);
}

static int
rump_devnullopen(dev_t dev, int flag, int mode, struct lwp *l)
{

       if (minor(dev) == DEV_ZERO || minor(dev) == DEV_NULL)
               return 0;
       return ENXIO;
}

static int
rump_devnullrw(dev_t dev, struct uio *uio, int flags)
{
       char zeros[512];
       int error;

       switch (minor(dev)) {
       case DEV_NULL:
               if (uio->uio_rw == UIO_WRITE)
                       uio->uio_resid = 0;
               break;
       case DEV_ZERO:
               if (uio->uio_rw == UIO_WRITE) {
                       uio->uio_resid = 0;
                       break;
               }
               memset(zeros, 0, sizeof(zeros));
               while (uio->uio_resid > 0) {
                       error = uiomove(zeros,
                           uimin(sizeof(zeros), uio->uio_resid), uio);
                       if (error)
                               return error;
               }
               break;
       default:
               return ENXIO; /* how? */
       }

       return 0;
}