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author | markm <markm@FreeBSD.org> | 2000-06-25 08:32:39 +0000 |
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committer | markm <markm@FreeBSD.org> | 2000-06-25 08:32:39 +0000 |
commit | 58318db80801eb90db1a44822cdb52018a3a0cad (patch) | |
tree | 680f13e0271e2357a03a324bbd3bf21d82f92c05 /sys/dev/null | |
parent | b2db9a0f361aa06b3371f9567693e9614186279a (diff) | |
download | FreeBSD-src-58318db80801eb90db1a44822cdb52018a3a0cad.zip FreeBSD-src-58318db80801eb90db1a44822cdb52018a3a0cad.tar.gz |
New machine independant /dev/null and /dev/zero driver. This device is
severely stripped down compared with its predecessor, and is measurably
a _lot_ faster.
Many thanks to Jeroen van Gelderen for lots of good ideas.
There is still a problem with this; it is written as a mudule, and as
such is theoretically unloadable. However, there is no refcounting done
as I would prefer to do that a'la device_busy(9), rather than some
"home-rolled" scheme. The point is pretty moot, as /dev/null is
effectively compulsory.
Reviewed by: dfr
Diffstat (limited to 'sys/dev/null')
-rw-r--r-- | sys/dev/null/null.c | 137 |
1 files changed, 137 insertions, 0 deletions
diff --git a/sys/dev/null/null.c b/sys/dev/null/null.c new file mode 100644 index 0000000..bbc610e --- /dev/null +++ b/sys/dev/null/null.c @@ -0,0 +1,137 @@ +/*- + * Copyright (c) 2000 Mark R. V. Murray & Jeroen C. van Gelderen + * 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 + * in this position and unchanged. + * 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 AUTHORS ``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 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. + * + * $FreeBSD$ + */ + +#include <sys/param.h> +#include <sys/systm.h> +#include <sys/conf.h> +#include <sys/uio.h> +#include <sys/kernel.h> +#include <sys/malloc.h> +#include <sys/module.h> +#include <sys/bus.h> +#include <machine/bus.h> +#include <machine/resource.h> +#include <sys/rman.h> + +/* For use with destroy_dev(9). */ +static dev_t null_dev; +static dev_t zero_dev; + +static d_read_t nullwrite; +static d_read_t zeroread; + +#define CDEV_MAJOR 2 +#define NULL_MINOR 2 +#define ZERO_MINOR 12 + +static struct cdevsw null_cdevsw = { + /* open */ (d_open_t *)nullop, + /* close */ (d_close_t *)nullop, + /* read */ (d_read_t *)nullop, + /* write */ nullwrite, + /* ioctl */ noioctl, + /* poll */ nopoll, + /* mmap */ nommap, + /* strategy */ nostrategy, + /* name */ "null", + /* maj */ CDEV_MAJOR, + /* dump */ nodump, + /* psize */ nopsize, + /* flags */ 0, + /* bmaj */ -1 +}; + +static struct cdevsw zero_cdevsw = { + /* open */ (d_open_t *)nullop, + /* close */ (d_close_t *)nullop, + /* read */ zeroread, + /* write */ nullwrite, + /* ioctl */ noioctl, + /* poll */ nopoll, + /* mmap */ nommap, + /* strategy */ nostrategy, + /* name */ "zero", + /* maj */ CDEV_MAJOR, + /* dump */ nodump, + /* psize */ nopsize, + /* flags */ D_MMAP_ANON, + /* bmaj */ -1 +}; + +static void *zbuf; + +static int +nullwrite(dev_t dev, struct uio *uio, int flag) +{ + uio->uio_resid = 0; + return 0; +} + +static int +zeroread(dev_t dev, struct uio *uio, int flag) +{ + u_int c; + int error = 0; + + while (uio->uio_resid > 0 && error == 0) { + c = min(uio->uio_resid, PAGE_SIZE); + error = uiomove(zbuf, c, uio); + } + return error; +} + +static int +null_modevent(module_t mod, int type, void *data) +{ + switch(type) { + case MOD_LOAD: + if (bootverbose) + printf("nulldev: <null device, zero device>\n"); + zbuf = (void *)malloc(PAGE_SIZE, M_TEMP, M_WAITOK); + bzero(zbuf, PAGE_SIZE); + zero_dev = make_dev(&zero_cdevsw, ZERO_MINOR, UID_ROOT, + GID_WHEEL, 0666, "zero"); + null_dev = make_dev(&null_cdevsw, NULL_MINOR, UID_ROOT, + GID_WHEEL, 0666, "null"); + return 0; + + case MOD_UNLOAD: + destroy_dev(null_dev); + destroy_dev(zero_dev); + free(zbuf, M_TEMP); + return 0; + + case MOD_SHUTDOWN: + return 0; + + default: + return EOPNOTSUPP; + } +} + +DEV_MODULE(nulldev, null_modevent, NULL); |