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/*-
* Copyright (c) 2007 Peter Wemm
* 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 AND CONTRIBUTORS ``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.
*
* $FreeBSD$
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/conf.h>
#include <sys/fcntl.h>
#include <sys/lock.h>
#include <sys/proc.h>
#include <sys/sx.h>
#include <sys/uio.h>
#include <sys/module.h>
#include <isa/rtc.h>
/*
* Linux-style /dev/nvram driver
*
* cmos ram starts at bytes 14 through 128, for a total of 114 bytes.
* The driver exposes byte 14 as file offset 0.
*
* Offsets 2 through 31 are checksummed at offset 32, 33.
* In order to avoid the possibility of making the machine unbootable at the
* bios level (press F1 to continue!), we refuse to allow writes if we do
* not see a pre-existing valid checksum. If the existing sum is invalid,
* then presumably we do not know how to make a sum that the bios will accept.
*/
#define NVRAM_FIRST RTC_DIAG /* 14 */
#define NVRAM_LAST 128
#define CKSUM_FIRST 2
#define CKSUM_LAST 31
#define CKSUM_MSB 32
#define CKSUM_LSB 33
static d_open_t nvram_open;
static d_read_t nvram_read;
static d_write_t nvram_write;
static struct cdev *nvram_dev;
static struct sx nvram_lock;
static struct cdevsw nvram_cdevsw = {
.d_version = D_VERSION,
.d_open = nvram_open,
.d_read = nvram_read,
.d_write = nvram_write,
.d_name = "nvram",
};
static int
nvram_open(struct cdev *dev __unused, int flags, int fmt __unused,
struct thread *td)
{
int error = 0;
if (flags & FWRITE)
error = securelevel_gt(td->td_ucred, 0);
return (error);
}
static int
nvram_read(struct cdev *dev, struct uio *uio, int flags)
{
int nv_off;
u_char v;
int error = 0;
while (uio->uio_resid > 0 && error == 0) {
nv_off = uio->uio_offset + NVRAM_FIRST;
if (nv_off < NVRAM_FIRST || nv_off >= NVRAM_LAST)
return (0); /* Signal EOF */
/* Single byte at a time */
v = rtcin(nv_off);
error = uiomove(&v, 1, uio);
}
return (error);
}
static int
nvram_write(struct cdev *dev, struct uio *uio, int flags)
{
int nv_off;
u_char v;
int error = 0;
int i;
uint16_t sum;
sx_xlock(&nvram_lock);
/* Assert that we understand the existing checksum first! */
sum = rtcin(NVRAM_FIRST + CKSUM_MSB) << 8 |
rtcin(NVRAM_FIRST + CKSUM_LSB);
for (i = CKSUM_FIRST; i <= CKSUM_LAST; i++)
sum -= rtcin(NVRAM_FIRST + i);
if (sum != 0) {
sx_xunlock(&nvram_lock);
return (EIO);
}
/* Bring in user data and write */
while (uio->uio_resid > 0 && error == 0) {
nv_off = uio->uio_offset + NVRAM_FIRST;
if (nv_off < NVRAM_FIRST || nv_off >= NVRAM_LAST) {
sx_xunlock(&nvram_lock);
return (0); /* Signal EOF */
}
/* Single byte at a time */
error = uiomove(&v, 1, uio);
writertc(nv_off, v);
}
/* Recalculate checksum afterwards */
sum = 0;
for (i = CKSUM_FIRST; i <= CKSUM_LAST; i++)
sum += rtcin(NVRAM_FIRST + i);
writertc(NVRAM_FIRST + CKSUM_MSB, sum >> 8);
writertc(NVRAM_FIRST + CKSUM_LSB, sum);
sx_xunlock(&nvram_lock);
return (error);
}
static int
nvram_modevent(module_t mod __unused, int type, void *data __unused)
{
switch (type) {
case MOD_LOAD:
sx_init(&nvram_lock, "nvram");
nvram_dev = make_dev(&nvram_cdevsw, 0,
UID_ROOT, GID_KMEM, 0640, "nvram");
break;
case MOD_UNLOAD:
case MOD_SHUTDOWN:
destroy_dev(nvram_dev);
sx_destroy(&nvram_lock);
break;
default:
return (EOPNOTSUPP);
}
return (0);
}
DEV_MODULE(nvram, nvram_modevent, NULL);
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