d556638404
refactored it to be a generic device. Instead of being part of the standard kernel, there is now a 'nvram' device for i386/amd64. It is in DEFAULTS like io and mem, and can be turned off with 'nodevice nvram'. This matches the previous behavior when it was first committed.
160 lines
4.4 KiB
C
160 lines
4.4 KiB
C
/*-
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* Copyright (c) 2007 Peter Wemm
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $FreeBSD$
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*/
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/kernel.h>
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#include <sys/conf.h>
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#include <sys/fcntl.h>
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#include <sys/proc.h>
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#include <sys/uio.h>
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#include <sys/module.h>
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#include <machine/clock.h>
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#include <isa/rtc.h>
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/*
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* Linux-style /dev/nvram driver
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*
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* cmos ram starts at bytes 14 through 128, for a total of 114 bytes.
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* The driver exposes byte 14 as file offset 0.
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*
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* Offsets 2 through 31 are checksummed at offset 32, 33.
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* In order to avoid the possibility of making the machine unbootable at the
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* bios level (press F1 to continue!), we refuse to allow writes if we do
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* not see a pre-existing valid checksum. If the existing sum is invalid,
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* then presumably we do not know how to make a sum that the bios will accept.
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*/
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#define NVRAM_FIRST RTC_DIAG /* 14 */
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#define NVRAM_LAST 128
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#define CKSUM_FIRST 2
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#define CKSUM_LAST 31
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#define CKSUM_MSB 32
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#define CKSUM_LSB 33
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static d_open_t nvram_open;
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static d_read_t nvram_read;
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static d_write_t nvram_write;
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static struct cdev *nvram_dev;
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static struct cdevsw nvram_cdevsw = {
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.d_version = D_VERSION,
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.d_flags = D_NEEDGIANT,
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.d_open = nvram_open,
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.d_read = nvram_read,
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.d_write = nvram_write,
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.d_name = "nvram",
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};
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static int
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nvram_open(struct cdev *dev __unused, int flags, int fmt __unused,
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struct thread *td)
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{
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int error = 0;
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if (flags & FWRITE)
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error = securelevel_gt(td->td_ucred, 0);
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return (error);
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}
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static int
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nvram_read(struct cdev *dev, struct uio *uio, int flags)
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{
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int nv_off;
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u_char v;
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int error = 0;
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while (uio->uio_resid > 0 && error == 0) {
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nv_off = uio->uio_offset + NVRAM_FIRST;
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if (nv_off < NVRAM_FIRST || nv_off >= NVRAM_LAST)
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return (0); /* Signal EOF */
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/* Single byte at a time */
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v = rtcin(nv_off);
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error = uiomove(&v, 1, uio);
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}
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return (error);
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}
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static int
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nvram_write(struct cdev *dev, struct uio *uio, int flags)
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{
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int nv_off;
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u_char v;
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int error = 0;
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int i;
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uint16_t sum;
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/* Assert that we understand the existing checksum first! */
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sum = rtcin(NVRAM_FIRST + CKSUM_MSB) << 8 |
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rtcin(NVRAM_FIRST + CKSUM_LSB);
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for (i = CKSUM_FIRST; i <= CKSUM_LAST; i++)
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sum -= rtcin(NVRAM_FIRST + i);
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if (sum != 0)
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return (EIO);
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/* Bring in user data and write */
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while (uio->uio_resid > 0 && error == 0) {
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nv_off = uio->uio_offset + NVRAM_FIRST;
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if (nv_off < NVRAM_FIRST || nv_off >= NVRAM_LAST)
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return (0); /* Signal EOF */
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/* Single byte at a time */
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error = uiomove(&v, 1, uio);
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writertc(nv_off, v);
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}
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/* Recalculate checksum afterwards */
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sum = 0;
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for (i = CKSUM_FIRST; i <= CKSUM_LAST; i++)
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sum += rtcin(NVRAM_FIRST + i);
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writertc(NVRAM_FIRST + CKSUM_MSB, sum >> 8);
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writertc(NVRAM_FIRST + CKSUM_LSB, sum);
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return (error);
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}
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static int
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nvram_modevent(module_t mod __unused, int type, void *data __unused)
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{
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switch (type) {
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case MOD_LOAD:
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nvram_dev = make_dev(&nvram_cdevsw, 0,
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UID_ROOT, GID_KMEM, 0640, "nvram");
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break;
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case MOD_UNLOAD:
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case MOD_SHUTDOWN:
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destroy_dev(nvram_dev);
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break;
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default:
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return (EOPNOTSUPP);
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}
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return (0);
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}
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DEV_MODULE(nvram, nvram_modevent, NULL);
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