linux-imx

// SPDX-License-Identifier: GPL-2.0-only

/*

 * CMOS/NV-RAM driver for Linux

 *

 * Copyright (C) 1997 Roman Hodek <Roman.Hodek@informatik.uni-erlangen.de>

 * idea by and with help from Richard Jelinek <rj@suse.de>

 * Portions copyright (c) 2001,2002 Sun Microsystems (thockin@sun.com)

 *

 * This driver allows you to access the contents of the non-volatile memory in

 * the mc146818rtc.h real-time clock. This chip is built into all PCs and into

 * many Atari machines. In the former it's called "CMOS-RAM", in the latter

 * "NVRAM" (NV stands for non-volatile).

 *

 * The data are supplied as a (seekable) character device, /dev/nvram. The

 * size of this file is dependent on the controller.  The usual size is 114,

 * the number of freely available bytes in the memory (i.e., not used by the

 * RTC itself).

 *

 * Checksums over the NVRAM contents are managed by this driver. In case of a

 * bad checksum, reads and writes return -EIO. The checksum can be initialized

 * to a sane state either by ioctl(NVRAM_INIT) (clear whole NVRAM) or

 * ioctl(NVRAM_SETCKS) (doesn't change contents, just makes checksum valid

 * again; use with care!)

 *

 *  1.1 Cesar Barros: SMP locking fixes

 *      added changelog

 *  1.2 Erik Gilling: Cobalt Networks support

 *      Tim Hockin: general cleanup, Cobalt support

 *  1.3 Wim Van Sebroeck: convert PRINT_PROC to seq_file

 */

​

#define NVRAM_VERSION   "1.3"

​

#include <linux/module.h>

#include <linux/nvram.h>

#include <linux/types.h>

#include <linux/errno.h>

#include <linux/miscdevice.h>

#include <linux/ioport.h>

#include <linux/fcntl.h>

#include <linux/mc146818rtc.h>

#include <linux/init.h>

#include <linux/proc_fs.h>

#include <linux/seq_file.h>

#include <linux/slab.h>

#include <linux/spinlock.h>

#include <linux/io.h>

#include <linux/uaccess.h>

#include <linux/mutex.h>

#include <linux/pagemap.h>

​

#ifdef CONFIG_PPC

#include <asm/nvram.h>

#endif

​

static DEFINE_MUTEX(nvram_mutex);

static DEFINE_SPINLOCK(nvram_state_lock);

static int nvram_open_cnt;  /* #times opened */

static int nvram_open_mode; /* special open modes */

static ssize_t nvram_size;

#define NVRAM_WRITE     1 /* opened for writing (exclusive) */

#define NVRAM_EXCL      2 /* opened with O_EXCL */

​