// 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 */

  #ifdef CONFIG_X86

  /*
   * These functions are provided to be called internally or by other parts of
   * the kernel. It's up to the caller to ensure correct checksum before reading
   * or after writing (needs to be done only once).
   *
   * It is worth noting that these functions all access bytes of general
   * purpose memory in the NVRAM - that is to say, they all add the

   * NVRAM_FIRST_BYTE offset.  Pass them offsets into NVRAM as if you did not

   * know about the RTC cruft.
   */

  #define NVRAM_BYTES		(128 - NVRAM_FIRST_BYTE)
  
  /* Note that *all* calls to CMOS_READ and CMOS_WRITE must be done with
   * rtc_lock held. Due to the index-port/data-port design of the RTC, we
   * don't want two different things trying to get to it at once. (e.g. the
   * periodic 11 min sync from kernel/time/ntp.c vs. this driver.)
   */

  static unsigned char __nvram_read_byte(int i)

  {
  	return CMOS_READ(NVRAM_FIRST_BYTE + i);
  }

  static unsigned char pc_nvram_read_byte(int i)

  {
  	unsigned long flags;
  	unsigned char c;
  
  	spin_lock_irqsave(&rtc_lock, flags);
  	c = __nvram_read_byte(i);
  	spin_unlock_irqrestore(&rtc_lock, flags);
  	return c;
  }
  
  /* This races nicely with trying to read with checksum checking (nvram_read) */

  static void __nvram_write_byte(unsigned char c, int i)

  {
  	CMOS_WRITE(c, NVRAM_FIRST_BYTE + i);
  }

  static void pc_nvram_write_byte(unsigned char c, int i)

  {
  	unsigned long flags;
  
  	spin_lock_irqsave(&rtc_lock, flags);
  	__nvram_write_byte(c, i);
  	spin_unlock_irqrestore(&rtc_lock, flags);
  }

  /* On PCs, the checksum is built only over bytes 2..31 */
  #define PC_CKS_RANGE_START	2
  #define PC_CKS_RANGE_END	31
  #define PC_CKS_LOC		32

  static int __nvram_check_checksum(void)

  {

  	int i;
  	unsigned short sum = 0;
  	unsigned short expect;
  
  	for (i = PC_CKS_RANGE_START; i <= PC_CKS_RANGE_END; ++i)
  		sum += __nvram_read_byte(i);
  	expect = __nvram_read_byte(PC_CKS_LOC)<<8 |
  	    __nvram_read_byte(PC_CKS_LOC+1);
  	return (sum & 0xffff) == expect;

  }

  static void __nvram_set_checksum(void)

  {

  	int i;
  	unsigned short sum = 0;
  
  	for (i = PC_CKS_RANGE_START; i <= PC_CKS_RANGE_END; ++i)
  		sum += __nvram_read_byte(i);
  	__nvram_write_byte(sum >> 8, PC_CKS_LOC);
  	__nvram_write_byte(sum & 0xff, PC_CKS_LOC + 1);

  }

  static long pc_nvram_set_checksum(void)

  {

  	spin_lock_irq(&rtc_lock);
  	__nvram_set_checksum();
  	spin_unlock_irq(&rtc_lock);
  	return 0;
  }

  static long pc_nvram_initialize(void)
  {
  	ssize_t i;
  
  	spin_lock_irq(&rtc_lock);
  	for (i = 0; i < NVRAM_BYTES; ++i)
  		__nvram_write_byte(0, i);

  	__nvram_set_checksum();

  	spin_unlock_irq(&rtc_lock);
  	return 0;

  }

  static ssize_t pc_nvram_get_size(void)
  {
  	return NVRAM_BYTES;
  }

  static ssize_t pc_nvram_read(char *buf, size_t count, loff_t *ppos)
  {
  	char *p = buf;
  	loff_t i;
  
  	spin_lock_irq(&rtc_lock);
  	if (!__nvram_check_checksum()) {
  		spin_unlock_irq(&rtc_lock);
  		return -EIO;
  	}
  	for (i = *ppos; count > 0 && i < NVRAM_BYTES; --count, ++i, ++p)
  		*p = __nvram_read_byte(i);
  	spin_unlock_irq(&rtc_lock);
  
  	*ppos = i;
  	return p - buf;
  }
  
  static ssize_t pc_nvram_write(char *buf, size_t count, loff_t *ppos)
  {
  	char *p = buf;
  	loff_t i;
  
  	spin_lock_irq(&rtc_lock);
  	if (!__nvram_check_checksum()) {
  		spin_unlock_irq(&rtc_lock);
  		return -EIO;
  	}
  	for (i = *ppos; count > 0 && i < NVRAM_BYTES; --count, ++i, ++p)
  		__nvram_write_byte(*p, i);
  	__nvram_set_checksum();
  	spin_unlock_irq(&rtc_lock);
  
  	*ppos = i;
  	return p - buf;
  }

  const struct nvram_ops arch_nvram_ops = {

  	.read           = pc_nvram_read,
  	.write          = pc_nvram_write,

  	.read_byte      = pc_nvram_read_byte,
  	.write_byte     = pc_nvram_write_byte,
  	.get_size       = pc_nvram_get_size,

  	.set_checksum   = pc_nvram_set_checksum,
  	.initialize     = pc_nvram_initialize,

  };
  EXPORT_SYMBOL(arch_nvram_ops);
  #endif /* CONFIG_X86 */

  /*
   * The are the file operation function for user access to /dev/nvram
   */

  static loff_t nvram_misc_llseek(struct file *file, loff_t offset, int origin)

  {

  	return generic_file_llseek_size(file, offset, origin, MAX_LFS_FILESIZE,

  					nvram_size);

  }

  static ssize_t nvram_misc_read(struct file *file, char __user *buf,
  			       size_t count, loff_t *ppos)

  {

  	char *tmp;
  	ssize_t ret;

  	if (*ppos >= nvram_size)
  		return 0;

  	count = min_t(size_t, count, nvram_size - *ppos);
  	count = min_t(size_t, count, PAGE_SIZE);

  	tmp = kmalloc(count, GFP_KERNEL);
  	if (!tmp)
  		return -ENOMEM;

  	ret = nvram_read(tmp, count, ppos);
  	if (ret <= 0)
  		goto out;

  	if (copy_to_user(buf, tmp, ret)) {
  		*ppos -= ret;
  		ret = -EFAULT;
  	}

  out:
  	kfree(tmp);
  	return ret;

  }

  static ssize_t nvram_misc_write(struct file *file, const char __user *buf,
  				size_t count, loff_t *ppos)

  {

  	char *tmp;
  	ssize_t ret;

  	if (*ppos >= nvram_size)
  		return 0;

  	count = min_t(size_t, count, nvram_size - *ppos);
  	count = min_t(size_t, count, PAGE_SIZE);

  	tmp = memdup_user(buf, count);
  	if (IS_ERR(tmp))
  		return PTR_ERR(tmp);

  	ret = nvram_write(tmp, count, ppos);
  	kfree(tmp);
  	return ret;

  }

  static long nvram_misc_ioctl(struct file *file, unsigned int cmd,
  			     unsigned long arg)

  {

  	long ret = -ENOTTY;

  
  	switch (cmd) {

  #ifdef CONFIG_PPC
  	case OBSOLETE_PMAC_NVRAM_GET_OFFSET:
  		pr_warn("nvram: Using obsolete PMAC_NVRAM_GET_OFFSET ioctl
  ");

  		fallthrough;

  	case IOC_NVRAM_GET_OFFSET:
  		ret = -EINVAL;
  #ifdef CONFIG_PPC_PMAC
  		if (machine_is(powermac)) {
  			int part, offset;
  
  			if (copy_from_user(&part, (void __user *)arg,
  					   sizeof(part)) != 0)
  				return -EFAULT;
  			if (part < pmac_nvram_OF || part > pmac_nvram_NR)
  				return -EINVAL;
  			offset = pmac_get_partition(part);

  			if (offset < 0)
  				return -EINVAL;

  			if (copy_to_user((void __user *)arg,
  					 &offset, sizeof(offset)) != 0)
  				return -EFAULT;
  			ret = 0;
  		}
  #endif
  		break;

  #ifdef CONFIG_PPC32

  	case IOC_NVRAM_SYNC:
  		if (ppc_md.nvram_sync != NULL) {
  			mutex_lock(&nvram_mutex);
  			ppc_md.nvram_sync();
  			mutex_unlock(&nvram_mutex);
  		}
  		ret = 0;
  		break;

  #endif

  #elif defined(CONFIG_X86) || defined(CONFIG_M68K)

  	case NVRAM_INIT:
  		/* initialize NVRAM contents and checksum */
  		if (!capable(CAP_SYS_ADMIN))
  			return -EACCES;

  		if (arch_nvram_ops.initialize != NULL) {
  			mutex_lock(&nvram_mutex);
  			ret = arch_nvram_ops.initialize();
  			mutex_unlock(&nvram_mutex);
  		}
  		break;

  	case NVRAM_SETCKS:

  		/* just set checksum, contents unchanged (maybe useful after

  		 * checksum garbaged somehow...) */
  		if (!capable(CAP_SYS_ADMIN))
  			return -EACCES;

  		if (arch_nvram_ops.set_checksum != NULL) {
  			mutex_lock(&nvram_mutex);
  			ret = arch_nvram_ops.set_checksum();
  			mutex_unlock(&nvram_mutex);
  		}
  		break;

  #endif /* CONFIG_X86 || CONFIG_M68K */

  	}

  	return ret;

  }

  static int nvram_misc_open(struct inode *inode, struct file *file)

  {
  	spin_lock(&nvram_state_lock);

  	/* Prevent multiple readers/writers if desired. */

  	if ((nvram_open_cnt && (file->f_flags & O_EXCL)) ||

  	    (nvram_open_mode & NVRAM_EXCL)) {
  		spin_unlock(&nvram_state_lock);
  		return -EBUSY;
  	}

  #if defined(CONFIG_X86) || defined(CONFIG_M68K)

  	/* Prevent multiple writers if the set_checksum ioctl is implemented. */
  	if ((arch_nvram_ops.set_checksum != NULL) &&
  	    (file->f_mode & FMODE_WRITE) && (nvram_open_mode & NVRAM_WRITE)) {

  		spin_unlock(&nvram_state_lock);
  		return -EBUSY;
  	}

  #endif

  
  	if (file->f_flags & O_EXCL)
  		nvram_open_mode |= NVRAM_EXCL;

  	if (file->f_mode & FMODE_WRITE)

  		nvram_open_mode |= NVRAM_WRITE;
  	nvram_open_cnt++;
  
  	spin_unlock(&nvram_state_lock);
  
  	return 0;
  }

  static int nvram_misc_release(struct inode *inode, struct file *file)

  {
  	spin_lock(&nvram_state_lock);
  
  	nvram_open_cnt--;
  
  	/* if only one instance is open, clear the EXCL bit */
  	if (nvram_open_mode & NVRAM_EXCL)
  		nvram_open_mode &= ~NVRAM_EXCL;

  	if (file->f_mode & FMODE_WRITE)

  		nvram_open_mode &= ~NVRAM_WRITE;
  
  	spin_unlock(&nvram_state_lock);
  
  	return 0;
  }

  #if defined(CONFIG_X86) && defined(CONFIG_PROC_FS)

  static const char * const floppy_types[] = {

  	"none", "5.25'' 360k", "5.25'' 1.2M", "3.5'' 720k", "3.5'' 1.44M",
  	"3.5'' 2.88M", "3.5'' 2.88M"
  };

  static const char * const gfx_types[] = {

  	"EGA, VGA, ... (with BIOS)",
  	"CGA (40 cols)",
  	"CGA (80 cols)",
  	"monochrome",
  };

  static void pc_nvram_proc_read(unsigned char *nvram, struct seq_file *seq,
  			       void *offset)

  {
  	int checksum;
  	int type;
  
  	spin_lock_irq(&rtc_lock);
  	checksum = __nvram_check_checksum();
  	spin_unlock_irq(&rtc_lock);

  	seq_printf(seq, "Checksum status: %svalid
  ", checksum ? "" : "not ");

  	seq_printf(seq, "# floppies     : %d
  ",

  	    (nvram[6] & 1) ? (nvram[6] >> 6) + 1 : 0);

  	seq_printf(seq, "Floppy 0 type  : ");

  	type = nvram[2] >> 4;

  	if (type < ARRAY_SIZE(floppy_types))

  		seq_printf(seq, "%s
  ", floppy_types[type]);

  	else

  		seq_printf(seq, "%d (unknown)
  ", type);
  	seq_printf(seq, "Floppy 1 type  : ");

  	type = nvram[2] & 0x0f;

  	if (type < ARRAY_SIZE(floppy_types))

  		seq_printf(seq, "%s
  ", floppy_types[type]);

  	else

  		seq_printf(seq, "%d (unknown)
  ", type);

  	seq_printf(seq, "HD 0 type      : ");

  	type = nvram[4] >> 4;
  	if (type)

  		seq_printf(seq, "%02x
  ", type == 0x0f ? nvram[11] : type);

  	else

  		seq_printf(seq, "none
  ");

  	seq_printf(seq, "HD 1 type      : ");

  	type = nvram[4] & 0x0f;
  	if (type)

  		seq_printf(seq, "%02x
  ", type == 0x0f ? nvram[12] : type);

  	else

  		seq_printf(seq, "none
  ");

  	seq_printf(seq, "HD type 48 data: %d/%d/%d C/H/S, precomp %d, lz %d
  ",

  	    nvram[18] | (nvram[19] << 8),
  	    nvram[20], nvram[25],
  	    nvram[21] | (nvram[22] << 8), nvram[23] | (nvram[24] << 8));

  	seq_printf(seq, "HD type 49 data: %d/%d/%d C/H/S, precomp %d, lz %d
  ",

  	    nvram[39] | (nvram[40] << 8),
  	    nvram[41], nvram[46],
  	    nvram[42] | (nvram[43] << 8), nvram[44] | (nvram[45] << 8));

  	seq_printf(seq, "DOS base memory: %d kB
  ", nvram[7] | (nvram[8] << 8));
  	seq_printf(seq, "Extended memory: %d kB (configured), %d kB (tested)
  ",

  	    nvram[9] | (nvram[10] << 8), nvram[34] | (nvram[35] << 8));

  	seq_printf(seq, "Gfx adapter    : %s
  ",
  	    gfx_types[(nvram[6] >> 4) & 3]);

  	seq_printf(seq, "FPU            : %sinstalled
  ",

  	    (nvram[6] & 2) ? "" : "not ");

  	return;

  }

  static int nvram_proc_read(struct seq_file *seq, void *offset)
  {
  	unsigned char contents[NVRAM_BYTES];
  	int i = 0;
  
  	spin_lock_irq(&rtc_lock);
  	for (i = 0; i < NVRAM_BYTES; ++i)
  		contents[i] = __nvram_read_byte(i);
  	spin_unlock_irq(&rtc_lock);
  
  	pc_nvram_proc_read(contents, seq, offset);
  
  	return 0;
  }

  #endif /* CONFIG_X86 && CONFIG_PROC_FS */

  static const struct file_operations nvram_misc_fops = {
  	.owner		= THIS_MODULE,
  	.llseek		= nvram_misc_llseek,
  	.read		= nvram_misc_read,
  	.write		= nvram_misc_write,
  	.unlocked_ioctl	= nvram_misc_ioctl,
  	.open		= nvram_misc_open,
  	.release	= nvram_misc_release,
  };
  
  static struct miscdevice nvram_misc = {
  	NVRAM_MINOR,
  	"nvram",
  	&nvram_misc_fops,
  };
  
  static int __init nvram_module_init(void)
  {
  	int ret;

  	nvram_size = nvram_get_size();
  	if (nvram_size < 0)
  		return nvram_size;

  	ret = misc_register(&nvram_misc);
  	if (ret) {
  		pr_err("nvram: can't misc_register on minor=%d
  ", NVRAM_MINOR);
  		return ret;
  	}

  #if defined(CONFIG_X86) && defined(CONFIG_PROC_FS)

  	if (!proc_create_single("driver/nvram", 0, NULL, nvram_proc_read)) {
  		pr_err("nvram: can't create /proc/driver/nvram
  ");
  		misc_deregister(&nvram_misc);
  		return -ENOMEM;
  	}
  #endif
  
  	pr_info("Non-volatile memory driver v" NVRAM_VERSION "
  ");
  	return 0;
  }
  
  static void __exit nvram_module_exit(void)
  {

  #if defined(CONFIG_X86) && defined(CONFIG_PROC_FS)

  	remove_proc_entry("driver/nvram", NULL);
  #endif
  	misc_deregister(&nvram_misc);
  }
  
  module_init(nvram_module_init);
  module_exit(nvram_module_exit);

  MODULE_LICENSE("GPL");

  MODULE_ALIAS_MISCDEV(NVRAM_MINOR);

  MODULE_ALIAS("devname:nvram");