summaryrefslogtreecommitdiff
path: root/drivers/char/nvram.c
blob: adcc213c331e4040fe42de858db531fc91aaed89 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
/*
 * 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>


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 (!access_ok(buf, count))
		return -EFAULT;
	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 (!access_ok(buf, count))
		return -EFAULT;
	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) {
	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;
	}
	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;
	}

	/* 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;
	}

	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\n", checksum ? "" : "not ");

	seq_printf(seq, "# floppies     : %d\n",
	    (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\n", floppy_types[type]);
	else
		seq_printf(seq, "%d (unknown)\n", type);
	seq_printf(seq, "Floppy 1 type  : ");
	type = nvram[2] & 0x0f;
	if (type < ARRAY_SIZE(floppy_types))
		seq_printf(seq, "%s\n", floppy_types[type]);
	else
		seq_printf(seq, "%d (unknown)\n", type);

	seq_printf(seq, "HD 0 type      : ");
	type = nvram[4] >> 4;
	if (type)
		seq_printf(seq, "%02x\n", type == 0x0f ? nvram[11] : type);
	else
		seq_printf(seq, "none\n");

	seq_printf(seq, "HD 1 type      : ");
	type = nvram[4] & 0x0f;
	if (type)
		seq_printf(seq, "%02x\n", type == 0x0f ? nvram[12] : type);
	else
		seq_printf(seq, "none\n");

	seq_printf(seq, "HD type 48 data: %d/%d/%d C/H/S, precomp %d, lz %d\n",
	    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\n",
	    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\n", nvram[7] | (nvram[8] << 8));
	seq_printf(seq, "Extended memory: %d kB (configured), %d kB (tested)\n",
	    nvram[9] | (nvram[10] << 8), nvram[34] | (nvram[35] << 8));

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

	seq_printf(seq, "FPU            : %sinstalled\n",
	    (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\n", 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\n");
		misc_deregister(&nvram_misc);
		return -ENOMEM;
	}
#endif

	pr_info("Non-volatile memory driver v" NVRAM_VERSION "\n");
	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);