xref: /linux/drivers/firmware/dmi_scan.c (revision 0d456bad36d42d16022be045c8a53ddbb59ee478)
1 #include <linux/types.h>
2 #include <linux/string.h>
3 #include <linux/init.h>
4 #include <linux/module.h>
5 #include <linux/ctype.h>
6 #include <linux/dmi.h>
7 #include <linux/efi.h>
8 #include <linux/bootmem.h>
9 #include <linux/random.h>
10 #include <asm/dmi.h>
11 
12 /*
13  * DMI stands for "Desktop Management Interface".  It is part
14  * of and an antecedent to, SMBIOS, which stands for System
15  * Management BIOS.  See further: http://www.dmtf.org/standards
16  */
17 static char dmi_empty_string[] = "        ";
18 
19 /*
20  * Catch too early calls to dmi_check_system():
21  */
22 static int dmi_initialized;
23 
24 static const char * __init dmi_string_nosave(const struct dmi_header *dm, u8 s)
25 {
26 	const u8 *bp = ((u8 *) dm) + dm->length;
27 
28 	if (s) {
29 		s--;
30 		while (s > 0 && *bp) {
31 			bp += strlen(bp) + 1;
32 			s--;
33 		}
34 
35 		if (*bp != 0) {
36 			size_t len = strlen(bp)+1;
37 			size_t cmp_len = len > 8 ? 8 : len;
38 
39 			if (!memcmp(bp, dmi_empty_string, cmp_len))
40 				return dmi_empty_string;
41 			return bp;
42 		}
43 	}
44 
45 	return "";
46 }
47 
48 static char * __init dmi_string(const struct dmi_header *dm, u8 s)
49 {
50 	const char *bp = dmi_string_nosave(dm, s);
51 	char *str;
52 	size_t len;
53 
54 	if (bp == dmi_empty_string)
55 		return dmi_empty_string;
56 
57 	len = strlen(bp) + 1;
58 	str = dmi_alloc(len);
59 	if (str != NULL)
60 		strcpy(str, bp);
61 	else
62 		printk(KERN_ERR "dmi_string: cannot allocate %Zu bytes.\n", len);
63 
64 	return str;
65 }
66 
67 /*
68  *	We have to be cautious here. We have seen BIOSes with DMI pointers
69  *	pointing to completely the wrong place for example
70  */
71 static void dmi_table(u8 *buf, int len, int num,
72 		      void (*decode)(const struct dmi_header *, void *),
73 		      void *private_data)
74 {
75 	u8 *data = buf;
76 	int i = 0;
77 
78 	/*
79 	 *	Stop when we see all the items the table claimed to have
80 	 *	OR we run off the end of the table (also happens)
81 	 */
82 	while ((i < num) && (data - buf + sizeof(struct dmi_header)) <= len) {
83 		const struct dmi_header *dm = (const struct dmi_header *)data;
84 
85 		/*
86 		 *  We want to know the total length (formatted area and
87 		 *  strings) before decoding to make sure we won't run off the
88 		 *  table in dmi_decode or dmi_string
89 		 */
90 		data += dm->length;
91 		while ((data - buf < len - 1) && (data[0] || data[1]))
92 			data++;
93 		if (data - buf < len - 1)
94 			decode(dm, private_data);
95 		data += 2;
96 		i++;
97 	}
98 }
99 
100 static u32 dmi_base;
101 static u16 dmi_len;
102 static u16 dmi_num;
103 
104 static int __init dmi_walk_early(void (*decode)(const struct dmi_header *,
105 		void *))
106 {
107 	u8 *buf;
108 
109 	buf = dmi_ioremap(dmi_base, dmi_len);
110 	if (buf == NULL)
111 		return -1;
112 
113 	dmi_table(buf, dmi_len, dmi_num, decode, NULL);
114 
115 	add_device_randomness(buf, dmi_len);
116 
117 	dmi_iounmap(buf, dmi_len);
118 	return 0;
119 }
120 
121 static int __init dmi_checksum(const u8 *buf)
122 {
123 	u8 sum = 0;
124 	int a;
125 
126 	for (a = 0; a < 15; a++)
127 		sum += buf[a];
128 
129 	return sum == 0;
130 }
131 
132 static char *dmi_ident[DMI_STRING_MAX];
133 static LIST_HEAD(dmi_devices);
134 int dmi_available;
135 
136 /*
137  *	Save a DMI string
138  */
139 static void __init dmi_save_ident(const struct dmi_header *dm, int slot, int string)
140 {
141 	const char *d = (const char*) dm;
142 	char *p;
143 
144 	if (dmi_ident[slot])
145 		return;
146 
147 	p = dmi_string(dm, d[string]);
148 	if (p == NULL)
149 		return;
150 
151 	dmi_ident[slot] = p;
152 }
153 
154 static void __init dmi_save_uuid(const struct dmi_header *dm, int slot, int index)
155 {
156 	const u8 *d = (u8*) dm + index;
157 	char *s;
158 	int is_ff = 1, is_00 = 1, i;
159 
160 	if (dmi_ident[slot])
161 		return;
162 
163 	for (i = 0; i < 16 && (is_ff || is_00); i++) {
164 		if(d[i] != 0x00) is_ff = 0;
165 		if(d[i] != 0xFF) is_00 = 0;
166 	}
167 
168 	if (is_ff || is_00)
169 		return;
170 
171 	s = dmi_alloc(16*2+4+1);
172 	if (!s)
173 		return;
174 
175 	sprintf(s, "%pUB", d);
176 
177         dmi_ident[slot] = s;
178 }
179 
180 static void __init dmi_save_type(const struct dmi_header *dm, int slot, int index)
181 {
182 	const u8 *d = (u8*) dm + index;
183 	char *s;
184 
185 	if (dmi_ident[slot])
186 		return;
187 
188 	s = dmi_alloc(4);
189 	if (!s)
190 		return;
191 
192 	sprintf(s, "%u", *d & 0x7F);
193 	dmi_ident[slot] = s;
194 }
195 
196 static void __init dmi_save_one_device(int type, const char *name)
197 {
198 	struct dmi_device *dev;
199 
200 	/* No duplicate device */
201 	if (dmi_find_device(type, name, NULL))
202 		return;
203 
204 	dev = dmi_alloc(sizeof(*dev) + strlen(name) + 1);
205 	if (!dev) {
206 		printk(KERN_ERR "dmi_save_one_device: out of memory.\n");
207 		return;
208 	}
209 
210 	dev->type = type;
211 	strcpy((char *)(dev + 1), name);
212 	dev->name = (char *)(dev + 1);
213 	dev->device_data = NULL;
214 	list_add(&dev->list, &dmi_devices);
215 }
216 
217 static void __init dmi_save_devices(const struct dmi_header *dm)
218 {
219 	int i, count = (dm->length - sizeof(struct dmi_header)) / 2;
220 
221 	for (i = 0; i < count; i++) {
222 		const char *d = (char *)(dm + 1) + (i * 2);
223 
224 		/* Skip disabled device */
225 		if ((*d & 0x80) == 0)
226 			continue;
227 
228 		dmi_save_one_device(*d & 0x7f, dmi_string_nosave(dm, *(d + 1)));
229 	}
230 }
231 
232 static void __init dmi_save_oem_strings_devices(const struct dmi_header *dm)
233 {
234 	int i, count = *(u8 *)(dm + 1);
235 	struct dmi_device *dev;
236 
237 	for (i = 1; i <= count; i++) {
238 		char *devname = dmi_string(dm, i);
239 
240 		if (devname == dmi_empty_string)
241 			continue;
242 
243 		dev = dmi_alloc(sizeof(*dev));
244 		if (!dev) {
245 			printk(KERN_ERR
246 			   "dmi_save_oem_strings_devices: out of memory.\n");
247 			break;
248 		}
249 
250 		dev->type = DMI_DEV_TYPE_OEM_STRING;
251 		dev->name = devname;
252 		dev->device_data = NULL;
253 
254 		list_add(&dev->list, &dmi_devices);
255 	}
256 }
257 
258 static void __init dmi_save_ipmi_device(const struct dmi_header *dm)
259 {
260 	struct dmi_device *dev;
261 	void * data;
262 
263 	data = dmi_alloc(dm->length);
264 	if (data == NULL) {
265 		printk(KERN_ERR "dmi_save_ipmi_device: out of memory.\n");
266 		return;
267 	}
268 
269 	memcpy(data, dm, dm->length);
270 
271 	dev = dmi_alloc(sizeof(*dev));
272 	if (!dev) {
273 		printk(KERN_ERR "dmi_save_ipmi_device: out of memory.\n");
274 		return;
275 	}
276 
277 	dev->type = DMI_DEV_TYPE_IPMI;
278 	dev->name = "IPMI controller";
279 	dev->device_data = data;
280 
281 	list_add_tail(&dev->list, &dmi_devices);
282 }
283 
284 static void __init dmi_save_dev_onboard(int instance, int segment, int bus,
285 					int devfn, const char *name)
286 {
287 	struct dmi_dev_onboard *onboard_dev;
288 
289 	onboard_dev = dmi_alloc(sizeof(*onboard_dev) + strlen(name) + 1);
290 	if (!onboard_dev) {
291 		printk(KERN_ERR "dmi_save_dev_onboard: out of memory.\n");
292 		return;
293 	}
294 	onboard_dev->instance = instance;
295 	onboard_dev->segment = segment;
296 	onboard_dev->bus = bus;
297 	onboard_dev->devfn = devfn;
298 
299 	strcpy((char *)&onboard_dev[1], name);
300 	onboard_dev->dev.type = DMI_DEV_TYPE_DEV_ONBOARD;
301 	onboard_dev->dev.name = (char *)&onboard_dev[1];
302 	onboard_dev->dev.device_data = onboard_dev;
303 
304 	list_add(&onboard_dev->dev.list, &dmi_devices);
305 }
306 
307 static void __init dmi_save_extended_devices(const struct dmi_header *dm)
308 {
309 	const u8 *d = (u8*) dm + 5;
310 
311 	/* Skip disabled device */
312 	if ((*d & 0x80) == 0)
313 		return;
314 
315 	dmi_save_dev_onboard(*(d+1), *(u16 *)(d+2), *(d+4), *(d+5),
316 			     dmi_string_nosave(dm, *(d-1)));
317 	dmi_save_one_device(*d & 0x7f, dmi_string_nosave(dm, *(d - 1)));
318 }
319 
320 /*
321  *	Process a DMI table entry. Right now all we care about are the BIOS
322  *	and machine entries. For 2.5 we should pull the smbus controller info
323  *	out of here.
324  */
325 static void __init dmi_decode(const struct dmi_header *dm, void *dummy)
326 {
327 	switch(dm->type) {
328 	case 0:		/* BIOS Information */
329 		dmi_save_ident(dm, DMI_BIOS_VENDOR, 4);
330 		dmi_save_ident(dm, DMI_BIOS_VERSION, 5);
331 		dmi_save_ident(dm, DMI_BIOS_DATE, 8);
332 		break;
333 	case 1:		/* System Information */
334 		dmi_save_ident(dm, DMI_SYS_VENDOR, 4);
335 		dmi_save_ident(dm, DMI_PRODUCT_NAME, 5);
336 		dmi_save_ident(dm, DMI_PRODUCT_VERSION, 6);
337 		dmi_save_ident(dm, DMI_PRODUCT_SERIAL, 7);
338 		dmi_save_uuid(dm, DMI_PRODUCT_UUID, 8);
339 		break;
340 	case 2:		/* Base Board Information */
341 		dmi_save_ident(dm, DMI_BOARD_VENDOR, 4);
342 		dmi_save_ident(dm, DMI_BOARD_NAME, 5);
343 		dmi_save_ident(dm, DMI_BOARD_VERSION, 6);
344 		dmi_save_ident(dm, DMI_BOARD_SERIAL, 7);
345 		dmi_save_ident(dm, DMI_BOARD_ASSET_TAG, 8);
346 		break;
347 	case 3:		/* Chassis Information */
348 		dmi_save_ident(dm, DMI_CHASSIS_VENDOR, 4);
349 		dmi_save_type(dm, DMI_CHASSIS_TYPE, 5);
350 		dmi_save_ident(dm, DMI_CHASSIS_VERSION, 6);
351 		dmi_save_ident(dm, DMI_CHASSIS_SERIAL, 7);
352 		dmi_save_ident(dm, DMI_CHASSIS_ASSET_TAG, 8);
353 		break;
354 	case 10:	/* Onboard Devices Information */
355 		dmi_save_devices(dm);
356 		break;
357 	case 11:	/* OEM Strings */
358 		dmi_save_oem_strings_devices(dm);
359 		break;
360 	case 38:	/* IPMI Device Information */
361 		dmi_save_ipmi_device(dm);
362 		break;
363 	case 41:	/* Onboard Devices Extended Information */
364 		dmi_save_extended_devices(dm);
365 	}
366 }
367 
368 static void __init print_filtered(const char *info)
369 {
370 	const char *p;
371 
372 	if (!info)
373 		return;
374 
375 	for (p = info; *p; p++)
376 		if (isprint(*p))
377 			printk(KERN_CONT "%c", *p);
378 		else
379 			printk(KERN_CONT "\\x%02x", *p & 0xff);
380 }
381 
382 static void __init dmi_dump_ids(void)
383 {
384 	const char *board;	/* Board Name is optional */
385 
386 	printk(KERN_DEBUG "DMI: ");
387 	print_filtered(dmi_get_system_info(DMI_SYS_VENDOR));
388 	printk(KERN_CONT " ");
389 	print_filtered(dmi_get_system_info(DMI_PRODUCT_NAME));
390 	board = dmi_get_system_info(DMI_BOARD_NAME);
391 	if (board) {
392 		printk(KERN_CONT "/");
393 		print_filtered(board);
394 	}
395 	printk(KERN_CONT ", BIOS ");
396 	print_filtered(dmi_get_system_info(DMI_BIOS_VERSION));
397 	printk(KERN_CONT " ");
398 	print_filtered(dmi_get_system_info(DMI_BIOS_DATE));
399 	printk(KERN_CONT "\n");
400 }
401 
402 static int __init dmi_present(const char __iomem *p)
403 {
404 	u8 buf[15];
405 
406 	memcpy_fromio(buf, p, 15);
407 	if ((memcmp(buf, "_DMI_", 5) == 0) && dmi_checksum(buf)) {
408 		dmi_num = (buf[13] << 8) | buf[12];
409 		dmi_len = (buf[7] << 8) | buf[6];
410 		dmi_base = (buf[11] << 24) | (buf[10] << 16) |
411 			(buf[9] << 8) | buf[8];
412 
413 		/*
414 		 * DMI version 0.0 means that the real version is taken from
415 		 * the SMBIOS version, which we don't know at this point.
416 		 */
417 		if (buf[14] != 0)
418 			printk(KERN_INFO "DMI %d.%d present.\n",
419 			       buf[14] >> 4, buf[14] & 0xF);
420 		else
421 			printk(KERN_INFO "DMI present.\n");
422 		if (dmi_walk_early(dmi_decode) == 0) {
423 			dmi_dump_ids();
424 			return 0;
425 		}
426 	}
427 	return 1;
428 }
429 
430 void __init dmi_scan_machine(void)
431 {
432 	char __iomem *p, *q;
433 	int rc;
434 
435 	if (efi_enabled) {
436 		if (efi.smbios == EFI_INVALID_TABLE_ADDR)
437 			goto error;
438 
439 		/* This is called as a core_initcall() because it isn't
440 		 * needed during early boot.  This also means we can
441 		 * iounmap the space when we're done with it.
442 		 */
443 		p = dmi_ioremap(efi.smbios, 32);
444 		if (p == NULL)
445 			goto error;
446 
447 		rc = dmi_present(p + 0x10); /* offset of _DMI_ string */
448 		dmi_iounmap(p, 32);
449 		if (!rc) {
450 			dmi_available = 1;
451 			goto out;
452 		}
453 	}
454 	else {
455 		/*
456 		 * no iounmap() for that ioremap(); it would be a no-op, but
457 		 * it's so early in setup that sucker gets confused into doing
458 		 * what it shouldn't if we actually call it.
459 		 */
460 		p = dmi_ioremap(0xF0000, 0x10000);
461 		if (p == NULL)
462 			goto error;
463 
464 		for (q = p; q < p + 0x10000; q += 16) {
465 			rc = dmi_present(q);
466 			if (!rc) {
467 				dmi_available = 1;
468 				dmi_iounmap(p, 0x10000);
469 				goto out;
470 			}
471 		}
472 		dmi_iounmap(p, 0x10000);
473 	}
474  error:
475 	printk(KERN_INFO "DMI not present or invalid.\n");
476  out:
477 	dmi_initialized = 1;
478 }
479 
480 /**
481  *	dmi_matches - check if dmi_system_id structure matches system DMI data
482  *	@dmi: pointer to the dmi_system_id structure to check
483  */
484 static bool dmi_matches(const struct dmi_system_id *dmi)
485 {
486 	int i;
487 
488 	WARN(!dmi_initialized, KERN_ERR "dmi check: not initialized yet.\n");
489 
490 	for (i = 0; i < ARRAY_SIZE(dmi->matches); i++) {
491 		int s = dmi->matches[i].slot;
492 		if (s == DMI_NONE)
493 			break;
494 		if (dmi_ident[s]
495 		    && strstr(dmi_ident[s], dmi->matches[i].substr))
496 			continue;
497 		/* No match */
498 		return false;
499 	}
500 	return true;
501 }
502 
503 /**
504  *	dmi_is_end_of_table - check for end-of-table marker
505  *	@dmi: pointer to the dmi_system_id structure to check
506  */
507 static bool dmi_is_end_of_table(const struct dmi_system_id *dmi)
508 {
509 	return dmi->matches[0].slot == DMI_NONE;
510 }
511 
512 /**
513  *	dmi_check_system - check system DMI data
514  *	@list: array of dmi_system_id structures to match against
515  *		All non-null elements of the list must match
516  *		their slot's (field index's) data (i.e., each
517  *		list string must be a substring of the specified
518  *		DMI slot's string data) to be considered a
519  *		successful match.
520  *
521  *	Walk the blacklist table running matching functions until someone
522  *	returns non zero or we hit the end. Callback function is called for
523  *	each successful match. Returns the number of matches.
524  */
525 int dmi_check_system(const struct dmi_system_id *list)
526 {
527 	int count = 0;
528 	const struct dmi_system_id *d;
529 
530 	for (d = list; !dmi_is_end_of_table(d); d++)
531 		if (dmi_matches(d)) {
532 			count++;
533 			if (d->callback && d->callback(d))
534 				break;
535 		}
536 
537 	return count;
538 }
539 EXPORT_SYMBOL(dmi_check_system);
540 
541 /**
542  *	dmi_first_match - find dmi_system_id structure matching system DMI data
543  *	@list: array of dmi_system_id structures to match against
544  *		All non-null elements of the list must match
545  *		their slot's (field index's) data (i.e., each
546  *		list string must be a substring of the specified
547  *		DMI slot's string data) to be considered a
548  *		successful match.
549  *
550  *	Walk the blacklist table until the first match is found.  Return the
551  *	pointer to the matching entry or NULL if there's no match.
552  */
553 const struct dmi_system_id *dmi_first_match(const struct dmi_system_id *list)
554 {
555 	const struct dmi_system_id *d;
556 
557 	for (d = list; !dmi_is_end_of_table(d); d++)
558 		if (dmi_matches(d))
559 			return d;
560 
561 	return NULL;
562 }
563 EXPORT_SYMBOL(dmi_first_match);
564 
565 /**
566  *	dmi_get_system_info - return DMI data value
567  *	@field: data index (see enum dmi_field)
568  *
569  *	Returns one DMI data value, can be used to perform
570  *	complex DMI data checks.
571  */
572 const char *dmi_get_system_info(int field)
573 {
574 	return dmi_ident[field];
575 }
576 EXPORT_SYMBOL(dmi_get_system_info);
577 
578 /**
579  * dmi_name_in_serial - Check if string is in the DMI product serial information
580  * @str: string to check for
581  */
582 int dmi_name_in_serial(const char *str)
583 {
584 	int f = DMI_PRODUCT_SERIAL;
585 	if (dmi_ident[f] && strstr(dmi_ident[f], str))
586 		return 1;
587 	return 0;
588 }
589 
590 /**
591  *	dmi_name_in_vendors - Check if string is in the DMI system or board vendor name
592  *	@str: 	Case sensitive Name
593  */
594 int dmi_name_in_vendors(const char *str)
595 {
596 	static int fields[] = { DMI_SYS_VENDOR, DMI_BOARD_VENDOR, DMI_NONE };
597 	int i;
598 	for (i = 0; fields[i] != DMI_NONE; i++) {
599 		int f = fields[i];
600 		if (dmi_ident[f] && strstr(dmi_ident[f], str))
601 			return 1;
602 	}
603 	return 0;
604 }
605 EXPORT_SYMBOL(dmi_name_in_vendors);
606 
607 /**
608  *	dmi_find_device - find onboard device by type/name
609  *	@type: device type or %DMI_DEV_TYPE_ANY to match all device types
610  *	@name: device name string or %NULL to match all
611  *	@from: previous device found in search, or %NULL for new search.
612  *
613  *	Iterates through the list of known onboard devices. If a device is
614  *	found with a matching @vendor and @device, a pointer to its device
615  *	structure is returned.  Otherwise, %NULL is returned.
616  *	A new search is initiated by passing %NULL as the @from argument.
617  *	If @from is not %NULL, searches continue from next device.
618  */
619 const struct dmi_device * dmi_find_device(int type, const char *name,
620 				    const struct dmi_device *from)
621 {
622 	const struct list_head *head = from ? &from->list : &dmi_devices;
623 	struct list_head *d;
624 
625 	for(d = head->next; d != &dmi_devices; d = d->next) {
626 		const struct dmi_device *dev =
627 			list_entry(d, struct dmi_device, list);
628 
629 		if (((type == DMI_DEV_TYPE_ANY) || (dev->type == type)) &&
630 		    ((name == NULL) || (strcmp(dev->name, name) == 0)))
631 			return dev;
632 	}
633 
634 	return NULL;
635 }
636 EXPORT_SYMBOL(dmi_find_device);
637 
638 /**
639  *	dmi_get_date - parse a DMI date
640  *	@field:	data index (see enum dmi_field)
641  *	@yearp: optional out parameter for the year
642  *	@monthp: optional out parameter for the month
643  *	@dayp: optional out parameter for the day
644  *
645  *	The date field is assumed to be in the form resembling
646  *	[mm[/dd]]/yy[yy] and the result is stored in the out
647  *	parameters any or all of which can be omitted.
648  *
649  *	If the field doesn't exist, all out parameters are set to zero
650  *	and false is returned.  Otherwise, true is returned with any
651  *	invalid part of date set to zero.
652  *
653  *	On return, year, month and day are guaranteed to be in the
654  *	range of [0,9999], [0,12] and [0,31] respectively.
655  */
656 bool dmi_get_date(int field, int *yearp, int *monthp, int *dayp)
657 {
658 	int year = 0, month = 0, day = 0;
659 	bool exists;
660 	const char *s, *y;
661 	char *e;
662 
663 	s = dmi_get_system_info(field);
664 	exists = s;
665 	if (!exists)
666 		goto out;
667 
668 	/*
669 	 * Determine year first.  We assume the date string resembles
670 	 * mm/dd/yy[yy] but the original code extracted only the year
671 	 * from the end.  Keep the behavior in the spirit of no
672 	 * surprises.
673 	 */
674 	y = strrchr(s, '/');
675 	if (!y)
676 		goto out;
677 
678 	y++;
679 	year = simple_strtoul(y, &e, 10);
680 	if (y != e && year < 100) {	/* 2-digit year */
681 		year += 1900;
682 		if (year < 1996)	/* no dates < spec 1.0 */
683 			year += 100;
684 	}
685 	if (year > 9999)		/* year should fit in %04d */
686 		year = 0;
687 
688 	/* parse the mm and dd */
689 	month = simple_strtoul(s, &e, 10);
690 	if (s == e || *e != '/' || !month || month > 12) {
691 		month = 0;
692 		goto out;
693 	}
694 
695 	s = e + 1;
696 	day = simple_strtoul(s, &e, 10);
697 	if (s == y || s == e || *e != '/' || day > 31)
698 		day = 0;
699 out:
700 	if (yearp)
701 		*yearp = year;
702 	if (monthp)
703 		*monthp = month;
704 	if (dayp)
705 		*dayp = day;
706 	return exists;
707 }
708 EXPORT_SYMBOL(dmi_get_date);
709 
710 /**
711  *	dmi_walk - Walk the DMI table and get called back for every record
712  *	@decode: Callback function
713  *	@private_data: Private data to be passed to the callback function
714  *
715  *	Returns -1 when the DMI table can't be reached, 0 on success.
716  */
717 int dmi_walk(void (*decode)(const struct dmi_header *, void *),
718 	     void *private_data)
719 {
720 	u8 *buf;
721 
722 	if (!dmi_available)
723 		return -1;
724 
725 	buf = ioremap(dmi_base, dmi_len);
726 	if (buf == NULL)
727 		return -1;
728 
729 	dmi_table(buf, dmi_len, dmi_num, decode, private_data);
730 
731 	iounmap(buf);
732 	return 0;
733 }
734 EXPORT_SYMBOL_GPL(dmi_walk);
735 
736 /**
737  * dmi_match - compare a string to the dmi field (if exists)
738  * @f: DMI field identifier
739  * @str: string to compare the DMI field to
740  *
741  * Returns true if the requested field equals to the str (including NULL).
742  */
743 bool dmi_match(enum dmi_field f, const char *str)
744 {
745 	const char *info = dmi_get_system_info(f);
746 
747 	if (info == NULL || str == NULL)
748 		return info == str;
749 
750 	return !strcmp(info, str);
751 }
752 EXPORT_SYMBOL_GPL(dmi_match);
753