aboutsummaryrefslogtreecommitdiffstats
path: root/drivers/acpi/acpica/hwregs.c
blob: e0fd9b4978cd6a22af964a3165d26cfd62ea032f (plain) (blame)
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
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
/*******************************************************************************
 *
 * Module Name: hwregs - Read/write access functions for the various ACPI
 *                       control and status registers.
 *
 ******************************************************************************/

/*
 * Copyright (C) 2000 - 2014, Intel Corp.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions, and the following disclaimer,
 *    without modification.
 * 2. Redistributions in binary form must reproduce at minimum a disclaimer
 *    substantially similar to the "NO WARRANTY" disclaimer below
 *    ("Disclaimer") and any redistribution must be conditioned upon
 *    including a substantially similar Disclaimer requirement for further
 *    binary redistribution.
 * 3. Neither the names of the above-listed copyright holders nor the names
 *    of any contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * Alternatively, this software may be distributed under the terms of the
 * GNU General Public License ("GPL") version 2 as published by the Free
 * Software Foundation.
 *
 * NO WARRANTY
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGES.
 */

#include <acpi/acpi.h>
#include "accommon.h"
#include "acevents.h"

#define _COMPONENT          ACPI_HARDWARE
ACPI_MODULE_NAME("hwregs")

#if (!ACPI_REDUCED_HARDWARE)
/* Local Prototypes */
static acpi_status
acpi_hw_read_multiple(u32 *value,
		      struct acpi_generic_address *register_a,
		      struct acpi_generic_address *register_b);

static acpi_status
acpi_hw_write_multiple(u32 value,
		       struct acpi_generic_address *register_a,
		       struct acpi_generic_address *register_b);

#endif				/* !ACPI_REDUCED_HARDWARE */

/******************************************************************************
 *
 * FUNCTION:    acpi_hw_validate_register
 *
 * PARAMETERS:  reg                 - GAS register structure
 *              max_bit_width       - Max bit_width supported (32 or 64)
 *              address             - Pointer to where the gas->address
 *                                    is returned
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Validate the contents of a GAS register. Checks the GAS
 *              pointer, Address, space_id, bit_width, and bit_offset.
 *
 ******************************************************************************/

acpi_status
acpi_hw_validate_register(struct acpi_generic_address *reg,
			  u8 max_bit_width, u64 *address)
{

	/* Must have a valid pointer to a GAS structure */

	if (!reg) {
		return (AE_BAD_PARAMETER);
	}

	/*
	 * Copy the target address. This handles possible alignment issues.
	 * Address must not be null. A null address also indicates an optional
	 * ACPI register that is not supported, so no error message.
	 */
	ACPI_MOVE_64_TO_64(address, &reg->address);
	if (!(*address)) {
		return (AE_BAD_ADDRESS);
	}

	/* Validate the space_ID */

	if ((reg->space_id != ACPI_ADR_SPACE_SYSTEM_MEMORY) &&
	    (reg->space_id != ACPI_ADR_SPACE_SYSTEM_IO)) {
		ACPI_ERROR((AE_INFO,
			    "Unsupported address space: 0x%X", reg->space_id));
		return (AE_SUPPORT);
	}

	/* Validate the bit_width */

	if ((reg->bit_width != 8) &&
	    (reg->bit_width != 16) &&
	    (reg->bit_width != 32) && (reg->bit_width != max_bit_width)) {
		ACPI_ERROR((AE_INFO,
			    "Unsupported register bit width: 0x%X",
			    reg->bit_width));
		return (AE_SUPPORT);
	}

	/* Validate the bit_offset. Just a warning for now. */

	if (reg->bit_offset != 0) {
		ACPI_WARNING((AE_INFO,
			      "Unsupported register bit offset: 0x%X",
			      reg->bit_offset));
	}

	return (AE_OK);
}

/******************************************************************************
 *
 * FUNCTION:    acpi_hw_read
 *
 * PARAMETERS:  value               - Where the value is returned
 *              reg                 - GAS register structure
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Read from either memory or IO space. This is a 32-bit max
 *              version of acpi_read, used internally since the overhead of
 *              64-bit values is not needed.
 *
 * LIMITATIONS: <These limitations also apply to acpi_hw_write>
 *      bit_width must be exactly 8, 16, or 32.
 *      space_ID must be system_memory or system_IO.
 *      bit_offset and access_width are currently ignored, as there has
 *          not been a need to implement these.
 *
 ******************************************************************************/

acpi_status acpi_hw_read(u32 *value, struct acpi_generic_address *reg)
{
	u64 address;
	u64 value64;
	acpi_status status;

	ACPI_FUNCTION_NAME(hw_read);

	/* Validate contents of the GAS register */

	status = acpi_hw_validate_register(reg, 32, &address);
	if (ACPI_FAILURE(status)) {
		return (status);
	}

	/* Initialize entire 32-bit return value to zero */

	*value = 0;

	/*
	 * Two address spaces supported: Memory or IO. PCI_Config is
	 * not supported here because the GAS structure is insufficient
	 */
	if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) {
		status = acpi_os_read_memory((acpi_physical_address)
					     address, &value64, reg->bit_width);

		*value = (u32)value64;
	} else {		/* ACPI_ADR_SPACE_SYSTEM_IO, validated earlier */

		status = acpi_hw_read_port((acpi_io_address)
					   address, value, reg->bit_width);
	}

	ACPI_DEBUG_PRINT((ACPI_DB_IO,
			  "Read:  %8.8X width %2d from %8.8X%8.8X (%s)\n",
			  *value, reg->bit_width, ACPI_FORMAT_UINT64(address),
			  acpi_ut_get_region_name(reg->space_id)));

	return (status);
}

/******************************************************************************
 *
 * FUNCTION:    acpi_hw_write
 *
 * PARAMETERS:  value               - Value to be written
 *              reg                 - GAS register structure
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Write to either memory or IO space. This is a 32-bit max
 *              version of acpi_write, used internally since the overhead of
 *              64-bit values is not needed.
 *
 ******************************************************************************/

acpi_status acpi_hw_write(u32 value, struct acpi_generic_address *reg)
{
	u64 address;
	acpi_status status;

	ACPI_FUNCTION_NAME(hw_write);

	/* Validate contents of the GAS register */

	status = acpi_hw_validate_register(reg, 32, &address);
	if (ACPI_FAILURE(status)) {
		return (status);
	}

	/*
	 * Two address spaces supported: Memory or IO. PCI_Config is
	 * not supported here because the GAS structure is insufficient
	 */
	if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) {
		status = acpi_os_write_memory((acpi_physical_address)
					      address, (u64)value,
					      reg->bit_width);
	} else {		/* ACPI_ADR_SPACE_SYSTEM_IO, validated earlier */

		status = acpi_hw_write_port((acpi_io_address)
					    address, value, reg->bit_width);
	}

	ACPI_DEBUG_PRINT((ACPI_DB_IO,
			  "Wrote: %8.8X width %2d   to %8.8X%8.8X (%s)\n",
			  value, reg->bit_width, ACPI_FORMAT_UINT64(address),
			  acpi_ut_get_region_name(reg->space_id)));

	return (status);
}

#if (!ACPI_REDUCED_HARDWARE)
/*******************************************************************************
 *
 * FUNCTION:    acpi_hw_clear_acpi_status
 *
 * PARAMETERS:  None
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Clears all fixed and general purpose status bits
 *
 ******************************************************************************/

acpi_status acpi_hw_clear_acpi_status(void)
{
	acpi_status status;
	acpi_cpu_flags lock_flags = 0;

	ACPI_FUNCTION_TRACE(hw_clear_acpi_status);

	ACPI_DEBUG_PRINT((ACPI_DB_IO, "About to write %04X to %8.8X%8.8X\n",
			  ACPI_BITMASK_ALL_FIXED_STATUS,
			  ACPI_FORMAT_UINT64(acpi_gbl_xpm1a_status.address)));

	lock_flags = acpi_os_acquire_lock(acpi_gbl_hardware_lock);

	/* Clear the fixed events in PM1 A/B */

	status = acpi_hw_register_write(ACPI_REGISTER_PM1_STATUS,
					ACPI_BITMASK_ALL_FIXED_STATUS);

	acpi_os_release_lock(acpi_gbl_hardware_lock, lock_flags);

	if (ACPI_FAILURE(status))
		goto exit;

	/* Clear the GPE Bits in all GPE registers in all GPE blocks */

	status = acpi_ev_walk_gpe_list(acpi_hw_clear_gpe_block, NULL);

exit:
	return_ACPI_STATUS(status);
}

/*******************************************************************************
 *
 * FUNCTION:    acpi_hw_get_bit_register_info
 *
 * PARAMETERS:  register_id         - Index of ACPI Register to access
 *
 * RETURN:      The bitmask to be used when accessing the register
 *
 * DESCRIPTION: Map register_id into a register bitmask.
 *
 ******************************************************************************/

struct acpi_bit_register_info *acpi_hw_get_bit_register_info(u32 register_id)
{
	ACPI_FUNCTION_ENTRY();

	if (register_id > ACPI_BITREG_MAX) {
		ACPI_ERROR((AE_INFO, "Invalid BitRegister ID: 0x%X",
			    register_id));
		return (NULL);
	}

	return (&acpi_gbl_bit_register_info[register_id]);
}

/******************************************************************************
 *
 * FUNCTION:    acpi_hw_write_pm1_control
 *
 * PARAMETERS:  pm1a_control        - Value to be written to PM1A control
 *              pm1b_control        - Value to be written to PM1B control
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Write the PM1 A/B control registers. These registers are
 *              different than than the PM1 A/B status and enable registers
 *              in that different values can be written to the A/B registers.
 *              Most notably, the SLP_TYP bits can be different, as per the
 *              values returned from the _Sx predefined methods.
 *
 ******************************************************************************/

acpi_status acpi_hw_write_pm1_control(u32 pm1a_control, u32 pm1b_control)
{
	acpi_status status;

	ACPI_FUNCTION_TRACE(hw_write_pm1_control);

	status =
	    acpi_hw_write(pm1a_control, &acpi_gbl_FADT.xpm1a_control_block);
	if (ACPI_FAILURE(status)) {
		return_ACPI_STATUS(status);
	}

	if (acpi_gbl_FADT.xpm1b_control_block.address) {
		status =
		    acpi_hw_write(pm1b_control,
				  &acpi_gbl_FADT.xpm1b_control_block);
	}
	return_ACPI_STATUS(status);
}

/******************************************************************************
 *
 * FUNCTION:    acpi_hw_register_read
 *
 * PARAMETERS:  register_id         - ACPI Register ID
 *              return_value        - Where the register value is returned
 *
 * RETURN:      Status and the value read.
 *
 * DESCRIPTION: Read from the specified ACPI register
 *
 ******************************************************************************/
acpi_status acpi_hw_register_read(u32 register_id, u32 *return_value)
{
	u32 value = 0;
	acpi_status status;

	ACPI_FUNCTION_TRACE(hw_register_read);

	switch (register_id) {
	case ACPI_REGISTER_PM1_STATUS:	/* PM1 A/B: 16-bit access each */

		status = acpi_hw_read_multiple(&value,
					       &acpi_gbl_xpm1a_status,
					       &acpi_gbl_xpm1b_status);
		break;

	case ACPI_REGISTER_PM1_ENABLE:	/* PM1 A/B: 16-bit access each */

		status = acpi_hw_read_multiple(&value,
					       &acpi_gbl_xpm1a_enable,
					       &acpi_gbl_xpm1b_enable);
		break;

	case ACPI_REGISTER_PM1_CONTROL:	/* PM1 A/B: 16-bit access each */

		status = acpi_hw_read_multiple(&value,
					       &acpi_gbl_FADT.
					       xpm1a_control_block,
					       &acpi_gbl_FADT.
					       xpm1b_control_block);

		/*
		 * Zero the write-only bits. From the ACPI specification, "Hardware
		 * Write-Only Bits": "Upon reads to registers with write-only bits,
		 * software masks out all write-only bits."
		 */
		value &= ~ACPI_PM1_CONTROL_WRITEONLY_BITS;
		break;

	case ACPI_REGISTER_PM2_CONTROL:	/* 8-bit access */

		status =
		    acpi_hw_read(&value, &acpi_gbl_FADT.xpm2_control_block);
		break;

	case ACPI_REGISTER_PM_TIMER:	/* 32-bit access */

		status = acpi_hw_read(&value, &acpi_gbl_FADT.xpm_timer_block);
		break;

	case ACPI_REGISTER_SMI_COMMAND_BLOCK:	/* 8-bit access */

		status =
		    acpi_hw_read_port(acpi_gbl_FADT.smi_command, &value, 8);
		break;

	default:

		ACPI_ERROR((AE_INFO, "Unknown Register ID: 0x%X", register_id));
		status = AE_BAD_PARAMETER;
		break;
	}

	if (ACPI_SUCCESS(status)) {
		*return_value = value;
	}

	return_ACPI_STATUS(status);
}

/******************************************************************************
 *
 * FUNCTION:    acpi_hw_register_write
 *
 * PARAMETERS:  register_id         - ACPI Register ID
 *              value               - The value to write
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Write to the specified ACPI register
 *
 * NOTE: In accordance with the ACPI specification, this function automatically
 * preserves the value of the following bits, meaning that these bits cannot be
 * changed via this interface:
 *
 * PM1_CONTROL[0] = SCI_EN
 * PM1_CONTROL[9]
 * PM1_STATUS[11]
 *
 * ACPI References:
 * 1) Hardware Ignored Bits: When software writes to a register with ignored
 *      bit fields, it preserves the ignored bit fields
 * 2) SCI_EN: OSPM always preserves this bit position
 *
 ******************************************************************************/

acpi_status acpi_hw_register_write(u32 register_id, u32 value)
{
	acpi_status status;
	u32 read_value;

	ACPI_FUNCTION_TRACE(hw_register_write);

	switch (register_id) {
	case ACPI_REGISTER_PM1_STATUS:	/* PM1 A/B: 16-bit access each */
		/*
		 * Handle the "ignored" bit in PM1 Status. According to the ACPI
		 * specification, ignored bits are to be preserved when writing.
		 * Normally, this would mean a read/modify/write sequence. However,
		 * preserving a bit in the status register is different. Writing a
		 * one clears the status, and writing a zero preserves the status.
		 * Therefore, we must always write zero to the ignored bit.
		 *
		 * This behavior is clarified in the ACPI 4.0 specification.
		 */
		value &= ~ACPI_PM1_STATUS_PRESERVED_BITS;

		status = acpi_hw_write_multiple(value,
						&acpi_gbl_xpm1a_status,
						&acpi_gbl_xpm1b_status);
		break;

	case ACPI_REGISTER_PM1_ENABLE:	/* PM1 A/B: 16-bit access each */

		status = acpi_hw_write_multiple(value,
						&acpi_gbl_xpm1a_enable,
						&acpi_gbl_xpm1b_enable);
		break;

	case ACPI_REGISTER_PM1_CONTROL:	/* PM1 A/B: 16-bit access each */
		/*
		 * Perform a read first to preserve certain bits (per ACPI spec)
		 * Note: This includes SCI_EN, we never want to change this bit
		 */
		status = acpi_hw_read_multiple(&read_value,
					       &acpi_gbl_FADT.
					       xpm1a_control_block,
					       &acpi_gbl_FADT.
					       xpm1b_control_block);
		if (ACPI_FAILURE(status)) {
			goto exit;
		}

		/* Insert the bits to be preserved */

		ACPI_INSERT_BITS(value, ACPI_PM1_CONTROL_PRESERVED_BITS,
				 read_value);

		/* Now we can write the data */

		status = acpi_hw_write_multiple(value,
						&acpi_gbl_FADT.
						xpm1a_control_block,
						&acpi_gbl_FADT.
						xpm1b_control_block);
		break;

	case ACPI_REGISTER_PM2_CONTROL:	/* 8-bit access */
		/*
		 * For control registers, all reserved bits must be preserved,
		 * as per the ACPI spec.
		 */
		status =
		    acpi_hw_read(&read_value,
				 &acpi_gbl_FADT.xpm2_control_block);
		if (ACPI_FAILURE(status)) {
			goto exit;
		}

		/* Insert the bits to be preserved */

		ACPI_INSERT_BITS(value, ACPI_PM2_CONTROL_PRESERVED_BITS,
				 read_value);

		status =
		    acpi_hw_write(value, &acpi_gbl_FADT.xpm2_control_block);
		break;

	case ACPI_REGISTER_PM_TIMER:	/* 32-bit access */

		status = acpi_hw_write(value, &acpi_gbl_FADT.xpm_timer_block);
		break;

	case ACPI_REGISTER_SMI_COMMAND_BLOCK:	/* 8-bit access */

		/* SMI_CMD is currently always in IO space */

		status =
		    acpi_hw_write_port(acpi_gbl_FADT.smi_command, value, 8);
		break;

	default:

		ACPI_ERROR((AE_INFO, "Unknown Register ID: 0x%X", register_id));
		status = AE_BAD_PARAMETER;
		break;
	}

exit:
	return_ACPI_STATUS(status);
}

/******************************************************************************
 *
 * FUNCTION:    acpi_hw_read_multiple
 *
 * PARAMETERS:  value               - Where the register value is returned
 *              register_a           - First ACPI register (required)
 *              register_b           - Second ACPI register (optional)
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Read from the specified two-part ACPI register (such as PM1 A/B)
 *
 ******************************************************************************/

static acpi_status
acpi_hw_read_multiple(u32 *value,
		      struct acpi_generic_address *register_a,
		      struct acpi_generic_address *register_b)
{
	u32 value_a = 0;
	u32 value_b = 0;
	acpi_status status;

	/* The first register is always required */

	status = acpi_hw_read(&value_a, register_a);
	if (ACPI_FAILURE(status)) {
		return (status);
	}

	/* Second register is optional */

	if (register_b->address) {
		status = acpi_hw_read(&value_b, register_b);
		if (ACPI_FAILURE(status)) {
			return (status);
		}
	}

	/*
	 * OR the two return values together. No shifting or masking is necessary,
	 * because of how the PM1 registers are defined in the ACPI specification:
	 *
	 * "Although the bits can be split between the two register blocks (each
	 * register block has a unique pointer within the FADT), the bit positions
	 * are maintained. The register block with unimplemented bits (that is,
	 * those implemented in the other register block) always returns zeros,
	 * and writes have no side effects"
	 */
	*value = (value_a | value_b);
	return (AE_OK);
}

/******************************************************************************
 *
 * FUNCTION:    acpi_hw_write_multiple
 *
 * PARAMETERS:  value               - The value to write
 *              register_a           - First ACPI register (required)
 *              register_b           - Second ACPI register (optional)
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Write to the specified two-part ACPI register (such as PM1 A/B)
 *
 ******************************************************************************/

static acpi_status
acpi_hw_write_multiple(u32 value,
		       struct acpi_generic_address *register_a,
		       struct acpi_generic_address *register_b)
{
	acpi_status status;

	/* The first register is always required */

	status = acpi_hw_write(value, register_a);
	if (ACPI_FAILURE(status)) {
		return (status);
	}

	/*
	 * Second register is optional
	 *
	 * No bit shifting or clearing is necessary, because of how the PM1
	 * registers are defined in the ACPI specification:
	 *
	 * "Although the bits can be split between the two register blocks (each
	 * register block has a unique pointer within the FADT), the bit positions
	 * are maintained. The register block with unimplemented bits (that is,
	 * those implemented in the other register block) always returns zeros,
	 * and writes have no side effects"
	 */
	if (register_b->address) {
		status = acpi_hw_write(value, register_b);
	}

	return (status);
}

#endif				/* !ACPI_REDUCED_HARDWARE */