[mirror_ubuntu-bionic-kernel.git] / arch / x86 / kernel / bootflag.c

// SPDX-License-Identifier: GPL-2.0
/*
 *	Implement 'Simple Boot Flag Specification 2.0'
 */
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/string.h>
#include <linux/spinlock.h>
#include <linux/acpi.h>
#include <asm/io.h>

#include <linux/mc146818rtc.h>

#define SBF_RESERVED (0x78)
#define SBF_PNPOS    (1<<0)
#define SBF_BOOTING  (1<<1)
#define SBF_DIAG     (1<<2)
#define SBF_PARITY   (1<<7)

int sbf_port __initdata = -1;	/* set via acpi_boot_init() */

static int __init parity(u8 v)
{
	int x = 0;
	int i;

	for (i = 0; i < 8; i++) {
		x ^= (v & 1);
		v >>= 1;
	}

	return x;
}

static void __init sbf_write(u8 v)
{
	unsigned long flags;

	if (sbf_port != -1) {
		v &= ~SBF_PARITY;
		if (!parity(v))
			v |= SBF_PARITY;

		printk(KERN_INFO "Simple Boot Flag at 0x%x set to 0x%x\n",
			sbf_port, v);

		spin_lock_irqsave(&rtc_lock, flags);
		CMOS_WRITE(v, sbf_port);
		spin_unlock_irqrestore(&rtc_lock, flags);
	}
}

static u8 __init sbf_read(void)
{
	unsigned long flags;
	u8 v;

	if (sbf_port == -1)
		return 0;

	spin_lock_irqsave(&rtc_lock, flags);
	v = CMOS_READ(sbf_port);
	spin_unlock_irqrestore(&rtc_lock, flags);

	return v;
}

static int __init sbf_value_valid(u8 v)
{
	if (v & SBF_RESERVED)		/* Reserved bits */
		return 0;
	if (!parity(v))
		return 0;

	return 1;
}

static int __init sbf_init(void)
{
	u8 v;

	if (sbf_port == -1)
		return 0;

	v = sbf_read();
	if (!sbf_value_valid(v)) {
		printk(KERN_WARNING "Simple Boot Flag value 0x%x read from "
			"CMOS RAM was invalid\n", v);
	}

	v &= ~SBF_RESERVED;
	v &= ~SBF_BOOTING;
	v &= ~SBF_DIAG;
#if defined(CONFIG_ISAPNP)
	v |= SBF_PNPOS;
#endif
	sbf_write(v);

	return 0;
}
arch_initcall(sbf_init);
Commit	Line	Data
b2441318	1	// SPDX-License-Identifier: GPL-2.0
1da177e4 LT	2	/*
	3	* Implement 'Simple Boot Flag Specification 2.0'
	4	*/
1da177e4 LT	5	#include <linux/types.h>
	6	#include <linux/kernel.h>
	7	#include <linux/init.h>
	8	#include <linux/string.h>
1da177e4 LT	9	#include <linux/spinlock.h>
	10	#include <linux/acpi.h>
	11	#include <asm/io.h>
	12
	13	#include <linux/mc146818rtc.h>
	14
1da177e4 LT	15	#define SBF_RESERVED (0x78)
	16	#define SBF_PNPOS (1<<0)
	17	#define SBF_BOOTING (1<<1)
	18	#define SBF_DIAG (1<<2)
	19	#define SBF_PARITY (1<<7)
	20
1da177e4 LT	21	int sbf_port __initdata = -1; /* set via acpi_boot_init() */
1da177e4 LT	22
1da177e4 LT	23	static int __init parity(u8 v)
	24	{
	25	int x = 0;
	26	int i;
8eed9260 CG	27
	28	for (i = 0; i < 8; i++) {
	29	x ^= (v & 1);
	30	v >>= 1;
1da177e4	31	}
8eed9260	32
1da177e4 LT	33	return x;
	34	}
	35
	36	static void __init sbf_write(u8 v)
	37	{
	38	unsigned long flags;
8eed9260 CG	39
8eed9260 CG	40	if (sbf_port != -1) {
1da177e4	41	v &= ~SBF_PARITY;
8eed9260 CG	42	if (!parity(v))
8eed9260 CG	43	v \|= SBF_PARITY;
1da177e4	44
8eed9260 CG	45	printk(KERN_INFO "Simple Boot Flag at 0x%x set to 0x%x\n",
8eed9260 CG	46	sbf_port, v);
1da177e4 LT	47
	48	spin_lock_irqsave(&rtc_lock, flags);
	49	CMOS_WRITE(v, sbf_port);
	50	spin_unlock_irqrestore(&rtc_lock, flags);
	51	}
	52	}
	53
	54	static u8 __init sbf_read(void)
	55	{
1da177e4	56	unsigned long flags;
8eed9260 CG	57	u8 v;
	58
	59	if (sbf_port == -1)
1da177e4	60	return 0;
8eed9260	61
1da177e4 LT	62	spin_lock_irqsave(&rtc_lock, flags);
	63	v = CMOS_READ(sbf_port);
	64	spin_unlock_irqrestore(&rtc_lock, flags);
8eed9260	65
1da177e4 LT	66	return v;
	67	}
	68
	69	static int __init sbf_value_valid(u8 v)
	70	{
8eed9260	71	if (v & SBF_RESERVED) /* Reserved bits */
1da177e4	72	return 0;
8eed9260	73	if (!parity(v))
1da177e4	74	return 0;
8eed9260	75
1da177e4 LT	76	return 1;
	77	}
	78
	79	static int __init sbf_init(void)
	80	{
	81	u8 v;
8eed9260 CG	82
8eed9260 CG	83	if (sbf_port == -1)
1da177e4	84	return 0;
8eed9260	85
1da177e4	86	v = sbf_read();
8eed9260 CG	87	if (!sbf_value_valid(v)) {
	88	printk(KERN_WARNING "Simple Boot Flag value 0x%x read from "
	89	"CMOS RAM was invalid\n", v);
	90	}
1da177e4 LT	91
	92	v &= ~SBF_RESERVED;
	93	v &= ~SBF_BOOTING;
	94	v &= ~SBF_DIAG;
	95	#if defined(CONFIG_ISAPNP)
	96	v \|= SBF_PNPOS;
	97	#endif
	98	sbf_write(v);
8eed9260	99
1da177e4 LT	100	return 0;
1da177e4 LT	101	}
1206f535	102	arch_initcall(sbf_init);