/* *	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;}module_init(sbf_init);