PageRenderTime 29ms CodeModel.GetById 17ms app.highlight 8ms RepoModel.GetById 2ms app.codeStats 0ms

/arch/x86/kernel/bootflag.c

https://gitlab.com/Team-OSE-old/SimpleKernel
C | 101 lines | 77 code | 21 blank | 3 comment | 11 complexity | afb573cf63c3ab79823af8b0651e76b4 MD5 | raw file
  1/*
  2 *	Implement 'Simple Boot Flag Specification 2.0'
  3 */
  4#include <linux/types.h>
  5#include <linux/kernel.h>
  6#include <linux/init.h>
  7#include <linux/string.h>
  8#include <linux/spinlock.h>
  9#include <linux/acpi.h>
 10#include <asm/io.h>
 11
 12#include <linux/mc146818rtc.h>
 13
 14#define SBF_RESERVED (0x78)
 15#define SBF_PNPOS    (1<<0)
 16#define SBF_BOOTING  (1<<1)
 17#define SBF_DIAG     (1<<2)
 18#define SBF_PARITY   (1<<7)
 19
 20int sbf_port __initdata = -1;	/* set via acpi_boot_init() */
 21
 22static int __init parity(u8 v)
 23{
 24	int x = 0;
 25	int i;
 26
 27	for (i = 0; i < 8; i++) {
 28		x ^= (v & 1);
 29		v >>= 1;
 30	}
 31
 32	return x;
 33}
 34
 35static void __init sbf_write(u8 v)
 36{
 37	unsigned long flags;
 38
 39	if (sbf_port != -1) {
 40		v &= ~SBF_PARITY;
 41		if (!parity(v))
 42			v |= SBF_PARITY;
 43
 44		printk(KERN_INFO "Simple Boot Flag at 0x%x set to 0x%x\n",
 45			sbf_port, v);
 46
 47		spin_lock_irqsave(&rtc_lock, flags);
 48		CMOS_WRITE(v, sbf_port);
 49		spin_unlock_irqrestore(&rtc_lock, flags);
 50	}
 51}
 52
 53static u8 __init sbf_read(void)
 54{
 55	unsigned long flags;
 56	u8 v;
 57
 58	if (sbf_port == -1)
 59		return 0;
 60
 61	spin_lock_irqsave(&rtc_lock, flags);
 62	v = CMOS_READ(sbf_port);
 63	spin_unlock_irqrestore(&rtc_lock, flags);
 64
 65	return v;
 66}
 67
 68static int __init sbf_value_valid(u8 v)
 69{
 70	if (v & SBF_RESERVED)		/* Reserved bits */
 71		return 0;
 72	if (!parity(v))
 73		return 0;
 74
 75	return 1;
 76}
 77
 78static int __init sbf_init(void)
 79{
 80	u8 v;
 81
 82	if (sbf_port == -1)
 83		return 0;
 84
 85	v = sbf_read();
 86	if (!sbf_value_valid(v)) {
 87		printk(KERN_WARNING "Simple Boot Flag value 0x%x read from "
 88			"CMOS RAM was invalid\n", v);
 89	}
 90
 91	v &= ~SBF_RESERVED;
 92	v &= ~SBF_BOOTING;
 93	v &= ~SBF_DIAG;
 94#if defined(CONFIG_ISAPNP)
 95	v |= SBF_PNPOS;
 96#endif
 97	sbf_write(v);
 98
 99	return 0;
100}
101module_init(sbf_init);