arch/i386/kernel/bootflag.c

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