arch/x86/kernel/bootflag.c

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