diff options
Diffstat (limited to 'arch/x86/kernel/bootflag.c')
-rw-r--r-- | arch/x86/kernel/bootflag.c | 98 |
1 files changed, 98 insertions, 0 deletions
diff --git a/arch/x86/kernel/bootflag.c b/arch/x86/kernel/bootflag.c new file mode 100644 index 0000000..0b98605 --- /dev/null +++ b/arch/x86/kernel/bootflag.c @@ -0,0 +1,98 @@ +/* + * 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/slab.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) +{ + u8 v; + unsigned long flags; + 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); |