100 lines
1.6 KiB
C
100 lines
1.6 KiB
C
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/*
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* Implement 'Simple Boot Flag Specification 2.0'
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*/
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#include <linux/config.h>
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#include <linux/types.h>
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#include <linux/kernel.h>
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#include <linux/init.h>
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#include <linux/string.h>
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#include <linux/slab.h>
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#include <linux/spinlock.h>
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#include <linux/acpi.h>
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#include <asm/io.h>
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#include <linux/mc146818rtc.h>
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#define SBF_RESERVED (0x78)
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#define SBF_PNPOS (1<<0)
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#define SBF_BOOTING (1<<1)
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#define SBF_DIAG (1<<2)
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#define SBF_PARITY (1<<7)
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int sbf_port __initdata = -1; /* set via acpi_boot_init() */
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static int __init parity(u8 v)
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{
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int x = 0;
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int i;
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for(i=0;i<8;i++)
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{
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x^=(v&1);
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v>>=1;
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}
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return x;
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}
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static void __init sbf_write(u8 v)
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{
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unsigned long flags;
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if(sbf_port != -1)
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{
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v &= ~SBF_PARITY;
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if(!parity(v))
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v|=SBF_PARITY;
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printk(KERN_INFO "Simple Boot Flag at 0x%x set to 0x%x\n", sbf_port, v);
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spin_lock_irqsave(&rtc_lock, flags);
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CMOS_WRITE(v, sbf_port);
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spin_unlock_irqrestore(&rtc_lock, flags);
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}
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}
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static u8 __init sbf_read(void)
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{
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u8 v;
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unsigned long flags;
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if(sbf_port == -1)
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return 0;
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spin_lock_irqsave(&rtc_lock, flags);
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v = CMOS_READ(sbf_port);
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spin_unlock_irqrestore(&rtc_lock, flags);
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return v;
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}
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static int __init sbf_value_valid(u8 v)
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{
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if(v&SBF_RESERVED) /* Reserved bits */
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return 0;
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if(!parity(v))
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return 0;
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return 1;
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}
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static int __init sbf_init(void)
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{
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u8 v;
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if(sbf_port == -1)
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return 0;
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v = sbf_read();
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if(!sbf_value_valid(v))
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printk(KERN_WARNING "Simple Boot Flag value 0x%x read from CMOS RAM was invalid\n",v);
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v &= ~SBF_RESERVED;
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v &= ~SBF_BOOTING;
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v &= ~SBF_DIAG;
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#if defined(CONFIG_ISAPNP)
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v |= SBF_PNPOS;
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#endif
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sbf_write(v);
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return 0;
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}
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module_init(sbf_init);
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