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SubjectRe: Linux should not set the "PnP OS" boot flag
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Date
Here's a slightly neater version of the patch which gives control
over the DIAG bit also. We'd need config options for "CONFIG_SBF_DIAG"
and "CONFIG_SBF_PNPOS".

I'd like to say in defense of this patch that the more conservative
thing to do _by default_ is to let the PnP BIOS configure devices
before Linux boots. The cost SFAIK is only time. The cost of leaving
devices unconfigured is, for some people, oopses.

--
Thomas

The patch:
--- linux-2.4.10-ac7/arch/i386/kernel/bootflag.c Fri Oct 5 14:57:10 2001
+++ linux-2.4.10-ac7-fix/arch/i386/kernel/bootflag.c Sun Oct 7 13:45:41 2001
@@ -15,6 +15,13 @@

#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)
+
struct sbf_boot
{
u8 sbf_signature[4];
@@ -59,7 +66,7 @@
return 0;

if (sb.sbf_len == 39)
- printk (KERN_WARNING "ACPI BOOT descriptor is wrong length (%d)\n",
+ printk (KERN_WARNING "SBF: ACPI BOOT descriptor is wrong length (%d)\n",
sb.sbf_len);

sbf_port = sb.sbf_cmos; /* Save CMOS port */
@@ -81,61 +88,65 @@

static void __init sbf_write(u8 v)
{
+ unsigned long flags;
+
if(sbf_port != -1)
{
- v &= ~(1<<7);
+ v &= ~SBF_PARITY;
if(!parity(v))
- v|=1<<7;
+ v|=SBF_PARITY; /* Make parity odd */

- spin_lock(&rtc_lock);
+ printk(KERN_INFO "SBF: Setting boot flags 0x%x\n",v);
+
+ spin_lock_irqsave(&rtc_lock, flags);
CMOS_WRITE(v, sbf_port);
- spin_unlock(&rtc_lock);
+ 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(&rtc_lock);
+ spin_lock_irqsave(&rtc_lock, flags);
v = CMOS_READ(sbf_port);
- spin_unlock(&rtc_lock);
+ spin_unlock_irqrestore(&rtc_lock, flags);
return v;
}

static int __init sbf_value_valid(u8 v)
{
- if(v&0x78) /* Reserved bits */
+ if(v&SBF_RESERVED) /* Reserved bits should be 0 */
return 0;
if(!parity(v))
return 0;
return 1;
}

-
static void __init sbf_bootup(void)
{
u8 v = sbf_read();
if(!sbf_value_valid(v))
- v = 0;
-#if defined(CONFIG_PNPBIOS)
- /* Tell the BIOS to fast init as we are a PnP OS */
- v |= (1<<0); /* Set PNPOS flag */
+ printk(KERN_WARNING "SBF: Simple boot flag value 0x%x read from CMOS RAM was invalid\n",v);
+
+ v &= ~SBF_RESERVED;
+ v &= ~SBF_BOOTING;
+#if defined(CONFIG_SBF_DIAG)
+ v |= SBF_DIAG;
+#else
+ v &= ~SBF_DIAG;
+#endif
+#if defined(CONFIG_SBF_PNPOS)
+ v |= SBF_PNPOS;
+#else
+ v &= ~SBF_PNPOS;
#endif
- sbf_write(v);
-}

-#ifdef NOT_USED
-void linux_booted_ok(void)
-{
- u8 v = sbf_read();
- if(!sbf_value_valid(v))
- return;
- v &= ~(1<<1); /* Clear BOOTING flag */
sbf_write(v);
}
-#endif /* NOT_USED */

static int __init sbf_init(void)
{
@@ -235,7 +246,7 @@
if(sbf_struct_valid(rp))
{
/* Found the BOOT table and processed it */
- printk(KERN_INFO "Simple Boot Flag extension found and enabled.\n");
+ printk(KERN_INFO "SBF: Simple Boot Flag extension found and enabled.\n");
}
iounmap((void *)rp);
}
-
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