Better tests for CM#1 and CM#2syslinux-3.10-pre6

1 files changed, 56 insertions, 33 deletions

diff --git a/com32/lib/pci/cfgtype.c b/com32/lib/pci/cfgtype.c
index 0fdc81e7..0f8c623f 100644
--- a/com32/lib/pci/cfgtype.c
+++ b/com32/lib/pci/cfgtype.c
@@ -4,6 +4,52 @@
 
 enum pci_config_type __pci_cfg_type;
 
+static int type1_ok(void)
+{
+  uint32_t oldcf8, newcf8;
+
+  /* Test for Configuration Method #1 */
+
+  /* Note: XFree86 writes ~0 and expects to read back 0x80fffffc.  Linux
+     does this less severe test; go with Linux. */
+
+  cli();
+  outb(1, 0xcfb);		/* For old Intel chipsets */
+  oldcf8 = inl(0xcf8);
+  outl(0x80000000, 0xcf8);
+  newcf8 = inl(0xcf8);
+  outl(oldcf8, 0xcf8);
+  sti();
+
+  return newcf8 == 0x80000000;
+}
+
+static int type2_ok(void)
+{
+  uint8_t oldcf8, oldcfa;
+  uint8_t cf8, cfa;
+
+  /* Test for Configuration Method #2 */
+
+  /* CM#2 is hard to probe for, but let's do our best... */
+
+  cli();
+  outb(0, 0xcfb);		/* For old Intel chipsets */
+  oldcf8 = inb(0xcf8);
+  outb(0, 0xcf8);
+  oldcfa = inb(0xcfa);
+  outb(0, 0xcfa);
+  
+  cf8 = inb(0xcf8);
+  cfa = inb(0xcfa);
+  
+  outb(oldcf8, 0xcf8);
+  outb(oldcfa, 0xcfa);
+  sti();
+  
+  return cf8 == 0 && cfa == 0;
+}
+
 int pci_set_config_type(enum pci_config_type type)
 {
   static const com32sys_t ireg = {
@@ -22,43 +68,20 @@ int pci_set_config_type(enum pci_config_type type)
     if ( !(oreg.eflags.l & EFLAGS_CF) &&
 	 oreg.eax.b[1] == 0 && oreg.edx.l == 0x20494250 ) {
       /* PCI BIOS present.  Use direct access if we know how to do it. */
-      if ( oreg.eax.b[0] & 1 )
+
+      if ( (oreg.eax.b[0] & 1) && type1_ok() )
 	type = PCI_CFG_TYPE1;
-      else if ( oreg.eax.b[0] & 2 )
+      else if ( (oreg.eax.b[0] & 2) && type2_ok() )
 	type = PCI_CFG_TYPE2;
       else
-	type = PCI_CFG_BIOS;
+	type = PCI_CFG_BIOS;	/* Use BIOS calls as fallback */
+
+    } else if ( type1_ok() ) {
+      type = PCI_CFG_TYPE1;
+    } else if ( type2_ok() ) {
+      type = PCI_CFG_TYPE2;
     } else {
-      /* Try to detect CM #1 */
-      uint32_t oldcf8, newcf8;
-      
-      cli();
-      outb(1, 0xcfb);		/* Linux does this for some reason? */
-      oldcf8 = inl(0xcf8);
-      outl(0x80000000, 0xcf8);
-      newcf8 = inl(0xcf8);
-      outl(oldcf8, 0xcf8);
-      sti();
-
-      if ( newcf8 == 0x80000000 )
-	type = PCI_CFG_TYPE1;
-      else {
-	uint8_t oldcf8, oldcfa;
-	/* Try to detect CM#2 */
-	cli();
-	outb(0, 0xcfb);		/* Linux does this for some reason? */
-	oldcf8 = inb(0xcf8);
-	outb(0, 0xcf8);
-	oldcfa = inb(0xcfa);
-	outb(0, 0xcfa);
-	
-	if ( inb(0xcf8) == 0 && inb(0xcfa) == 0 )
-	  type = PCI_CFG_TYPE2;
-
-	outb(oldcf8, 0xcf8);
-	outb(oldcfa, 0xcfa);
-	sti();
-      }
+      type = PCI_CFG_NONE;	/* Badness... */
     }
   }