[PATCH] Ensure boot CD can be accessed

[Christian Franke]

Detecting BIOS CD device by INT13 "Check Extensions" (AH=42) call does 
not work for all BIOSes.

This patch fixes this to allow access to the boot CD.

See also thread "[PATCH] Create floppy emulation boot CD with 
grub-mkimage". The "(cd0" patch from Bean is not included here but 
should also be applied.

Christian

2008-02-10  Christian Franke  <address@hidden>

        * disk/i386/pc/biosdisk.c: Include <grub/machine/kernel.h>.
        (GRUB_MOD_INIT): Make boot CD accessible even if BIOS does not report
        INT13 Extensions for grub_boot_drive.
        * include/grub/i386/pc/biosdisk.h (GRUB_BIOSDISK_MACHINE_CDROM_START):
        Change from 0xe0 to 0x9f to cover more BIOS variants.
        * include/grub/i386/pc/kernel.h (grub_boot_drive): Add EXPORT_VAR.


diff -rup --exclude CVS grub2.orig/disk/i386/pc/biosdisk.c 
grub2/disk/i386/pc/biosdisk.c
--- grub2.orig/disk/i386/pc/biosdisk.c  2008-02-03 20:29:51.500000000 +0100
+++ grub2/disk/i386/pc/biosdisk.c       2008-02-10 12:26:25.843750000 +0100
@@ -18,6 +18,7 @@
 
 #include <grub/machine/biosdisk.h>
 #include <grub/machine/memory.h>
+#include <grub/machine/kernel.h>
 #include <grub/disk.h>
 #include <grub/dl.h>
 #include <grub/mm.h>
@@ -391,6 +392,16 @@ GRUB_MOD_INIT(biosdisk)
        }
     }
 
+  /* Some BIOSes do not report INT13 Extensions for the
+     boot CD.  Ensure that the boot CD can be accessed.  */
+  if (! found
+      && GRUB_BIOSDISK_MACHINE_CDROM_START <= grub_boot_drive
+      && grub_boot_drive < GRUB_BIOSDISK_MACHINE_CDROM_END)
+    {
+      cd_start = grub_boot_drive;
+      found = 1;
+    }
+
   cd_count = found;
 }
 
diff -rup --exclude CVS grub2.orig/include/grub/i386/pc/biosdisk.h 
grub2/include/grub/i386/pc/biosdisk.h
--- grub2.orig/include/grub/i386/pc/biosdisk.h  2008-02-03 20:29:52.187500000 
+0100
+++ grub2/include/grub/i386/pc/biosdisk.h       2008-02-09 15:55:04.713289500 
+0100
@@ -25,7 +25,7 @@
 #define GRUB_BIOSDISK_FLAG_LBA 1
 #define GRUB_BIOSDISK_FLAG_CDROM 2
 
-#define GRUB_BIOSDISK_MACHINE_CDROM_START      0xe0
+#define GRUB_BIOSDISK_MACHINE_CDROM_START      0x9f
 #define GRUB_BIOSDISK_MACHINE_CDROM_END                0xf0
 
 struct grub_biosdisk_data
diff -rup --exclude CVS grub2.orig/include/grub/i386/pc/kernel.h 
grub2/include/grub/i386/pc/kernel.h
--- grub2.orig/include/grub/i386/pc/kernel.h    2008-02-03 20:29:52.375000000 
+0100
+++ grub2/include/grub/i386/pc/kernel.h 2008-02-10 00:16:43.812500000 +0100
@@ -71,7 +71,7 @@ extern grub_int32_t grub_memdisk_image_s
 extern char grub_prefix[];
 
 /* The boot BIOS drive number.  */
-extern grub_int32_t grub_boot_drive;
+extern grub_int32_t EXPORT_VAR(grub_boot_drive);
 
 /* The root BIOS drive number.  */
 extern grub_int32_t grub_root_drive;