mkdiskimage: support more than 1024 cylinders

If the user wants to generate a disk image with more than 1024
cylinders, print a warning but do the right thing, including labelling
the partitions as LBA partitions.

1 files changed, 22 insertions, 7 deletions

diff --git a/mkdiskimage.in b/mkdiskimage.in
index e772588a..1d66dd49 100755
--- a/mkdiskimage.in
+++ b/mkdiskimage.in
@@ -122,8 +122,7 @@ if ( $c == 0 && $file ne '' ) {
     $c = $len/($h*$s);
 }
 
-if ( $file eq '' || $c < 1 || $c > 1024 ||
-     $h < 1 || $h > 256 || $s < 1 || $s > 63 ) {
+if ( $file eq '' || $c < 1 || $h < 1 || $h > 256 || $s < 1 || $s > 63 ) {
     print STDERR "Usage: $0 [-doFMz4][-i id] file c h s (max: 1024 256 63)\n";
     print STDERR "    -d    add DOSEMU header\n";
     print STDERR "    -o    print filesystem offset to stdout\n";
@@ -135,6 +134,14 @@ if ( $file eq '' || $c < 1 || $c > 1024 ||
     exit 1;
 }
 
+if ($c > 1024) {
+    print STDERR "Warning: more than 1024 cylinders ($c).\n";
+    print STDERR "Not all BIOSes will be able to boot this device.\n";
+    $cc = 1024;
+} else {
+    $cc = $c;
+}
+
 $cylsize = $h*$s*512;
 
 if ( !$is_open ) {
@@ -179,9 +186,11 @@ $bhead   = ($h > 1) ? 1 : 0;
 $bsect   = 1;
 $bcyl    = ($h > 1) ? 0 : 1;
 $ehead   = $h-1;
-$esect   = $s + ((($c-1) & 0x300) >> 2);
-$ecyl    = ($c-1) & 0xff;
-if ( $psize > 65536 ) {
+$esect   = $s + ((($cc-1) & 0x300) >> 2);
+$ecyl    = ($cc-1) & 0xff;
+if ( $cc > 1024 ) {
+    $fstype = 0x0e;
+} elsif ( $psize > 65536 ) {
     $fstype = 0x06;
 } else {
     $fstype = 0x04;
@@ -266,9 +275,15 @@ print OUTPUT pack("V", ($offset-$header_size)>>9);
 
 # Set the partition type
 if ( $opt{'F'} ) {
-    $fstype = 0x0b;		# FAT32
+    if ( $cc > 1024 ) {
+	$fstype = 0x0c;		# FAT32 LBA
+    } else {
+	$fstype = 0x0b;
+    }
 } else {
-    if ( $psize > 65536 ) {
+    if ( $cc > 1024 ) {
+	$fstype = 0x0e;		# FAT16 LBA
+    } elsif ( $psize > 65536 ) {
 	$fstype = 0x06;		# FAT16 > 32MB
     } else {
 	$fstype = 0x04;		# FAT16 <= 32MB