From e30ec7d4c74c545c9817ce5c6b2006675fabc519 Mon Sep 17 00:00:00 2001
From: Thomas Schmitt <scdbackup@gmx.net>
Date: Thu, 7 Apr 2011 18:04:16 +0000
Subject: [PATCH] Updated partition offset wiki about cylinder alignment

---
 libisoburn/trunk/doc/partition_offset.wiki | 40 ++++++++++++++++++----
 1 file changed, 34 insertions(+), 6 deletions(-)

diff --git a/libisoburn/trunk/doc/partition_offset.wiki b/libisoburn/trunk/doc/partition_offset.wiki
index ff35e7a9..33730f03 100644
--- a/libisoburn/trunk/doc/partition_offset.wiki
+++ b/libisoburn/trunk/doc/partition_offset.wiki
@@ -131,7 +131,7 @@ was edited to replace in the options of the xorriso command:
 }}}
 by
 {{{
-  -partition_offset 16 -no-pad --no-emul-toc
+  -partition_offset 16 -no-pad
 }}}
 Then GRUB 2 was built and installed.
 
@@ -142,10 +142,24 @@ The resulting image from
 was put onto USB stick. It passed the same tests on Debian
 as above RIPLinux example. It boots to a GRUB prompt.
 
-Due to options -no-pad --no-emul-toc the image is about 300 kB smaller than
+Due to option -no-pad the image is about 250 kB smaller than
 the image produced by original grub-mkrescue. Else it would have grown by
-about 130 kB. The mkisofs emulation of newer versions of xorriso has
---no-emul-toc as default. Thus the overhead would only be about 50 kB.
+about 50 kB.
+
+Unpadded ISO images are safe except for burning on CD in TAO mode.
+In this case problems may occur with reading the last few data blocks.
+So when burning onto CD make sure to require SAO mode and/or to
+require padding by 300 KiB.
+Burning on DVD or BD needs no such caution. Neither does copying
+on USB stick or hard disk.
+
+Program fdisk will complain about "different physical/logical" addresses.
+This can be silenced by adding option
+{{{
+ -partition_cyl_align on
+}}}
+at the cost of image padding up to the next full MiB.
+E.g. by 402 KiB to 2 MiB.
 
 --------------------------------------------------------------------------
 
@@ -162,12 +176,15 @@ preparations.
 
 Application:
 
-The partition offset feature can be controlled by libisofs API call
+The partition offset feature can be controlled by libisofs API calls
 {{{
 int iso_write_opts_set_part_offset(IsoWriteOpts *opts,
                                    uint32_t block_offset_2k,
                                    int secs_512_per_head,
                                    int heads_per_cyl);
+
+int iso_write_opts_set_system_area(IsoWriteOpts *opts, char data[32768],
+                                   int options, int flag);
 }}}
 resp. by libisoburn calls
 {{{
@@ -178,13 +195,24 @@ int isoburn_igopt_set_part_offset(struct isoburn_imgen_opts  *opts,
 int isoburn_igopt_get_part_offset(struct isoburn_imgen_opts *opts,
                                   uint32_t *block_offset_2k,
                                   int *secs_512_per_head, int *heads_per_cyl);
+
+int isoburn_igopt_set_system_area(struct isoburn_imgen_opts *o,
+                                  char data[32768], int options);
+
+int isoburn_igopt_get_system_area(struct isoburn_imgen_opts *o,
+                                  char data[32768], int *options);
 }}}
 resp. by xorriso options
 {{{
   -boot_image any partition_offset=(2kb_block_adr)
   -boot_image any partition_sec_hd=(number)
   -boot_image any partition_hd_cyl=(number)
-  -as mkisofs ... -partition_offset (2kb_block_adr) ...
+  -boot_image any partition_cyl_align(on|auto|off)
+
+  -as mkisofs ... -partition_offset (2kb_block_adr) \
+                  -partition_hd_cyl (number) \
+                  -partition_sec_hd (number) \
+                  -partition_cyl_align (on|auto|off) ...
 }}}
 
 As stated above, an offset larger than 16 would expose vital parts of the