GPT: provide commands to selectively rename partitions

This patch provides support in u-boot for renaming GPT
partitions.  The renaming is accomplished via new 'gpt swap'
and 'gpt rename' commands.

The 'swap' mode returns an error if no matching partition names
are found, or if the number of partitions with one name does not equal
the number with the second name.   The 'rename' variant always
succeeds as long as a partition with the provided number exists.

Rewriting the partition table has the side-effect that all partitions
end up with "msftdata" flag set.  The reason is that partition type
PARTITION_BASIC_DATA_GUID is hard-coded in the gpt_fill_pte()
function.  This does not appear to cause any harm.

Signed-off-by: Alison Chaiken <alison@peloton-tech.com>

1 files changed, 19 insertions, 1 deletions

diff --git a/doc/README.gpt b/doc/README.gpt
index c415145236..517df551e7 100644
--- a/doc/README.gpt
+++ b/doc/README.gpt
@@ -210,6 +210,24 @@ Following line can be used to assess if GPT verification has succeed:
 U-BOOT> gpt verify mmc 0 $partitions
 U-BOOT> if test $? = 0; then echo "GPT OK"; else echo "GPT ERR"; fi
 
+Renaming GPT partitions from U-Boot:
+====================================
+
+GPT partition names are a mechanism via which userspace and U-Boot can
+communicate about software updates and boot failure.  The 'gpt guid',
+'gpt read', 'gpt rename' and 'gpt swap' commands facilitate
+programmatic renaming of partitions from bootscripts by generating and
+modifying the partitions layout string.  Here is an illustration of
+employing 'swap' to exchange 'primary' and 'backup' partition names:
+
+U-BOOT> gpt swap mmc 0 primary backup
+
+Afterwards, all partitions previously named 'primary' will be named
+'backup', and vice-versa.  Alternatively, single partitions may be
+renamed.  In this example, mmc0's first partition will be renamed
+'primary':
+
+U-BOOT> gpt rename mmc 0 1 primary
 
 The GPT functionality may be tested with the 'sandbox' board by
 creating a disk image as described under 'Block Device Emulation' in
@@ -228,7 +246,7 @@ board/sandbox/README.sandbox:
 =>host bind 0 ./disk.raw
 => gpt read host 0
 [ . . . ]
-=> gpt flip host 0
+=> gpt swap host 0 name othername
 [ . . . ]
 
 Partition type GUID: