colibri_imx6: fix video stdout in default environment

[oweals/u-boot.git] / doc / README.gpt

diff --git a/doc/README.gpt b/doc/README.gpt
index 35902ce0c882fd8be6d6279046085528307da39d..facd7afc3acdb70560096d3cdc417a68b734ae3f 100644 (file)
--- a/doc/README.gpt
+++ b/doc/README.gpt
@@ -1,10 +1,8 @@
+# SPDX-License-Identifier: GPL-2.0+
 #
 #  Copyright (C) 2012 Samsung Electronics
 #
 #  Lukasz Majewski <l.majewski@samsung.com>
-#
-#
-# SPDX-License-Identifier:     GPL-2.0+
 
 Glossary:
 ========
@@ -142,6 +140,10 @@ of the Primary.
 
           Attribute flags:
           Bit 0  - System partition
+          Bit 1  - Hide from EFI
+          Bit 2  - Legacy BIOS bootable
+          Bit 48-63 - Defined and used by the individual partition type
+          For Basic data partition :
           Bit 60 - Read-only
           Bit 62 - Hidden
           Bit 63 - Not mount
@@ -152,25 +154,89 @@ Creating GPT partitions in U-Boot:
 To restore GUID partition table one needs to:
 1. Define partition layout in the environment.
    Format of partitions layout:
-     "partitions=uuid_disk=...;name=u-boot,size=60MiB,uuid=...;
+     "uuid_disk=...;name=u-boot,size=60MiB,uuid=...;
        name=kernel,size=60MiB,uuid=...;"
      or
-     "partitions=uuid_disk=${uuid_gpt_disk};name=${uboot_name},
+     "uuid_disk=${uuid_gpt_disk};name=${uboot_name},
        size=${uboot_size},uuid=${uboot_uuid};"
 
    The fields 'name' and 'size' are mandatory for every partition.
    The field 'start' is optional.
 
+   If field 'size' of the last partition is 0, the partition is extended
+   up to the end of the device.
+
    The fields 'uuid' and 'uuid_disk' are optional if CONFIG_RANDOM_UUID is
    enabled. A random uuid will be used if omitted or they point to an empty/
    non-existent environment variable. The environment variable will be set to
-   the generated UUID.
+   the generated UUID.  The 'gpt guid' command reads the current value of the
+   uuid_disk from the GPT.
+
+   The field 'bootable' is optional, it is used to mark the GPT partition
+   bootable (set attribute flags "Legacy BIOS bootable").
+     "name=u-boot,size=60MiB;name=boot,size=60Mib,bootable;name=rootfs,size=0"
+   It can be used to locate bootable disks with command
+   "part list <interface> <dev> -bootable <varname>",
+   please check out doc/README.distro for use.
 
 2. Define 'CONFIG_EFI_PARTITION' and 'CONFIG_CMD_GPT'
 
-2. From u-boot prompt type:
+3. From u-boot prompt type:
    gpt write mmc 0 $partitions
 
+Checking (validating) GPT partitions in U-Boot:
+===============================================
+
+Procedure is the same as above. The only change is at point 3.
+
+At u-boot prompt one needs to write:
+   gpt verify mmc 0 [$partitions]
+
+where [$partitions] is an optional parameter.
+
+When it is not provided, only basic checks based on CRC32 calculation for GPT
+header and PTEs are performed.
+When provided, additionally partition data - name, size and starting
+offset (last two in LBA) - are compared with data defined in '$partitions'
+environment variable.
+
+After running this command, return code is set to 0 if no errors found in
+on non-volatile medium stored GPT.
+
+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
+doc/arch/index.rst:
+
+=>host bind 0 ./disk.raw
+=> gpt read host 0
+[ . . . ]
+=> gpt swap host 0 name othername
+[ . . . ]
+
 Partition type GUID:
 ====================
 
@@ -180,7 +246,7 @@ PARTITION_BASIC_DATA_GUID (EBD0A0A2-B9E5-4433-87C0-68B6B72699C7).
 If you define 'CONFIG_PARTITION_TYPE_GUID', a optionnal parameter 'type'
 can specify a other partition type guid:
 
-     "partitions=uuid_disk=...;name=u-boot,size=60MiB,uuid=...;
+     "uuid_disk=...;name=u-boot,size=60MiB,uuid=...;
        name=kernel,size=60MiB,uuid=...,
        type=0FC63DAF-8483-4772-8E79-3D69D8477DE4;"
 
@@ -202,7 +268,7 @@ Some strings can be also used at the place of known GUID :
        "lvm"    = PARTITION_LINUX_LVM_GUID
                   (E6D6D379-F507-44C2-A23C-238F2A3DF928)
 
-    "partitions=uuid_disk=...;name=u-boot,size=60MiB,uuid=...;
+    "uuid_disk=...;name=u-boot,size=60MiB,uuid=...;
        name=kernel,size=60MiB,uuid=...,type=linux;"
 
 They are also used to display the type of partition in "part list" command.