diff options
Diffstat (limited to 'Documentation/powerpc/booting-without-of.txt')
| -rw-r--r-- | Documentation/powerpc/booting-without-of.txt | 29 |
1 files changed, 23 insertions, 6 deletions
diff --git a/Documentation/powerpc/booting-without-of.txt b/Documentation/powerpc/booting-without-of.txt index 6d5a5a0fa5e8..a1f83f1c24c9 100644 --- a/Documentation/powerpc/booting-without-of.txt +++ b/Documentation/powerpc/booting-without-of.txt @@ -265,6 +265,9 @@ struct boot_param_header { booting on */ /* version 3 fields below */ u32 size_dt_strings; /* size of the strings block */ + + /* version 17 fields below */ + u32 size_dt_struct; /* size of the DT structure block */ }; Along with the constants: @@ -335,10 +338,13 @@ struct boot_param_header { to reallocate it easily at boot and free up the unused flattened structure after expansion. Version 16 introduces a new more "compact" format for the tree itself that is however not backward - compatible. You should always generate a structure of the highest - version defined at the time of your implementation. Currently - that is version 16, unless you explicitly aim at being backward - compatible. + compatible. Version 17 adds an additional field, size_dt_struct, + allowing it to be reallocated or moved more easily (this is + particularly useful for bootloaders which need to make + adjustments to a device tree based on probed information). You + should always generate a structure of the highest version defined + at the time of your implementation. Currently that is version 17, + unless you explicitly aim at being backward compatible. - last_comp_version @@ -347,7 +353,7 @@ struct boot_param_header { is backward compatible with version 1 (that is, a kernel build for version 1 will be able to boot with a version 2 format). You should put a 1 in this field if you generate a device tree of - version 1 to 3, or 0x10 if you generate a tree of version 0x10 + version 1 to 3, or 16 if you generate a tree of version 16 or 17 using the new unit name format. - boot_cpuid_phys @@ -360,6 +366,17 @@ struct boot_param_header { point (see further chapters for more informations on the required device-tree contents) + - size_dt_strings + + This field only exists on version 3 and later headers. It + gives the size of the "strings" section of the device tree (which + starts at the offset given by off_dt_strings). + + - size_dt_struct + + This field only exists on version 17 and later headers. It gives + the size of the "structure" section of the device tree (which + starts at the offset given by off_dt_struct). So the typical layout of a DT block (though the various parts don't need to be in that order) looks like this (addresses go from top to @@ -417,7 +434,7 @@ root node who has no parent. A node has 2 names. The actual node name is generally contained in a property of type "name" in the node property list whose value is a zero terminated string and is mandatory for version 1 to 3 of the -format definition (as it is in Open Firmware). Version 0x10 makes it +format definition (as it is in Open Firmware). Version 16 makes it optional as it can generate it from the unit name defined below. There is also a "unit name" that is used to differentiate nodes with |