Hi,
Attaches is a draft of proposed bindings for New uImage format. It's a early RFC, please review and comment.
Cheers, Marian
U-boot New uImage format bindings definition ============================================
1) Introduction ---------------
Evolution of the 2.6 linux kernel for embedded PowerPC systems introduced new booting method which requires that hardware description is available to the kernel in the form of Flattened Device Tree.
Booting with a Flattened Device Tree is much more flexible and is intended to replace direct passing of 'struct bd_info' which was used to boot pre-FDT kernels.
However, U-boot needs to support both techniques to provide backward compatibility for platforms which are not FDT ready. Number of elements playing role in the booting process has increased and now includes the FDT blob. Kernel image, FDT blob and possibly ramdisk image - all must be placed in the system memory and passed to bootm as a arguments. Some of them may be missing, FDT is not present for legacy platforms, ramdisk is always optional. Additionally, old uImage format has been extended to support multi sub-images but the support is limited by simple format of the legacy uImage structure. Single binary header 'struct image_header' is not flexible enough to cover all possible scenarios.
All those factors combined clearly show that there is a need for new, more flexible, multi component uImage format.
2) New uImage format assumptions --------------------------------
a) Implementation
Libfdt has been selected for a New uImage format implementation as (1) it provides needed functionality, (2) is actively maintained and developed and (3) increases code reuse as it is already part of the U-boot source tree.
b) Terminology
This document defines New uImage structure by providing FDT bindings for new uImage internals. Bindings are defined from U-boot perspective, i.e. describe final form of the uImage at the moment when it reaches U-boot. User perspective may be simpler, as some of the properties (like timestamps and hashes) will need to be filled in automatically by the U-boot mkimage tool.
To avoid confusion with the kernel FDT the following naming convention is proposed for the New uImage format related terms:
FIT - Flattened uImage Tree
FIT is formally a flattened device tree (in the libfdt meaning), which conforms to bindigs defined in this document.
.its - image tree source .itb - image tree blob
c) Image building procedure
The following picture schows how the New uImage is prepared. Input consists of image source file (.its) and a set of data files. Image is created with the help of standard U-boot mkimage tool (approprietly extended) which in turn will use dtc (device tree compiler) to produce image tree blob (.itb). Resulting .itb file is is the actual binary of a New uImage.
tqm5200.its + vmlinux.bin.gz mkimage + dtc xfer to target eldk-4.2-ramdisk --------------> tqm5200.itb --------------> bootm tqm5200.dtb /|\ ... | 'New uImage'
- create .its file, automaticallu filled in properties are omitted - call mkimage tool on a .its file - mkimage calls dtc to create .itb image and assures that missing properites are added - .itb (New uImage) is uploaded onto the target and used therein
d) Identifiers used to uniq
To identify FIT sub-nodes representing images, hashes, configurations (which are defined in the following sections), the "unit name" of the given sub-node is used as it's identifier as it assures uniqueness without additional checking required.
3) Root node properties -----------------------
Root node of the uImage Tree should have the following layout:
/ o image-tree |- description = "image description" |- timestamp = <12399321> |- #address-cells = <1> | o images | | | o img@1 {...} | o img@2 {...} | ... | o configurations |- default = "cfg@1" | o cfg@1 {...} o cfg@2 {...} ...
Optional property: - description : Textual description of the uImage
Mandatory property: - timestamp : Last image modification time being counted in seconds since 1970-01-01 00:00:00 - to be automatically calculated by mkimage tool.
Conditionally mandatory property: - #address-cells : Number of 32bit cells required to represent entry and load addresses supplied within sub-image nodes. May be omitted when no entry or load addresses are used.
Mandatory node: - images : This node contains a set of sub-nodes, each of them representing single component sub-image (like kernel, ramdisk, etc.). At least one sub-image is required.
Optional node: - configurations : Contains a set of available configuration nodes and defines a default configuration.
4) '/images' node -----------------
This node is a conatiner node for component sub-image nodes. Each sub-node of the '/images' node should have the following layout:
o image@1 |- description = "component sub-image description" |- type = "sub-image type name" |- os = "OS name" |- arch = "ARCH name" |- data = {path/to/data/file.bin} |- compression = "compression name" |- size = <00001000> |- entry = <00000000> |- load = <00000000> | o hash@1 {...} o hash@2 {...} ...
Mandatory properties: - description : Textual description of the component sub-image - type : Name of component sub-image type, supported types are: "standalone", "kernel", "ramdisk", "firmware", "script", "filesystem", "fdt". - data : Path to the external file which contains this node's binary data.
NOTE: Currently dtc compiler does not support binary includes feature, appropriate extension is required. {/path/to/the/data/file.bin} is an example syntax for such feature, which may change when binary includes are implemented for dtc.
- size : One 32 bit cell representing this node's data size, i.e. size of data binary included by 'data' property). - compression : Compression used by included data. Supported compressions are "gzip" and "bzip2". If no compression is used compression property should be set to "none".
Conditionally mandatory property: - os : OS name, mandatory for type="kernel", valid OS names are: "openbsd", "netbsd", "freebsd", "4_4bsd", "linux", "svr4", "esix", "solaris", "irix", "sco", "dell", "ncr", "lynxos", "vxworks", "psos", "qnx", "u_boot", "rtems", "artos", "unity". - arch : Architecture name, mandatory for types: "standalone", "kernel", "firmware", "ramdisk" and "fdt". Valid architecture names are: "alpha", "arm", "i386", "ia64", "mips", "mips64", "ppc", "s390", "sh", "sparc", "sparc64", "m68k", "nios", "microblaze", "nios2", "blackfin", "avr32", "st200". - entry : entry point address, address size is determined by '#address-cells' property of the root node. Mandatory for for types: "standalone" and "kernel". - load : load address, address size is determined by '#address-cells' property of the root node. Mandatory for for types: "standalone" and "kernel".
Optional nodes: - hash@1 : Each hash sub-node represents separate hash or checksum calculated for node's data according to specified algorithm.
5) Hash nodes -------------
o hash@1 |- algo = "hash or checksum algorithm name" |- value = [hash or checksum value]
Mandatory properties: - algo : Algorithm name, supported are "crc32", "md5" and "sha1". - value : Actual checksum or hash value, correspondingly 4, 16 or 20 bytes long.
6) '/configurations' node -------------------------
The 'configurations' node is optional. If present, it allows to create a convenient, labled boot configurations, which combine together kernel images with their ramdisks and fdt blobs.
The 'configurations' node has has the following structure:
o configurations |- default = "default configuration sub-node unit name" | o config@1 {...} o config@2 {...} ...
Optional property: - default : Selects one of the configuration sub-nodes as a default configuration.
Mandatory nodes: - configuration-sub-node-unit-name : At least one of the configuration sub-nodes is required.
7) Configuration nodes ----------------------
Each configuration has the following struture:
o config@1 |- description = "configuration description" |- kernel = "kernel sub-node unit name" |- ramdisk = "ramdisk sub-node unit name" |- fdt = "fdt sub-node unit-name"
Mandatory properties: - description : Textual configuration description. - kernel : Unit name of the corresponding kernel image (image sub-node of a "kernel" type).
Optional properties: - ramdisk : Unit name of the corresponding ramdisk image (component image node of a "ramdisk" type). - fdt : Unit name of the corresponding fdt blob (component image node of a "fdt type").
The FDT blob is required to properly boot FDT based kernel, so the minimal configuration for 2.6 FDT kernel is (kernel, fdt) pair.
Older, 2.4 kernel and 2.6 non-FDT kernel do not use FDT blob, in such cases 'struct bd_info' must be passed instead of FDT blob, thus fdt property *must not* be specified in a configuration node.
Appendix - example .its files -----------------------------
Example 1 ---------
This example shows configuration for a very simple New uImage containing kernel image only - basicaly a equivalent of a legacy kernel uImage:
The .its file as prepared by the image creator:
/* * tqm5200.its - Simple U-boot uImage Source file for TQM5200 */ / { description = "2.4.25 linux kernels for tqm5200 "; images { kernel@1 { description = "vanilla-2.4.25"; type = "kernel"; os = "linux"; arch = "ppc"; data = {/home/my/images/vmlinux.bin.gz} compression = "gzip"; entry = <eeee1111>; load = <aaaa2222>; }; }; };
The same configuration, with the missing properties added by the mkimage tool:
/* * tqm5200.its - Simple U-boot uImage Source file for TQM5200 */ / { description = "2.4.25 linux kernels for tqm5200 "; timestamp = <12399321>; #address-cells = <1>;
images { kernel@1 { description = "vanilla-2.4.25";
type = "kernel"; os = "linux"; arch = "ppc";
data = {/home/my/images/vmlinux.bin.gz} compression = "gzip"; size = <00004444>;
entry = <eeee1111>; load = <aaaa2222>;
hash@1 { algo = "crc32"; value = [17255690]; }; }; }; };
Example 2 ---------
In this configuration more elements are added, few kernels, ramdisks and fdt blobs. Configuration section presents three handy configuration shortcuts. All properties are shown:
/* * tqm5200.its - U-boot uImage Source file for TQM5200 */ / { description = "2.6.23 linux kernels for tqm5200 "; timestamp = <12399321>; #address-cells = <1>;
images { kernel@1 { description = "vanilla-2.6.23";
type = "kernel"; os = "linux"; arch = "ppc";
data = {/home/my/images/vmlinux.bin.gz} compression = "gzip"; size = <00004444>;
entry = <eeee1111>; load = <aaaa2222>;
hash@1 { algo = "md5"; value = [12486fbaf78a25a7 36df432bf6390e2f]; }; hash@2 { algo = "sha1"; value = [12486fbaf78a25a7dedf 36df432bf6390e2f1123]; }; };
kernel@2 { description = "2.6.23-denx";
type = "kernel"; os = "linux"; arch = "ppc";
data = {/home/my/images/2.6.23-denx.bin.gz}; compression = "gzip"; size = <00004444>;
entry = <eeee1111>; load = <aaaa2222>;
hash@1 { algo = "sha1"; value = [12486fbaf78a25a7dedf 36df432bf6390e2f1123]; }; };
kernel@3 { description = "2.4.25-denx";
type = "kernel"; os = "linux"; arch = "ppc";
data = {/home/my/images/2.4.25-denx.bin.gz}; compression = "gzip"; size = <00004444>;
entry = <eeee1111>; load = <aaaa2222>;
hash@1 { algo = "md5"; value = [1123dffd]; }; };
ramdisk@1 { description = "eldk-4.2-ramdisk";
type = "ramdisk"; arch = "ppc";
data = {/home/my/images/eldk-4.2-ramdisk}; compression = "gzip"; size = <00004444>;
hash@1 { algo = "sha1"; value = [12486fbaf78a25a7dedf 36df432bf6390e2f1123]; }; };
ramdisk@2 { description = "eldk-3.1-ramdisk";
type = "ramdisk"; arch = "ppc";
data = {/home/my/images/eldk-3.1-ramdisk}; compression = "gzip"; size = <00004444>;
hash@1 { algo = "sha1"; value = [12486fbaf78a25a7dedf 36df432bf6390e2f1123]; }; };
fdt@1 { description = "tqm5200-fdt";
type = "fdt"; arch = "ppc";
data = {/home/my/images/tqm5200.dtb}; compression = "none"; size = <00004444>;
hash@1 { algo = "crc32"; value = [12486fba]; }; };
fdt@2 { description = "tqm5200s-fdt";
type = "fdt"; arch = "ppc";
data = {/home/my/images/tqm5200s.dtb}; compression = "none"; size = <00004444>;
hash@1 { algo = "crc32"; value = [12486fba]; }; };
app@1 { description = "standalone application";
type = "standalone"; os = "linux"; arch = "ppc";
data = {/home/my/images/app.bin} compression = "none"; size = <00004444>;
entry = <eeee1111>; load = <aaaa2222>;
hash@1 { algo = "sha1"; value = [12486fbaf78a25a7dedf 36df432bf6390e2f1123]; }; }; };
configurations { default = "config@1";
config@1 { description = "tqm5200 vanilla-2.6.23 configuration";
kernel = "kernel@1"; ramdisk = "ramdisk@1"; fdt = "fdt@1"; };
config@2 { description = "tqm5200s denx-2.6.23 configuration";
kernel = "kernel@2"; ramdisk = "ramdisk@1"; fdt = "fdt@2"; };
config@3 { description = "tqm5200s denx-2.4.25 configuration";
kernel = "kernel@3"; ramdisk = "ramdisk@2"; }; }; };