1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
|
# Flattened uImage Tree documentation
[uImage.FIT] is the new format used for uImage payloads developed by
[U-boot].
## Supported architectures
* aarch32
* aarch64
* riscv
## Supported FIT sections
The FIT can contain multiple sections, each holding a unique
kernel, initrd or config. Out of the sections one kernel and
one initrd is chosen, depending on the matching config.
The config is selected depending on the compat string.
The section must be named in order to be found by the FIT parser:
* kernel
* fdt
* ramdisk
## Architecture specifics
The FIT parser needs architecture support.
### aarch32
The source code can be found in `src/arch/arm/fit_payload.c`.
On aarch32 the kernel (a section named 'kernel') must be in **Image**
format and it needs a devicetree (a section named 'fdt') to boot.
The kernel will be placed close to "*DRAMSTART*".
### aarch64
The source code can be found in `src/arch/arm64/fit_payload.c`.
On aarch64 the kernel (a section named 'kernel') must be in **Image**
format and it needs a devicetree (a section named 'fdt') to boot.
The kernel will be placed close to "*DRAMSTART*".
### RISC-V
The source code can be found in `src/arch/riscv/fit_payload.c`.
On RISC-V the kernel (a section named 'kernel') must be in **Image**
format and it needs a devicetree (a section named 'fdt') to boot.
The kernel will be placed close to "*DRAMSTART*".
### Other
Other architectures aren't supported.
## Supported compression
The FIT image has to be included uncompressed into the CBFS. The sections
inside the FIT image can use different compression schemes.
Supported compression algorithms:
* LZMA
* LZ4
* none
## Compat string
The config entries contain a compatible string, that is used to find a
matching config.
The following mainboard specific functions provide the BOARDID and SKUID:
```c
uint32_t board_id(void);
```
```c
uint32_t sku_id(void);
```
By default the following compat strings are added:
* *CONFIG_MAINBOARD_VENDOR*,*CONFIG_MAINBOARD_PART_NUMBER*
* *CONFIG_MAINBOARD_VENDOR*,*CONFIG_MAINBOARD_PART_NUMBER*-rev*BOARDID*
* *CONFIG_MAINBOARD_VENDOR*,*CONFIG_MAINBOARD_PART_NUMBER*-rev*BOARDID*-sku*SKUID*
Example:
```
cavium,cn8100_sff_evb
```
If *board_id()* or *sku_id()* return invalid, the single comapt string isn't added.
You can add custom compat strings by calling:
```c
fit_add_compat_string(const char *str);
```
If no matching compat string is found, the default config is chosen.
## Building FIT image
The FIT image has to be built by calling `mkimage`. You can use
the following example configuration:
```
/*
* Simple U-Boot uImage source file containing a single kernel and FDT blob
*/
/dts-v1/;
/ {
description = "Simple image with single Linux kernel and FDT blob";
#address-cells = <1>;
images {
kernel {
description = "Vanilla Linux kernel";
data = /incbin/("Image.lzma");
type = "kernel";
arch = "arm64";
os = "linux";
compression = "lzma";
load = <0x80000>;
entry = <0x80000>;
hash-1 {
algo = "crc32";
};
};
fdt-1 {
description = "Flattened Device Tree blob";
data = /incbin/("target.dtb");
type = "flat_dt";
arch = "arm64";
compression = "none";
hash-1 {
algo = "crc32";
};
};
ramdisk-1 {
description = "Compressed Initramfs";
data = /incbin/("initramfs.cpio.xz");
type = "ramdisk";
arch = "arm64";
os = "linux";
compression = "none";
load = <00000000>;
entry = <00000000>;
hash-1 {
algo = "sha1";
};
};
};
configurations {
default = "conf-1";
conf-1 {
description = "Boot Linux kernel with FDT blob";
kernel = "kernel";
fdt = "fdt-1";
ramdisk = "ramdisk-1";
};
};
};
```
Save it as ITS file `config.its` along with the other files defined here:
* target.dtb
* initramfs.cpio.xz
* Image.lzma
Generate the `uImage` that will be included into the CBFS by calling
```bash
mkimage -f config.its uImage
```
The generated file includes a compressed initrd **initramfs.cpio.xz**, which
will be decompressed by the Linux kernel, a compressed kernel **Image.lzma**,
which will be decompressed by the FIT loader and an uncompressed devicetree blob.
[uImage.FIT]: https://raw.githubusercontent.com/u-boot/u-boot/master/doc/uImage.FIT/howto.txt
[U-Boot]: https://www.denx.de/wiki/U-Boot
|
