blob: 263147df80a445aaed75101fcb8179662f0de380 [file] [log] [blame]
#!/usr/bin/env python3
# SPDX-License-Identifier: GPL-2.0+
# Copyright 2024 Google LLC
# Written by Simon Glass <>
"""Build a FIT containing a lot of devicetree files
Usage: -A arm64 -n 'Linux-6.6' -O linux
-o arch/arm64/boot/ -k /tmp/kern/arch/arm64/boot/image.itk
@arch/arm64/boot/dts/dtbs-list -E -c gzip
Creates a FIT containing the supplied kernel and a set of devicetree files,
either specified individually or listed in a file (with an '@' prefix).
Use -E to generate an external FIT (where the data is placed after the
FIT data structure). This allows parsing of the data without loading
the entire FIT.
Use -c to compress the data, using bzip2, gzip, lz4, lzma, lzo and
zstd algorithms.
The resulting FIT can be booted by bootloaders which support FIT, such
as U-Boot, Linuxboot, Tianocore, etc.
Note that this tool does not yet support adding a ramdisk / initrd.
import argparse
import collections
import os
import subprocess
import sys
import tempfile
import time
import libfdt
# Tool extension and the name of the command-line tools
CompTool = collections.namedtuple('CompTool', 'ext,tools')
'bzip2': CompTool('.bz2', 'bzip2'),
'gzip': CompTool('.gz', 'pigz,gzip'),
'lz4': CompTool('.lz4', 'lz4'),
'lzma': CompTool('.lzma', 'lzma'),
'lzo': CompTool('.lzo', 'lzop'),
'zstd': CompTool('.zstd', 'zstd'),
def parse_args():
"""Parse the program ArgumentParser
Namespace object containing the arguments
epilog = 'Build a FIT from a directory tree containing .dtb files'
parser = argparse.ArgumentParser(epilog=epilog, fromfile_prefix_chars='@')
parser.add_argument('-A', '--arch', type=str, required=True,
help='Specifies the architecture')
parser.add_argument('-c', '--compress', type=str, default='none',
help='Specifies the compression')
parser.add_argument('-E', '--external', action='store_true',
help='Convert the FIT to use external data')
parser.add_argument('-n', '--name', type=str, required=True,
help='Specifies the name')
parser.add_argument('-o', '--output', type=str, required=True,
help='Specifies the output file (.fit)')
parser.add_argument('-O', '--os', type=str, required=True,
help='Specifies the operating system')
parser.add_argument('-k', '--kernel', type=str, required=True,
help='Specifies the (uncompressed) kernel input file (.itk)')
parser.add_argument('-v', '--verbose', action='store_true',
help='Enable verbose output')
parser.add_argument('dtbs', type=str, nargs='*',
help='Specifies the devicetree files to process')
return parser.parse_args()
def setup_fit(fsw, name):
"""Make a start on writing the FIT
Outputs the root properties and the 'images' node
fsw (libfdt.FdtSw): Object to use for writing
name (str): Name of kernel image
fsw.INC_SIZE = 65536
fsw.property_string('description', f'{name} with devicetree set')
fsw.property_u32('#address-cells', 1)
fsw.property_u32('timestamp', int(time.time()))
def write_kernel(fsw, data, args):
"""Write out the kernel image
Writes a kernel node along with the required properties
fsw (libfdt.FdtSw): Object to use for writing
data (bytes): Data to write (possibly compressed)
args (Namespace): Contains necessary strings:
arch: FIT architecture, e.g. 'arm64'
fit_os: Operating Systems, e.g. 'linux'
name: Name of OS, e.g. 'Linux-6.6.0-rc7'
compress: Compression algorithm to use, e.g. 'gzip'
with fsw.add_node('kernel'):
fsw.property_string('type', 'kernel_noload')
fsw.property_string('arch', args.arch)
fsw.property_string('os', args.os)
fsw.property_string('compression', args.compress)'data', data)
fsw.property_u32('load', 0)
fsw.property_u32('entry', 0)
def finish_fit(fsw, entries):
"""Finish the FIT ready for use
Writes the /configurations node and subnodes
fsw (libfdt.FdtSw): Object to use for writing
entries (list of tuple): List of configurations:
str: Description of model
str: Compatible stringlist
seq = 0
with fsw.add_node('configurations'):
for model, compat in entries:
seq += 1
with fsw.add_node(f'conf-{seq}'):'compatible', bytes(compat))
fsw.property_string('description', model)
fsw.property_string('fdt', f'fdt-{seq}')
fsw.property_string('kernel', 'kernel')
def compress_data(inf, compress):
"""Compress data using a selected algorithm
inf (IOBase): Filename containing the data to compress
compress (str): Compression algorithm, e.g. 'gzip'
bytes: Compressed data
if compress == 'none':
comp = COMP_TOOLS.get(compress)
if not comp:
raise ValueError(f"Unknown compression algorithm '{compress}'")
with tempfile.NamedTemporaryFile() as comp_fname:
with open(, 'wb') as outf:
done = False
for tool in','):
try:[tool, '-c'], stdin=inf, stdout=outf)
done = True
except FileNotFoundError:
if not done:
raise ValueError(f'Missing tool(s): {}\n')
with open(, 'rb') as compf:
comp_data =
return comp_data
def output_dtb(fsw, seq, fname, arch, compress):
"""Write out a single devicetree to the FIT
fsw (libfdt.FdtSw): Object to use for writing
seq (int): Sequence number (1 for first)
fname (str): Filename containing the DTB
arch: FIT architecture, e.g. 'arm64'
compress (str): Compressed algorithm, e.g. 'gzip'
str: Model name
bytes: Compatible stringlist
with fsw.add_node(f'fdt-{seq}'):
# Get the compatible / model information
with open(fname, 'rb') as inf:
data =
fdt = libfdt.FdtRo(data)
model = fdt.getprop(0, 'model').as_str()
compat = fdt.getprop(0, 'compatible')
fsw.property_string('description', model)
fsw.property_string('type', 'flat_dt')
fsw.property_string('arch', arch)
fsw.property_string('compression', compress)
with open(fname, 'rb') as inf:
compressed = compress_data(inf, compress)'data', compressed)
return model, compat
def build_fit(args):
"""Build the FIT from the provided files and arguments
args (Namespace): Program arguments
bytes: FIT data
int: Number of configurations generated
size: Total uncompressed size of data
seq = 0
size = 0
fsw = libfdt.FdtSw()
entries = []
# Handle the kernel
with open(args.kernel, 'rb') as inf:
comp_data = compress_data(inf, args.compress)
size += os.path.getsize(args.kernel)
write_kernel(fsw, comp_data, args)
for fname in args.dtbs:
# Ignore overlay (.dtbo) files
if os.path.splitext(fname)[1] == '.dtb':
seq += 1
size += os.path.getsize(fname)
model, compat = output_dtb(fsw, seq, fname, args.arch, args.compress)
entries.append([model, compat])
finish_fit(fsw, entries)
# Include the kernel itself in the returned file count
return fsw.as_fdt().as_bytearray(), seq + 1, size
def run_make_fit():
"""Run the tool's main logic"""
args = parse_args()
out_data, count, size = build_fit(args)
with open(args.output, 'wb') as outf:
ext_fit_size = None
if args.external:
mkimage = os.environ.get('MKIMAGE', 'mkimage')
subprocess.check_call([mkimage, '-E', '-F', args.output],
with open(args.output, 'rb') as inf:
data =
ext_fit = libfdt.FdtRo(data)
ext_fit_size = ext_fit.totalsize()
if args.verbose:
comp_size = len(out_data)
print(f'FIT size {comp_size:#x}/{comp_size / 1024 / 1024:.1f} MB',
if ext_fit_size:
print(f', header {ext_fit_size:#x}/{ext_fit_size / 1024:.1f} KB',
print(f', {count} files, uncompressed {size / 1024 / 1024:.1f} MB')
if __name__ == "__main__":