@@ -522,6 +522,7 @@ quiet_cmd_fit = FIT $@
cmd_fit = $(MAKE_FIT) -o $@ --arch $(UIMAGE_ARCH) --os linux \
--name '$(UIMAGE_NAME)' \
$(if $(findstring 1,$(KBUILD_VERBOSE)),-v) \
+ $(if $(FIT_DECOMPOSE_DTBS),--decompose-dtbs) \
--compress $(FIT_COMPRESSION) -k $< @$(word 2,$^)
# XZ
@@ -22,6 +22,11 @@ the entire FIT.
Use -c to compress the data, using bzip2, gzip, lz4, lzma, lzo and
zstd algorithms.
+Use -D to decompose "composite" DTBs into their base components and
+deduplicate the resulting base DTBs and DTB overlays. This requires the
+DTBs to be sourced from the kernel build directory, as the implementation
+looks at the .cmd files produced by the kernel build.
+
The resulting FIT can be booted by bootloaders which support FIT, such
as U-Boot, Linuxboot, Tianocore, etc.
@@ -64,6 +69,8 @@ def parse_args():
help='Specifies the architecture')
parser.add_argument('-c', '--compress', type=str, default='none',
help='Specifies the compression')
+ parser.add_argument('-D', '--decompose-dtbs', action='store_true',
+ help='Decompose composite DTBs into base DTB and overlays')
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,
@@ -140,12 +147,12 @@ def finish_fit(fsw, entries):
fsw.end_node()
seq = 0
with fsw.add_node('configurations'):
- for model, compat in entries:
+ for model, compat, files in entries:
seq += 1
with fsw.add_node(f'conf-{seq}'):
fsw.property('compatible', bytes(compat))
fsw.property_string('description', model)
- fsw.property_string('fdt', f'fdt-{seq}')
+ fsw.property('fdt', bytes(''.join(f'fdt-{x}\x00' for x in files), "ascii"))
fsw.property_string('kernel', 'kernel')
fsw.end_node()
@@ -193,21 +200,9 @@ def output_dtb(fsw, seq, fname, arch, compress):
fname (str): Filename containing the DTB
arch: FIT architecture, e.g. 'arm64'
compress (str): Compressed algorithm, e.g. 'gzip'
-
- Returns:
- tuple:
- 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 = inf.read()
- fdt = libfdt.FdtRo(data)
- model = fdt.getprop(0, 'model').as_str()
- compat = fdt.getprop(0, 'compatible')
-
- fsw.property_string('description', model)
+ fsw.property_string('description', os.path.basename(fname))
fsw.property_string('type', 'flat_dt')
fsw.property_string('arch', arch)
fsw.property_string('compression', compress)
@@ -215,9 +210,45 @@ def output_dtb(fsw, seq, fname, arch, compress):
with open(fname, 'rb') as inf:
compressed = compress_data(inf, compress)
fsw.property('data', compressed)
- return model, compat
+def process_dtb(fname, args):
+ """Process an input DTB, decomposing it if requested and is possible
+
+ Args:
+ fname (str): Filename containing the DTB
+ args (Namespace): Program arguments
+ Returns:
+ tuple:
+ str: Model name string
+ str: Root compatible string
+ files: list of filenames corresponding to the DTB
+ """
+ # Get the compatible / model information
+ with open(fname, 'rb') as inf:
+ data = inf.read()
+ fdt = libfdt.FdtRo(data)
+ model = fdt.getprop(0, 'model').as_str()
+ compat = fdt.getprop(0, 'compatible')
+
+ if args.decompose_dtbs:
+ # Check if the DTB needs to be decomposed
+ path, basename = os.path.split(fname)
+ cmd_fname = os.path.join(path, f'.{basename}.cmd')
+ with open(cmd_fname, 'r', encoding='ascii') as inf:
+ cmd = inf.read()
+
+ if 'scripts/dtc/fdtoverlay' in cmd:
+ # This depends on the structure of the composite DTB command
+ files = cmd.split()
+ files = files[files.index('-i') + 1:]
+ else:
+ files = [fname]
+ else:
+ files = [fname]
+
+ return (model, compat, files)
+
def build_fit(args):
"""Build the FIT from the provided files and arguments
@@ -235,6 +266,7 @@ def build_fit(args):
fsw = libfdt.FdtSw()
setup_fit(fsw, args.name)
entries = []
+ fdts = {}
# Handle the kernel
with open(args.kernel, 'rb') as inf:
@@ -243,12 +275,22 @@ def build_fit(args):
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])
+ # Ignore non-DTB (*.dtb) files
+ if os.path.splitext(fname)[1] != '.dtb':
+ continue
+
+ (model, compat, files) = process_dtb(fname, args)
+
+ for fn in files:
+ if fn not in fdts:
+ seq += 1
+ size += os.path.getsize(fn)
+ output_dtb(fsw, seq, fn, args.arch, args.compress)
+ fdts[fn] = seq
+
+ files_seq = [fdts[fn] for fn in files]
+
+ entries.append([model, compat, files_seq])
finish_fit(fsw, entries)
The kernel tree builds some "composite" DTBs, where the final DTB is the result of applying one or more DTB overlays on top of a base DTB with fdtoverlay. The FIT image specification already supports configurations having one base DTB and overlays applied on top. It is then up to the bootloader to apply said overlays and either use or pass on the final result. This allows the FIT image builder to reuse the same FDT images for multiple configurations, if such cases exist. The decomposition function depends on the kernel build system, reading back the .cmd files for the to-be-packaged DTB files to check for the fdtoverlay command being called. This will not work outside the kernel tree. The function is off by default to keep compatibility with possible existing users. To facilitate the decomposition and keep the code clean, the model and compatitble string extraction have been moved out of the output_dtb function. The FDT image description is replaced with the base file name of the included image. Signed-off-by: Chen-Yu Tsai <wenst@chromium.org> --- Changes since v1: - Replace OrderedDict with standard {} dict - Change short form command line argument to -D - Drop [] around "'fdt-{x}\x00' for x in files" - Add spaces around '+' in slice argument - Split out DTB parsing into separate function Simon's reviewed-by was dropped. This is a feature I alluded to in my replies to Simon's original submission of the make_fit.py script [1]. This is again made a runtime argument as not all firmware out there that boot FIT images support applying overlays. Like my previous submission for disabling compression for included FDT images, the bootloader found in RK3399 and MT8173 Chromebooks do not support applying overlays. Another case of this is U-boot shipped by development board vendors in binary form (without upstream) in an image or in SPI flash on the board that were built with OF_LIBFDT_OVERLAY=n. These would fail to boot FIT images with DT overlays. One such example is my Hummingboard Pulse. In these cases the firmware is either not upgradable or very hard to upgrade. I believe there is value in supporting these cases. A common script shipped with the kernel source that can be shared by distros means the distro people don't have to reimplement this in their downstream repos or meta-packages. For ChromeOS this means reducing the amount of package code we have in shell script. [1] https://lore.kernel.org/linux-kbuild/20231207142723.GA3187877@google.com/ scripts/Makefile.lib | 1 + scripts/make_fit.py | 86 ++++++++++++++++++++++++++++++++------------ 2 files changed, 65 insertions(+), 22 deletions(-)