pkgs/os-specific/linux/device-tree/apply_overlays.py

   1 from argparse import ArgumentParser
   2 from dataclasses import dataclass
   3 from functools import cached_property
   4 import json
   5 from pathlib import Path
   6
   7 from libfdt import Fdt, FdtException, FDT_ERR_NOSPACE, fdt_overlay_apply
   8
   9
  10 @dataclass
  11 class Overlay:
  12     name: str
  13     filter: str
  14     dtbo_file: Path
  15
  16     @cached_property
  17     def fdt(self):
  18         with self.dtbo_file.open("rb") as fd:
  19             return Fdt(fd.read())
  20
  21     @cached_property
  22     def compatible(self):
  23         return get_compatible(self.fdt)
  24
  25
  26 def get_compatible(fdt):
  27     root_offset = fdt.path_offset("/")
  28     return set(fdt.getprop(root_offset, "compatible").as_stringlist())
  29
  30
  31 def apply_overlay(dt: Fdt, dto: Fdt) -> Fdt:
  32     while True:
  33         # we need to copy the buffers because they can be left in an inconsistent state
  34         # if the operation fails (ref: fdtoverlay source)
  35         result = dt.as_bytearray().copy()
  36         err = fdt_overlay_apply(result, dto.as_bytearray().copy())
  37
  38         if err == 0:
  39             new_dt = Fdt(result)
  40             # trim the extra space from the final tree
  41             new_dt.pack()
  42             return new_dt
  43
  44         if err == -FDT_ERR_NOSPACE:
  45             # not enough space, add some blank space and try again
  46             # magic number of more space taken from fdtoverlay
  47             dt.resize(dt.totalsize() + 65536)
  48             continue
  49
  50         raise FdtException(err)
  51
  52 def main():
  53     parser = ArgumentParser(description='Apply a list of overlays to a directory of device trees')
  54     parser.add_argument("--source", type=Path, help="Source directory")
  55     parser.add_argument("--destination", type=Path, help="Destination directory")
  56     parser.add_argument("--overlays", type=Path, help="JSON file with overlay descriptions")
  57     args = parser.parse_args()
  58
  59     source: Path = args.source
  60     destination: Path = args.destination
  61     overlays: Path = args.overlays
  62
  63     with overlays.open() as fd:
  64         overlays_data = [
  65             Overlay(
  66                 name=item["name"],
  67                 filter=item["filter"],
  68                 dtbo_file=Path(item["dtboFile"]),
  69             )
  70             for item in json.load(fd)
  71         ]
  72
  73     for source_dt in source.glob("**/*.dtb"):
  74         rel_path = source_dt.relative_to(source)
  75
  76         print(f"Processing source device tree {rel_path}...")
  77         with source_dt.open("rb") as fd:
  78             dt = Fdt(fd.read())
  79
  80         dt_compatible = get_compatible(dt)
  81
  82         for overlay in overlays_data:
  83             if overlay.filter and overlay.filter not in str(rel_path):
  84                 print(f"  Skipping overlay {overlay.name}: filter does not match")
  85                 continue
  86
  87             if not overlay.compatible.intersection(dt_compatible):
  88                 print(f"  Skipping overlay {overlay.name}: {overlay.compatible} is incompatible with {dt_compatible}")
  89                 continue
  90
  91             print(f"  Applying overlay {overlay.name}")
  92             dt = apply_overlay(dt, overlay.fdt)
  93
  94         print(f"Saving final device tree {rel_path}...")
  95         dest_path = destination / rel_path
  96         dest_path.parent.mkdir(parents=True, exist_ok=True)
  97         with dest_path.open("wb") as fd:
  98             fd.write(dt.as_bytearray())
  99
 100
 101 if __name__ == '__main__':
 102     main()