Add DevicetreeAutoDirectory option for dynamic DTB discovery

Adds DevicetreeAutoDirectory= config option to complement the
DevicetreeAuto= list. This recursively scans the specified directory for
.dtb files and includes them as .dtbauto sections in UKI builds.

This is useful for when the full list of dtbs to include is not known at
configuration time.

Author: craftyguy

mkosi/__init__.py

@@ -1585,16 +1585,22 @@ def find_devicetree(context: Context, kver: str) -> Path:
     die(f"Requested devicetree {context.config.devicetree} not found")
 
 
-def find_devicetrees_auto(context: Context, kver: str) -> list[Path]:
+def find_devicetrees_auto(context: Context, kver: str, directory: Optional[Path] = None) -> list[Path]:
     dtbs: list[Path] = []
 
+    # Search for any listed devicetrees
     for d in (
         context.root / f"usr/lib/firmware/{kver}/device-tree",
         context.root / f"usr/lib/linux-image-{kver}",
         context.root / f"usr/lib/modules/{kver}/dtb",
     ):
         dtbs.extend(d.rglob("*.dtb"))
 
+    # Search for devicetrees in a given directory
+    if directory:
+        dtb_dir = context.root / os.fspath(directory).lstrip("/")
+        dtbs.extend(dtb_dir.rglob("*.dtb"))
+
     return dtbs
 
 
@@ -1760,8 +1766,8 @@ def build_uki(
         arguments += ["--devicetree", workdir(dtb)]
         options += ["--ro-bind", dtb, workdir(dtb)]
 
-    if context.config.devicetree_auto:
-        dtbs_auto = find_devicetrees_auto(context, kver)
+    if context.config.devicetree_auto or context.config.devicetree_auto_directory:
+        dtbs_auto = find_devicetrees_auto(context, kver, context.config.devicetree_auto_directory)
         for dtb in dtbs_auto:
             arguments += ["--devicetree-auto", workdir(dtb)]
             options += ["--ro-bind", dtb, workdir(dtb)]

mkosi/config.py

@@ -2015,6 +2015,7 @@ class Config:
     microcode_host: bool
     devicetree: Optional[Path]
     devicetree_auto: list[Path]
+    devicetree_auto_directory: Optional[Path]
     splash: Optional[Path]
     kernel_command_line: list[str]
     kernel_modules_include: list[str]
@@ -3173,6 +3174,12 @@ def parse_kernel_module_filter_regexp(p: str) -> str:
         parse=config_make_list_parser(delimiter=",", parse=make_path_parser(required=False)),
         help="Devicetrees for automatic hardware-based selection in UKI builds",
     ),
+    ConfigSetting(
+        dest="devicetree_auto_directory",
+        section="Content",
+        parse=config_make_path_parser(required=False),
+        help="Directory containing devicetrees for automatic hardware-based selection",
+    ),
     ConfigSetting(
         dest="splash",
         section="Content",
@@ -5478,6 +5485,7 @@ def summary(config: Config) -> str:
            Initrd Volatile Packages: {line_join_list(config.initrd_volatile_packages)}
                          Devicetree: {none_to_none(config.devicetree)}
                     Devicetree Auto: {line_join_list(config.devicetree_auto)}
+          Devicetree Auto Directory: {none_to_none(config.devicetree_auto_directory)}
                              Splash: {none_to_none(config.splash)}
                 Kernel Command Line: {line_join_list(config.kernel_command_line)}
                      Kernel Modules: {line_join_list(config.kernel_modules_include)}

mkosi/resources/man/mkosi.1.md

@@ -1089,6 +1089,14 @@ boolean argument: either `1`, `yes`, or `true` to enable, or `0`, `no`,
     when both are specified. Only affects UKI builds; ignored for Type 1 boot
     entries which support single devicetree only.
 
+`DevicetreeAutoDirectory=`, `--devicetree-auto-directory=`
+:   Directory containing Devicetree blobs for automatic hardware-based selection
+    in UKI builds. All `.dtb` files found recursively in this directory are
+    included as `.dtbauto` sections. Results are merged with `DevicetreeAuto=`
+    list entries. Useful when DTB requirements are determined after
+    configuration time (e.g. in finalize.) Only affects UKI builds; ignored for
+    Type 1 boot entries which support single devicetree only.
+
 `Splash=`, `--splash=`
 :   When set, the boot splash for any unified kernel image built by **mkosi** will
     be picked up from the given path inside the image.

tests/test_json.py

@@ -155,6 +155,7 @@ def test_config() -> None:
                 "vendor/board1.dtb",
                 "vendor/board2.dtb"
             ],
+            "DevicetreeAutoDirectory": "boot/dtbs",
             "Distribution": "fedora",
             "Drives": [
                 {
@@ -516,6 +517,7 @@ def test_config() -> None:
         microcode_host=True,
         devicetree=Path("freescale/imx8mm-verdin-nonwifi-dev.dtb"),
         devicetree_auto=[Path("vendor/board1.dtb"), Path("vendor/board2.dtb")],
+        devicetree_auto_directory=Path("boot/dtbs"),
         minimum_version="123",
         mirror=None,
         nspawn_settings=None,