Allow a 'paths-relative-to' key in the firmware config

docs/fw_binaries.md

@@ -10,6 +10,7 @@ explains what firmware and configuration options are needed for each SoC family.
 A firmware configuration file for snagrecover has the following structure:
 
 ```
+paths-relative-to: THIS_FILE
 fw_1:
   path: /path/to/fw_1
   option1: value1
@@ -28,6 +29,20 @@ type of SoC you are using, you will probably want to configure your U-Boot build
 so that it can interact with snagflash correctly after recovery (e.g. use DFU,
 UMS or fastboot).
 
+The key `paths-relative-to` is optional and indicates that paths to images are
+relative to a specific path, either:
+
+- `CWD`: the current working directory, e.g the default behaviour
+- `THIS_FILE`: the directory containing the current configuration file
+- a path to a directory.
+
+If `THIS_FILE` or a path is specified, snagrecover will effectively join this
+path and the images paths. `CWD` is actually a no-op and will keep the default
+behaviour.
+Absolute paths to images will not be modified by this option.
+
+This is useful when distributing the configuration file alongside images.
+
 ## General tips on configuring U-Boot
 
 In many cases, in can be necessary to build the recovery U-Boot yourself e.g.

src/snagrecover/config.py

@@ -17,6 +17,7 @@
 # along with this program; if not, write to the Free Software
 # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 
+import os
 import yaml
 from snagrecover.utils import (
 	cli_error,
@@ -93,6 +94,20 @@ def check_soc_model(soc_model: str):
 	return None
 
 
+def complete_fw_paths(fw_config: dict, this_file_path: str) -> None:
+    paths_relative_to_conf = fw_config.pop("paths-relative-to", "CWD")
+    if paths_relative_to_conf == "CWD":
+        return
+    elif paths_relative_to_conf == "THIS_FILE":
+        path_relative_to = os.path.dirname(this_file_path)
+    else:
+        path_relative_to = path_relative_to_conf
+
+    for binary in fw_config.keys():
+        if "path" in fw_config[binary]:
+            fw_config[binary]["path"] = os.path.join(path_relative_to, fw_config[binary]["path"])
+
+
 def init_config(args: list):
 	# this is the only time that config.recovery_config should be modified!
 	# get soc model
@@ -138,11 +153,13 @@ def init_config(args: list):
 		# get firmware configs
 		for path in args.firmware_file:
 			with open(path, "r") as file:
-				fw_configs = {**fw_configs, **yaml.safe_load(file)}
-		if not isinstance(fw_configs, dict):
-			cli_error(
-				f"firmware config passed to CLI did not evaluate to dict: {fw_configs}"
-			)
+				fw_config_file = yaml.safe_load(file)
+			if not isinstance(fw_config_file, dict):
+				cli_error(
+					f"firmware config passed to CLI did not evaluate to dict: {fw_configs}"
+				)
+			complete_fw_paths(fw_config_file, path)
+			fw_configs = {**fw_configs, **fw_config_file}
 		recovery_config["firmware"] = fw_configs
 
 	# store input arguments in config