stages: Add org.osbuild.write-device stage

This stage writes a file to a device using dd. This is a
rewrite/backport of one of the stages in osbuild-auto.

The osbuild-auto stage is used in automotive-image-builder to write
the aboot image to the "boot_a" partition, to allow android boot
systems to boot. We will want similar functionallity in
bootc-image-builder, so it is important to upstream this.

Signed-off-by: Alexander Larsson <alexl@redhat.com>

stages/org.osbuild.write-device

@@ -0,0 +1,49 @@
+#!/usr/bin/python3
+"""
+Write to device
+
+"""
+
+import fcntl
+import os
+import struct
+import subprocess
+import sys
+
+import osbuild.api
+from osbuild.util import parsing
+
+
+def blksize(device_path):
+    req = 0x80081272  # BLKGETSIZE64, result is bytes as unsigned 64-bit integer (uint64)
+    buf = b' ' * 8
+    fmt = 'L'
+
+    with open(device_path, "rb") as dev:
+        buf = fcntl.ioctl(dev.fileno(), req, buf)
+    return struct.unpack(fmt, buf)[0]
+
+
+def main(args, devices, options):
+    src = parsing.parse_location(options.get("from"), args)
+    device = devices["device"]["path"]
+
+    src_size = os.path.getsize(src)
+    print(f"src: '{src}' src_size: {src_size}")
+    device_size = blksize(device)
+    print(f"device: '{device}' device_size: {device_size}")
+    if src_size > device_size:
+        raise ValueError(
+            f"File too large ({src_size / (1024 * 1024):.1f} mb) for device ({device_size / (1024 * 1024):.1f} mb)")
+
+    cmd = ["dd", f"if={src}", f"of={device}", "status=progress", "conv=fsync"]
+    print("Running {cmd}")
+    subprocess.run(cmd, check=True)
+
+    return 0
+
+
+if __name__ == '__main__':
+    _args = osbuild.api.arguments()
+    r = main(_args, _args["devices"], _args["options"])
+    sys.exit(r)

stages/org.osbuild.write-device.meta.json

@@ -0,0 +1,39 @@
+{
+  "summary": "Write a file to a device",
+  "description": [
+    "This allows writing a file to a raw device. This is useful for example",
+    "to write bootloader or firmware files to custom partitions."
+  ],
+  "schema_2": {
+    "devices": {
+      "type": "object",
+      "additionalProperties": true,
+      "required": [
+        "device"
+      ],
+      "properties": {
+        "device": {
+          "type": "object",
+          "additionalProperties": true
+        }
+      }
+    },
+    "inputs": {
+      "type": "object",
+      "additionalProperties": true
+    },
+    "options": {
+      "additionalProperties": false,
+      "required": [
+        "from"
+      ],
+      "properties": {
+        "from": {
+          "type": "string",
+          "description": "The source",
+          "pattern": "^input:\\/\\/[^\\/]+\\/"
+        }
+      }
+    }
+  }
+}