Create additional option to setup FS geometry

Some platforms like the TI AM62 require a particular FAT geometry for
their CPU to read the file system (and thus the bootloader). Failing
that the CPU will simply not boot and keep looking for a bootloader.

Let's add some options to enforce a particular filesystem geometry
through the -g option of mkfs.fat.

Signed-off-by: Maxime Ripard <mripard@kernel.org>

stages/org.osbuild.mkfs.fat

@@ -46,6 +46,22 @@ SCHEMA_2 = r"""
       "description": "Label for the file system",
         "type": "integer",
         "enum": [12, 16, 32]
+    },
+    "geometry": {
+      "description": "Disk Geometry for the file system",
+      "type": "object",
+      "additionalProperties": false,
+      "required": ["heads", "sectors-per-track"],
+      "properties": {
+        "heads": {
+          "description": "Number of Heads",
+          "type": "integer"
+        },
+        "sectors-per-track": {
+          "description": "Number of Sectors per Track",
+          "type": "integer"
+        }
+      }
     }
   }
 }
@@ -58,6 +74,7 @@ def main(devices, options):
     volid = options["volid"]
     label = options.get("label")
     fatsize = options.get("fat-size")
+    geometry = options.get("geometry")
     opts = ["mkfs.fat", "-I", "-i", volid]
 
     if label:
@@ -66,6 +83,9 @@ def main(devices, options):
     if fatsize:
         opts += ["-F", str(fatsize)]
 
+    if geometry:
+        opts += ["-g", f"{geometry['heads']}/{geometry['sectors-per-track']}"]
+
     subprocess.run(opts + [device], encoding='utf8', check=True)
 
 

test/data/stages/fat/manifest.json

@@ -0,0 +1,41 @@
+{
+  "version": "2",
+  "pipelines": [
+    {
+      "name": "image",
+      "stages": [
+        {
+          "type": "org.osbuild.truncate",
+          "options": {
+            "filename": "disk.img",
+            "size": "64M"
+          }
+        },
+        {
+          "type": "org.osbuild.mkfs.fat",
+          "options": {
+            "volid": "7B7795E7",
+            "geometry": {
+              "heads": 12,
+              "sectors-per-track": 42
+            }
+          },
+          "devices": {
+            "device": {
+              "type": "org.osbuild.loopback",
+              "options": {
+                "filename": "disk.img",
+                "lock": true
+              }
+            }
+          }
+        }
+      ]
+    }
+  ],
+  "sources": {
+    "org.osbuild.curl": {
+      "items": {}
+    }
+  }
+}

test/data/stages/fat/manifest.mpp.yaml

@@ -0,0 +1,20 @@
+version: '2'
+pipelines:
+  - name: image
+    stages:
+      - type: org.osbuild.truncate
+        options:
+          filename: disk.img
+          size: '64M'
+      - type: org.osbuild.mkfs.fat
+        options:
+          volid: 7B7795E7
+          geometry:
+            heads: 12
+            sectors-per-track: 42
+        devices:
+          device:
+            type: org.osbuild.loopback
+            options:
+              filename: disk.img
+              lock: true

test/run/test_stages.py

@@ -16,7 +16,7 @@ import tempfile
 import unittest
 import xml
 from collections.abc import Mapping
-from typing import Callable, Dict, Optional
+from typing import Callable, Dict, List, Optional
 
 from osbuild.util import checksum, selinux
 from .test_assemblers import mount
@@ -595,3 +595,49 @@ class TestStages(test.TestBase):
                 assert len(subvols) == 2
                 assert "path root" in subvols[0]
                 assert "path home" in subvols[1]
+
+    @unittest.skipUnless(test.TestBase.has_filesystem_support("fat"), "FAT needed")
+    def test_fat(self):
+        def _get_file_fields(image: str) -> List[str]:
+            r = subprocess.run(
+                [
+                    "file",
+                    "--special-files",
+                    image
+                ],
+                stdout=subprocess.PIPE,
+                stderr=subprocess.PIPE,
+                encoding="utf8",
+                check=True,
+            )
+
+            return [field.strip() for field in r.stdout.split(',')]
+
+        datadir = self.locate_test_data()
+        testdir = os.path.join(datadir, "stages", "fat")
+
+        with self.osbuild as osb, tempfile.TemporaryDirectory(dir="/var/tmp") as outdir:
+            osb.compile_file(os.path.join(testdir, "manifest.json"), exports=["image"], output_dir=outdir)
+
+            image = os.path.join(outdir, "image", "disk.img")
+            assert os.path.isfile(image)
+
+            # check that it's indeed FAT
+            r = subprocess.run(
+                [
+                    "blkid",
+                    "--output", "export",
+                    image
+                ],
+                stdout=subprocess.PIPE,
+                stderr=subprocess.PIPE,
+                encoding="utf8",
+                check=True,
+            )
+
+            assert "TYPE=vfat" in r.stdout.splitlines()
+
+            # Check that our custom geometry was enforced
+            fields = _get_file_fields(image)
+            assert "heads 12" in fields
+            assert "sectors/track 42" in fields