feat: ARM hardware detection via device tree and /proc/cpuinfo

On ARM boards (Raspberry Pi, ODROID, etc.) /sys/class/dmi/id/ does not
exist. _collect_platform_info() now falls back to:
  - /sys/firmware/devicetree/base/model  (preferred)
  - /proc/cpuinfo Model: / Serial:       (fallback)

Three bugs fixed in the process:

1. systemd-detect-virt exits 1 on bare metal, so the old
   "|| echo none" pattern produced d="none\nnone" (two lines),
   shifting all subsequent fields by one. Fixed with ${d:-none}.

2. _send() calls .strip() on output, silently eating the five leading
   blank lines that represent empty DMI fields on ARM. Fixed by
   prefixing the printf output with a DMIBEGIN sentinel so the parser
   can locate field 0 regardless of leading whitespace.

3. Vendor was always empty for ARM, falling back to the generic "Linux"
   constant. Added _ARM_VENDOR_PREFIXES lookup table and
   _arm_vendor_from_model() to derive the canonical vendor name from
   the model string (e.g. "Raspberry Pi Foundation" for any RPi board).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

napalm_linux/linux.py

@@ -85,6 +85,36 @@ _VM_DMI_VENDORS: frozenset[str] = frozenset({
     "parallels software international inc.",
 })
 
+# Known ARM board model prefixes → canonical vendor name
+_ARM_VENDOR_PREFIXES: list[tuple[str, str]] = [
+    ("Raspberry Pi",    "Raspberry Pi Foundation"),
+    ("NVIDIA Jetson",   "NVIDIA"),
+    ("ODROID",          "Hardkernel"),
+    ("Hardkernel",      "Hardkernel"),
+    ("Rock Pi",         "Radxa"),
+    ("ROCK Pi",         "Radxa"),
+    ("Radxa",           "Radxa"),
+    ("Orange Pi",       "Xunlong Software"),
+    ("Banana Pi",       "SinoVoip"),
+    ("NanoPi",          "FriendlyElec"),
+    ("PINE64",          "Pine64"),
+    ("BeagleBone",      "BeagleBoard.org"),
+]
+
+
+def _arm_vendor_from_model(model: str) -> str:
+    """Extract vendor from an ARM device tree / cpuinfo model string."""
+    for prefix, vendor in _ARM_VENDOR_PREFIXES:
+        if model.startswith(prefix):
+            return vendor
+    # Generic fallback: words before the first numeric token
+    brand = []
+    for word in model.split():
+        if word[0].isdigit():
+            break
+        brand.append(word)
+    return " ".join(brand)
+
 
 class LinuxDriver(OSDriver):
     """NAPALM driver for generic Linux systems.
@@ -235,11 +265,23 @@ class LinuxDriver(OSDriver):
             "r=$(cat /sys/class/dmi/id/product_version 2>/dev/null); "
             "s=$(cat /sys/class/dmi/id/product_serial 2>/dev/null); "
             "u=$(cat /sys/class/dmi/id/product_uuid 2>/dev/null); "
-            "d=$(systemd-detect-virt 2>/dev/null || echo none); "
+            "d=$(systemd-detect-virt 2>/dev/null); d=${d:-none}; "
-            "printf '%s\\n%s\\n%s\\n%s\\n%s\\n%s\\n' \"$v\" \"$n\" \"$r\" \"$s\" \"$u\" \"$d\""
+            "dt=$(tr -d '\\0' </sys/firmware/devicetree/base/model 2>/dev/null); "
+            "cs=$(grep '^Serial' /proc/cpuinfo 2>/dev/null | head -1 | cut -d: -f2 | xargs 2>/dev/null); "
+            "cm=$(grep '^Model' /proc/cpuinfo 2>/dev/null | head -1 | cut -d: -f2 | xargs 2>/dev/null); "
+            # DMIBEGIN sentinel: _send() strips leading blank lines (ARM has no DMI
+            # files, so fields 0-4 are empty). The sentinel anchors the output so
+            # splitlines()[start+N] always maps to the correct field index.
+            "printf 'DMIBEGIN\\n%s\\n%s\\n%s\\n%s\\n%s\\n%s\\n%s\\n%s\\n%s\\n' "
+            "\"$v\" \"$n\" \"$r\" \"$s\" \"$u\" \"$d\" \"$dt\" \"$cs\" \"$cm\""
         )
         try:
-            lines = self._send(dmi_cmd).splitlines()
+            raw_lines = self._send(dmi_cmd).splitlines()
+            try:
+                start = raw_lines.index("DMIBEGIN") + 1
+            except ValueError:
+                start = 0
+            lines = raw_lines[start:]
         except Exception:
             return {"vendor": "", "model": "", "serial": "", "is_vm": False}
 
@@ -253,6 +295,9 @@ class LinuxDriver(OSDriver):
         product_ser   = _clean(3)
         product_uuid  = _clean(4)
         detect_virt   = lines[5].strip().lower() if len(lines) > 5 else "none"
+        dt_model      = _clean(6)
+        cpuinfo_ser   = _clean(7)
+        cpuinfo_mdl   = _clean(8)
 
         is_container = detect_virt in _CONTAINER_VIRT
         is_vm = (
@@ -292,6 +337,7 @@ class LinuxDriver(OSDriver):
             }
 
         # Bare-metal: prefer product_version when it reads like a marketing name
+        if sys_vendor or product_name:
             pv_usable = product_ver and product_ver != product_name and " " in product_ver
             return {
                 "vendor": sys_vendor,
@@ -300,6 +346,18 @@ class LinuxDriver(OSDriver):
                 "is_vm":  False,
             }
 
+        # ARM/embedded fallback: no DMI, try device tree and /proc/cpuinfo
+        arm_model = dt_model or cpuinfo_mdl
+        if arm_model:
+            return {
+                "vendor": _arm_vendor_from_model(arm_model),
+                "model":  arm_model,
+                "serial": cpuinfo_ser,
+                "is_vm":  False,
+            }
+
+        return {"vendor": "", "model": "", "serial": "", "is_vm": False}
+
     def get_facts(self) -> dict[str, Any]:
         """Return basic system facts."""
         hostname = self._send("hostname -s 2>/dev/null || hostname")

tests/test_linux.py

@@ -2,7 +2,7 @@
 
 import pytest
 from unittest.mock import MagicMock, patch
-from napalm_linux.linux import LinuxDriver
+from napalm_linux.linux import LinuxDriver, _arm_vendor_from_model
 
 
 # ---------------------------------------------------------------------------
@@ -368,8 +368,18 @@ def _dmi_output(
     product_serial: str,
     product_uuid: str,
     detect_virt: str,
+    dt_model: str = "",
+    cpuinfo_serial: str = "",
+    cpuinfo_model: str = "",
 ) -> str:
-    return "\n".join([sys_vendor, product_name, product_version, product_serial, product_uuid, detect_virt])
+    # Mirrors the real shell output: DMIBEGIN sentinel followed by 9 fields.
+    # The sentinel prevents _send()'s .strip() from eating leading blank lines
+    # (which occur on ARM where all DMI files are absent).
+    return "\n".join([
+        "DMIBEGIN",
+        sys_vendor, product_name, product_version, product_serial,
+        product_uuid, detect_virt, dt_model, cpuinfo_serial, cpuinfo_model,
+    ])
 
 
 class TestCollectPlatformInfo:
@@ -482,6 +492,95 @@ class TestCollectPlatformInfo:
         assert info["model"] == ""
         assert info["is_vm"] is False
 
+    def test_arm_device_tree_fallback(self, driver):
+        raw = _dmi_output(
+            "", "", "", "", "", "none",
+            dt_model="Raspberry Pi 4 Model B Rev 1.4",
+            cpuinfo_serial="100000002a6d96dc",
+            cpuinfo_model="Raspberry Pi 4 Model B Rev 1.4",
+        )
+        with patch.object(driver, "_send", return_value=raw):
+            info = driver._collect_platform_info()
+        assert info["vendor"] == "Raspberry Pi Foundation"
+        assert info["model"] == "Raspberry Pi 4 Model B Rev 1.4"
+        assert info["serial"] == "100000002a6d96dc"
+        assert info["is_vm"] is False
+
+    def test_arm_cpuinfo_model_when_no_dt(self, driver):
+        raw = _dmi_output(
+            "", "", "", "", "", "none",
+            dt_model="",
+            cpuinfo_serial="0000000012345678",
+            cpuinfo_model="Raspberry Pi 3 Model B Plus Rev 1.3",
+        )
+        with patch.object(driver, "_send", return_value=raw):
+            info = driver._collect_platform_info()
+        assert info["vendor"] == "Raspberry Pi Foundation"
+        assert info["model"] == "Raspberry Pi 3 Model B Plus Rev 1.3"
+        assert info["serial"] == "0000000012345678"
+        assert info["is_vm"] is False
+
+    def test_arm_no_fallback_data_returns_empty(self, driver):
+        raw = _dmi_output("", "", "", "", "", "none")
+        with patch.object(driver, "_send", return_value=raw):
+            info = driver._collect_platform_info()
+        assert info["vendor"] == ""
+        assert info["model"] == ""
+        assert info["is_vm"] is False
+
+    def test_bare_metal_detect_virt_exit1_does_not_shift_arm_fields(self, driver):
+        # systemd-detect-virt exits 1 on bare metal, old "|| echo none" caused
+        # d="none\nnone" which shifted subsequent lines off by one.
+        # With the ${d:-none} fix this no longer happens.
+        raw = _dmi_output(
+            "", "", "", "", "", "none",
+            dt_model="",
+            cpuinfo_serial="0000000012345678",
+            cpuinfo_model="Raspberry Pi 3 Model B Rev 1.2",
+        )
+        with patch.object(driver, "_send", return_value=raw):
+            info = driver._collect_platform_info()
+        assert info["vendor"] == "Raspberry Pi Foundation"
+        assert info["model"] == "Raspberry Pi 3 Model B Rev 1.2"
+        assert info["serial"] == "0000000012345678"
+
+    def test_arm_fallback_ignored_when_dmi_present(self, driver):
+        raw = _dmi_output(
+            "Dell Inc.", "PowerEdge R720", "Not Specified", "XYZ999",
+            "8a2e3f00-dead-beef-0000-123456789abc", "none",
+            dt_model="some-dt-model",
+            cpuinfo_serial="deadbeef",
+            cpuinfo_model="some cpuinfo model",
+        )
+        with patch.object(driver, "_send", return_value=raw):
+            info = driver._collect_platform_info()
+        assert info["vendor"] == "Dell Inc."
+        assert info["model"] == "PowerEdge R720"
+        assert info["serial"] == "XYZ999"
+
+
+# ---------------------------------------------------------------------------
+# _arm_vendor_from_model
+# ---------------------------------------------------------------------------
+
+
+@pytest.mark.parametrize("model,expected", [
+    ("Raspberry Pi 4 Model B Rev 1.4",     "Raspberry Pi Foundation"),
+    ("Raspberry Pi 3 Model B Rev 1.2",     "Raspberry Pi Foundation"),
+    ("ODROID-N2L",                          "Hardkernel"),
+    ("NVIDIA Jetson Nano Developer Kit",    "NVIDIA"),
+    ("Rock Pi 4C",                          "Radxa"),
+    ("Orange Pi 5 Plus",                    "Xunlong Software"),
+    ("Banana Pi BPI-R3",                    "SinoVoip"),
+    ("NanoPi R4S",                          "FriendlyElec"),
+    ("PINE64 RockPro64",                    "Pine64"),
+    ("BeagleBone Black",                    "BeagleBoard.org"),
+    ("Unknown Board 1.0",                   "Unknown Board"),
+    ("SomeSingleWordBoard",                 "SomeSingleWordBoard"),
+])
+def test_arm_vendor_from_model(model, expected):
+    assert _arm_vendor_from_model(model) == expected
+
 
 # ---------------------------------------------------------------------------
 # get_facts uses _collect_platform_info