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); "
-            "printf '%s\\n%s\\n%s\\n%s\\n%s\\n%s\\n' \"$v\" \"$n\" \"$r\" \"$s\" \"$u\" \"$d\""
+            "d=$(systemd-detect-virt 2>/dev/null); d=${d:-none}; "
+            "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 = (
@@ -292,13 +337,26 @@ class LinuxDriver(OSDriver):
             }
 
         # Bare-metal: prefer product_version when it reads like a marketing name
-        pv_usable = product_ver and product_ver != product_name and " " in product_ver
-        return {
-            "vendor": sys_vendor,
-            "model":  product_ver if pv_usable else product_name,
-            "serial": product_ser,
-            "is_vm":  False,
-        }
+        if sys_vendor or product_name:
+            pv_usable = product_ver and product_ver != product_name and " " in product_ver
+            return {
+                "vendor": sys_vendor,
+                "model":  product_ver if pv_usable else product_name,
+                "serial": product_ser,
+                "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."""