[sonic_ssd] add ssd_emmc.py with EmmcUtil (sonic-net#362)

EmmcUtil class implements SsdBase API and can be used by ssdutil instead
of the default SsdUtil class on platforms that have eMMC.
The class is copied from Arista platform.

Signed-off-by: Yakiv Huryk <[email protected]>

sonic_platform_base/sonic_ssd/ssd_emmc.py

@@ -0,0 +1,51 @@
+#
+# ssd_emmc.py
+#
+# Implementation of SSD Utility API for eMMC.
+# It reads eMMC health, model, firmware, and serial from /sys/block/*.
+#
+
+try:
+    import os
+    from .ssd_base import SsdBase
+except ImportError as e:
+    raise ImportError(str(e) + "- required module not found")
+
+
+class EmmcUtil(SsdBase):
+    def __init__(self, diskdev):
+        self.diskdev = diskdev
+        self.path = os.path.join('/sys/block', os.path.basename(diskdev))
+
+    def _read_device_entry(self, entry, default=None):
+        path = os.path.join(self.path, 'device', entry)
+        try:
+            with open(path) as f:
+                return f.read().rstrip()
+        except OSError:
+            return default
+
+    def _is_slc(self):
+        return bool(self._read_device_entry('enhanced_area_offset'))
+
+    def get_health(self):
+        data = self._read_device_entry('life_time')
+        if data is None:
+            raise NotImplementedError
+        value = int(data.split()[0 if self._is_slc() else 1], 0)
+        return float(100 - (10 * (value - 1)))
+
+    def get_temperature(self):
+        return 'N/A'
+
+    def get_model(self):
+        return self._read_device_entry('name')
+
+    def get_firmware(self):
+        return self._read_device_entry('fwrev')
+
+    def get_serial(self):
+        return self._read_device_entry('serial')
+
+    def get_vendor_output(self):
+        return ''

tests/ssd_emmc_test.py

@@ -0,0 +1,40 @@
+import sys
+if sys.version_info.major == 3:
+    from unittest.mock import mock_open, patch
+else:
+    from mock import mock_open, patch
+
+from sonic_platform_base.sonic_ssd.ssd_emmc import EmmcUtil
+
+mocked_files = {
+    '/sys/block/emmctest/device/enhanced_area_offset': '0',
+    '/sys/block/emmctest/device/life_time': '0x02 0x02',
+    '/sys/block/emmctest/device/name': 'Test eMMC device',
+    '/sys/block/emmctest/device/fwrev': '0xAA00000000000000',
+    '/sys/block/emmctest/device/serial': '0xabcdefef'
+}
+
+
+def build_mocked_sys_fs_open(files):
+    mocks = dict([(fname, mock_open(read_data=cnt).return_value)
+                 for fname, cnt in files.items()])
+
+    def mopen(fname):
+        if fname in mocks:
+            return mocks[fname]
+        else:
+            raise FileNotFoundError(fname)
+    return mopen
+
+
+class TestSsdEMMC:
+
+    @patch('builtins.open', new=build_mocked_sys_fs_open(mocked_files))
+    def test_check(self, *args):
+        util = EmmcUtil('emmctest')
+
+        assert (util.get_health() == 90.0)
+        assert (util.get_temperature() == 'N/A')
+        assert (util.get_model() == 'Test eMMC device')
+        assert (util.get_firmware() == '0xAA00000000000000')
+        assert (util.get_serial() == '0xabcdefef')