[Mellanox][pcied] Ignore bus on pcie.yaml for Mellanox switches (#8063)

Why I did it
BIOS upgrade on rare cases cannot guarantee bus value remain the same on every BIOS release. Ignoring this field in order for pcied not to fail but still verify device id in a different way. The solution is future proof and will not require changes in code when new BIOS version is available

How I did it
Since bus is not a fixed value (it is determined by the bios version) we are ignoring this field, and instead checking if there is a device that match on all other fields that and in addition has a matching device id.

How to verify it
Verify no errors or failures in pcied on different BIOS version with the same code base.

platform/mellanox/mlnx-platform-api/sonic_platform/pcie.py

@@ -0,0 +1,69 @@
+########################################################################
+#
+# Copyright (C) 2021, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+#
+# Module contains a platform specific implementation of SONiC Platform
+# Base PCIe class
+#
+########################################################################
+import os
+import re
+
+try:
+    from sonic_platform_base.sonic_pcie.pcie_common import PcieUtil
+except ImportError as e:
+    raise ImportError(str(e) + "- required module not found")
+
+SYSFS_PCI_DEVICE_PATH = '/sys/bus/pci/devices/'
+
+
+class Pcie(PcieUtil):
+    # check the current PCIe device with config file and return the result
+    # use bus from _device_id_to_bus_map instead of from yaml file
+    def get_pcie_check(self):
+        self.load_config_file()
+        for item_conf in self.confInfo:
+            id_conf = item_conf["id"]
+            dev_conf = item_conf["dev"]
+            fn_conf = item_conf["fn"]
+            bus_conf = self._device_id_to_bus_map.get(id_conf)
+            if bus_conf and self.check_pcie_sysfs(bus=int(bus_conf, base=16), device=int(dev_conf, base=16),
+                                                  func=int(fn_conf, base=16)):
+                item_conf["result"] = "Passed"
+            else:
+                item_conf["result"] = "Failed"
+        return self.confInfo
+
+    # Create
+    def _create_device_id_to_bus_map(self):
+        self._device_id_to_bus_map = {}
+        self.load_config_file()
+        device_folders = os.listdir(SYSFS_PCI_DEVICE_PATH)
+        for folder in device_folders:
+            # For each folder in the sysfs tree we check if it matches the normal PCIe device folder pattern,
+            # If match we add the device id from the device file and the bus from the folder name to the map
+            #
+            # Example for device folder name: 0000:ff:0b.1
+            #
+            # The folder name is built from:
+            #   4 hex digit of domain
+            #   colon ':'
+            #   2 hex digit of bus - this is what we are looking for
+            #   colon ':'
+            #   2 hex digit of id
+            #   dot '.'
+            #   1 digit of fn
+            pattern_for_device_folder = re.search('....:(..):..\..', folder)
+            if pattern_for_device_folder:
+                bus = pattern_for_device_folder.group(1)
+                with open(os.path.join('/sys/bus/pci/devices', folder, 'device'), 'r') as device_file:
+                    # The 'device' file contain an hex repesantaion of the id key in the yaml file.
+                    # Example of the file contact:
+                    # 0x6fe2
+                    # We will strip the new line character, and remove the 0x prefix that is not needed.
+                    device_id = device_file.read().strip().replace('0x', '')
+                    self._device_id_to_bus_map[device_id] = bus
+
+    def __init__(self, platform_path):
+        PcieUtil.__init__(self, platform_path)
+        self._create_device_id_to_bus_map()