[gearbox] Set context for phys based on configs (sonic-net#1826)

SAI_REDIS_SWITCH_ATTR_CONTEXT was set according to the phy_id
in gearbox_config.json. This change will set it based on the
context_id provided in that json file. The reason behind it is
to support the case of multiple phys sharing the same context.

gearsyncd/gearboxparser.cpp

@@ -143,6 +143,14 @@ bool GearboxParser::parse()
             val = phy["bus_id"];
             attr = std::make_pair("bus_id", std::to_string(val.get<int>()));
             attrs.push_back(attr);
+            if (phy.find("context_id") == phy.end())
+            {
+                SWSS_LOG_ERROR("missing 'context_id' field in 'phys' item %d in gearbox configuration", iter);
+                return false;
+            }
+            val = phy["context_id"];
+            attr = std::make_pair("context_id", std::to_string(val.get<int>()));
+            attrs.push_back(attr);
             if (phy.find("hwinfo") == phy.end())
             {
                 SWSS_LOG_ERROR("missing 'hwinfo' field in 'phys' item %d in gearbox configuration", iter);

lib/gearboxutils.cpp

@@ -185,6 +185,10 @@ std::map<int, gearbox_phy_t> GearboxUtils::loadPhyMap(Table *gearboxTable)
                 {
                     phy.bus_id = std::stoi(val.second);
                 }
+                else if (val.first == "context_id")
+                {
+                    phy.context_id = std::stoi(val.second);
+                }
             }
             gearboxPhyMap[phy.phy_id] = phy;
         }

lib/gearboxutils.h

@@ -44,6 +44,7 @@ typedef struct
     std::string hwinfo;
     uint32_t address;
     uint32_t bus_id;
+    uint32_t context_id;
 } gearbox_phy_t;
 
 typedef struct

orchagent/saihelper.cpp

@@ -418,7 +418,7 @@ sai_status_t initSaiPhyApi(swss::gearbox_phy_t *phy)
 
     /* Must be last Attribute */
     attr.id = SAI_REDIS_SWITCH_ATTR_CONTEXT;
-    attr.value.u64 = phy->phy_id;
+    attr.value.u64 = phy->context_id;
     attrs.push_back(attr);
 
     status = sai_switch_api->create_switch(&phyOid, (uint32_t)attrs.size(), attrs.data());