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+### phosphor-nvme
+
+#### Introduction
+
+phosphor-nvme is the nvme manager service maintains for NVMe drive information
+update and related notification processing service. The service update
+information to `xyz/openbmc_project/Nvme/Status.interface.yaml`,
+`xyz/openbmc_project/Sensor/Value.interface.yaml` and
+other interfaces in `xyz.openbmc_project.Inventory.Manager`.
+
+#### General usage
+
+The service `xyz.openbmc_project.nvme.manager` provides object on D-Bus:
+
+* /xyz/openbmc_project/sensors/temperature/nvme(index)
+
+where object implements interface `xyz.openbmc_project.Sensor.Value`.
+
+NVMe drive export as sensor and sensor value is temperature of drive.
+It can get the sensor value of the drive through ipmitool command `sdr elist`
+if the corresponding settings in the sensor map are configured correctly.
+For example:
+
+* To get sensor value:
+
+   ```
+   ### With ipmi command on BMC
+   ipmitool sdr elist
+   ```
+
+The service also updates other NVMe drive information to D-bus
+`xyz.openbmc_project.Inventory.Manager`. The service
+`xyz.openbmc_project.Inventory.Manager` provides object on D-Bus:
+
+* /xyz/openbmc_project/inventory/system/chassis/motherboard/nvme(index)
+
+where object implements interfaces:
+
+* xyz.openbmc_project.Inventory.Item
+* xyz.openbmc_project.Inventory.Decorator.Asset
+* xyz.openbmc_project.Nvme.Status
+
+Interface `xyz.openbmc_project.Nvme.Status` with the following properties:
+
+| Property | Type | Description |
+| -------- | ---- | ----------- |
+| SmartWarnings| string | Indicates smart warnings for the state |
+| StatusFlags | string | Indicates the status of the drives |
+| DriveLifeUsed | string | A vendor specific estimate of the percentage |
+| TemperatureFault| bool | If warning type about temperature happened |
+| BackupdrivesFault | bool | If warning type about backup drives happened |
+| CapacityFault| bool | If warning type about capacity happened |
+| DegradesFault| bool | If warning type about degrades happened |
+| MediaFault| bool | If warning type about media happened |
+
+Interface `xyz.openbmc_project.Inventory.Item` with the following properties:
+
+| Property | Type | Description |
+| -------- | ---- | ----------- |
+| Present | bool | Whether or not the item is present |
+
+Interface `xyz.openbmc_project.Inventory.Decorator.Asset` with the following
+properties:
+
+| Property | Type | Description |
+| -------- | ---- | ----------- |
+| SerialNumber | string | The item serial number |
+| Manufacturer | string | The item manufacturer |
+
+Each property in the inventory manager can be obtained via the busctl
+get-property command. For example:
+
+* To get property Present:
+
+   ```
+   ### With busctl on BMC
+   busctl get-property xyz.openbmc_project.Inventory.Manager /xyz/openbmc_project/inventory/system/chassis/motherboard/nvme0 xyz.openbmc_project.Inventory.Item Present
+   ```
+
+#### Configuration file
+
+There is a JSON configuration file `nvme_config.json` for drive index, bus ID,
+and the LED object path and bus name for each drive.
+For example,
+
+```json
+{
+    "config": [
+        {
+            "NVMeDriveIndex": 0,
+            "NVMeDriveBusID": 16,
+            "NVMeDriveFaultLEDGroupPath": "/xyz/openbmc_project/led/groups/led_u2_0_fault",
+            "NVMeDriveLocateLEDGroupPath": "/xyz/openbmc_project/led/groups/led_u2_0_locate",
+            "NVMeDriveLocateLEDControllerBusName":"xyz.openbmc_project.LED.Controller.led_u2_0_locate",
+            "NVMeDriveLocateLEDControllerPath":"/xyz/openbmc_project/led/physical/led_u2_0_locate",
+            "NVMeDrivePresentPin": 148,
+            "NVMeDrivePwrGoodPin": 161
+        },
+        {
+            "NVMeDriveIndex": 1,
+            "NVMeDriveBusID": 17,
+            "NVMeDriveFaultLEDGroupPath": "/xyz/openbmc_project/led/groups/led_u2_1_fault",
+            "NVMeDriveLocateLEDGroupPath": "/xyz/openbmc_project/led/groups/led_u2_1_locate",
+            "NVMeDriveLocateLEDControllerBusName":"xyz.openbmc_project.LED.Controller.led_u2_1_locate",
+            "NVMeDriveLocateLEDControllerPath":"/xyz/openbmc_project/led/physical/led_u2_1_locate",
+            "NVMeDrivePresentPin": 149,
+            "NVMeDrivePwrGoodPin": 162
+        }
+    ],
+    "threshold":[
+        {
+            "criticalHigh":70,
+            "criticalLow":0,
+            "maxValue":70,
+            "minValue":0
+        }
+    ]
+}
+```
+
+* config
+  * NvmeDriveIndex: The index of the NVMe drive, which will be displayed in the
+                    object path.
+  * NVMeDriveBusID: The bus id of the NVMe drive, since it communicates with SMBus.
+  * NVMeDriveFaultLEDGroupPath: Object path of fault LED  in LED Group Manager.
+  * NVMeDriveLocateLEDGroupPath: Object path of locate LED  in LED Group Manager.
+  * NVMeDriveLocateLEDControllerBusName: D-Bus name of locate LED in LED Controller.
+  * NVMeDriveLocateLEDControllerPath: Object path of locate LED in LED Controller.
+  * NVMeDrivePresentPin: Gpio present pin of NVMe drive.
+  * NVMeDrivePwrGoodPin: Gpio Power good pin of NVMe drive.
+* threshold
+  * criticalHigh: Upper critical threshold.
+  * criticalLow: Lower critical threshold.
+  * maxValue: Sensor maximum value.
+  * minValue: Sensor value.
+
+#### Process
+
+1. It will register a D-bus called `xyz.openbmc_project.nvme.manager`
+   description above.
+2. Obtain the drive index, bus ID, GPIO present pin, power good pin and fault
+   LED object path from the json file mentioned above.
+3. Each cycle will do following steps:
+   1. Check if the present pin of target drive is true, if true, means drive
+      exists and go to next step. If not, means drive does not exists and
+      remove object path from D-bus by drive index.
+   2. Check if the power good pin of target drive is true, if true means drive
+      is ready then create object path by drive index and go to next step. If
+      not, means drive power abnormal, turn on fault LED and log in journal.
+   3. Send a NVMe-MI command via SMBus Block Read protocol by bus ID of target
+      drive to get data. Data get from NVMe drives are "Status Flags",
+      "SMART Warnings", "Temperature", "Percentage Drive Life Used",
+      "Vendor ID", and "Serial Number".
+   4. The data will be set to the properties in D-bus.
+
+This service will run automatically and look up NVMe drives every second.