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+.. _OPAL_SENSOR_READ:
+
+OPAL_SENSOR_READ
+================
+
+.. code-block:: c
+
+   #define OPAL_SENSOR_READ			88
+
+   int64_t opal_sensor_read(uint32_t sensor_hndl, int token, uint32_t *sensor_data);
+
+The OPAL sensor call reads a sensor data using a unique handler to
+identity the targeted sensor. The `sensor_handle` is provided
+via the device tree and is opaque to the OS (although we currently
+do use an encoding scheme).
+
+This call can be asynchronous, when a message needs to be sent to a
+service processor for example.  In this case, the call will return
+OPAL_ASYNC_COMPLETION and the token parameter will be used to wait for
+the completion of the request.
+
+The OPAL API doesn't enforce alimit on the number of sensor calls that can
+be in flight.
+
+Internally, :ref:`OPAL_SENSOR_READ` is implemented as a wrapper around
+:ref:`OPAL_SENSOR_READ_U64`. Any code targeting processor generations prior
+to POWER9 will need to use :ref:`OPAL_CHECK_TOKEN` to ensure :ref:`OPAL_SENSOR_READ_U64`
+is present and gracefully fall back to :ref:`OPAL_SENSOR_READ` if it is not.
+
+Parameters
+----------
+::
+
+	uint32_t sensor_handle
+	int	 token
+	uint32_t *sensor_data
+
+
+Return values
+-------------
+:ref:`OPAL_SUCCESS`
+  Success!
+:ref:`OPAL_PARAMETER`
+  invalid sensor handle
+:ref:`OPAL_UNSUPPORTED`
+  platform does not support reading sensors.
+:ref:`OPAL_ASYNC_COMPLETION`
+  a request was sent and an async completion will
+  be triggered with the @token argument
+:ref:`OPAL_PARTIAL`
+  the request completed but the data returned is invalid
+:ref:`OPAL_BUSY_EVENT`
+  a previous request is still pending
+:ref:`OPAL_NO_MEM`
+  allocation failed
+:ref:`OPAL_INTERNAL_ERROR`
+  communication failure with the FSP
+:ref:`OPAL_HARDWARE`
+  FSP is not available
+
+.. _OPAL_SENSOR_READ_U64:
+
+OPAL_SENSOR_READ_U64
+====================
+
+.. code-block:: c
+
+   #define OPAL_SENSOR_READ_U64			162
+
+   s64 opal_sensor_read_u64(u32 sensor_hndl, int token, u64 *sensor_data);
+
+The OPAL sensor call to read sensor data of type u64. Unlike
+opal_sensor_read which reads upto u32 this call can be used to
+read values of sensors upto 64bits. The calling conventions and
+return values are same as :ref:`OPAL_SENSOR_READ`.
+
+All sensors can be read through the :ref:`OPAL_SENSOR_READ_U64` call that
+can be read using the :ref:`OPAL_SENSOR_READ` call. Internally,
+:ref:`OPAL_SENSOR_READ` is a wrapper around :ref:`OPAL_SENSOR_READ_U64`.
+Any code targeting processor generations prior to POWER9 will need to use
+:ref:`OPAL_CHECK_TOKEN` to ensure :ref:`OPAL_SENSOR_READ_U64`
+is present and gracefully fall back to :ref:`OPAL_SENSOR_READ` if it is not.