Refactor ipmi::sensor::GetSensorResponse away from std::array

This change refactors GetSensorResponse from std::array to struct.
This change depends on change #23544.

GetSensorResponse is an internal, intermediate structure, an unpacked
form of a Get Sensor Reading response, providing direct access to its
fields. Its life time is:
GetReadingResponse -> GetSensorResponse -> ipmi::RspType.

It is written to in 5 functions in the ipmi::sensor::get namespace, by
four setter functions (setOffset, setReading, setAssertionBytes,
enableScanning).
It is currently read from by 1 function (ipmiSensorGetSensorReading)
for transforming to an ipmi::RspType.

Originally, the setter functions assumed bitwise equivalence between
GetSensorResponse and GetReadingResponse, and the setter functions
used reinterpret_cast to assign to a GetSensorResponse as if it were
a GetReadingResponse.

With this change, the reinterpret_cast's are removed, and the set
functions now accept GetSensorResponse instead of GetReadingResponse,
so the code gets a bit easier to read.

Tested: Tested using a server with a BMC; sensor readings obtained
through `ipmitool` appear to be correct (the reading might change
within a small range):
 # ipmitool raw 0x04 0x2d 0x16
   9B 40 00 00

Signed-off-by: Sui Chen <suichen@google.com>
Change-Id: I5d454d6249f5431fb98169e6ef7c585c34024004

1 files changed, 9 insertions, 1 deletions

diff --git a/include/ipmid/types.hpp b/include/ipmid/types.hpp
index e2f80c0..3e64cb4 100644
--- a/include/ipmid/types.hpp
+++ b/include/ipmid/types.hpp
@@ -100,7 +100,15 @@ struct GetReadingResponse
 
 constexpr auto inventoryRoot = "/xyz/openbmc_project/inventory";
 
-using GetSensorResponse = std::array<uint8_t, sizeof(GetReadingResponse)>;
+struct GetSensorResponse
+{
+    uint8_t reading;                     // sensor reading
+    bool readingOrStateUnavailable;      // 1 = reading/state unavailable
+    bool scanningEnabled;                // 0 = sensor scanning disabled
+    bool allEventMessagesEnabled;        // 0 = All Event Messages disabled
+    uint8_t thresholdLevelsStates;       // threshold/discrete sensor states
+    uint8_t discreteReadingSensorStates; // discrete-only, optional states
+};
 
 using OffsetValueMap = std::map<Offset, Values>;