Doxygen comments for enum & structure

Added doxygen comments for enums & structures for user & channel
layers.

Unit-test:
verified build.

Change-Id: Ie5af8d6cdd4c04cb396869b7a3dc44f84efedd19
Signed-off-by: Richard Marian Thomaiyar <richard.marian.thomaiyar@linux.intel.com>
diff --git a/user_channel/channel_layer.hpp b/user_channel/channel_layer.hpp
index 3a9b5f5..60badbc 100644
--- a/user_channel/channel_layer.hpp
+++ b/user_channel/channel_layer.hpp
@@ -24,14 +24,19 @@
 static constexpr uint8_t maxIpmiChannels = 16;
 static constexpr uint8_t selfChNum = 0xE;
 
-// IPMI return codes specific to channel
+/**
+ * @enum IPMI return codes specific to channel (refer spec se 22.22 response
+ * data)
+ */
 enum ipmi_channel_return_codes
 {
     IPMI_CC_ACTION_NOT_SUPPORTED_FOR_CHANNEL = 0x82,
     IPMI_CC_ACCESS_MODE_NOT_SUPPORTED_FOR_CHANEL = 0x83
 };
 
-// IPMI Spec: Channel Protocol Type
+/**
+ * @enum Channel Protocol Type (refer spec sec 6.4)
+ */
 enum class EChannelProtocolType : uint8_t
 {
     na = 0x00,
@@ -47,7 +52,9 @@
     oem = 0x1C,
 };
 
-// IPMI Spec: Channel Medium Type
+/**
+ * @enum Channel Medium Type (refer spec sec 6.5)
+ */
 enum class EChannelMediumType : uint8_t
 {
     reserved = 0x00,
@@ -67,7 +74,10 @@
     unknown = 0x82,
 };
 
-// IPMI Spec: Channel Session Type
+/**
+ * @enum Channel Session Type (refer spec sec 22.24 -
+ * response data byte 5)
+ */
 enum class EChannelSessSupported : uint8_t
 {
     none = 0,
@@ -76,7 +86,9 @@
     any = 3,
 };
 
-// IPMI Spec: Channel Access Mode
+/**
+ * @enum Channel Access Mode (refer spec sec 6.6)
+ */
 enum class EChannelAccessMode : uint8_t
 {
     disabled = 0,
@@ -85,7 +97,10 @@
     shared = 3,
 };
 
-// IPMI Spec 2.0 : Authentication Types
+/**
+ * @enum Authentication Types (refer spec sec 13.6 - IPMI
+ * Session Header)
+ */
 enum class EAuthType : uint8_t
 {
     none = (1 << 0x0),
@@ -96,7 +111,10 @@
     oem = (1 << 0x5),
 };
 
-// IPMI Spec: Access mode for channel access set/get
+/**
+ * @enum Access mode for channel access set/get (refer spec
+ * sec 22.22 - request byte 2[7:6])
+ */
 typedef enum
 {
     doNotSet = 0x00,
@@ -105,6 +123,10 @@
     reserved = 0x03,
 } EChannelActionType;
 
+/**
+ * @enum Access set flag to determine changes that has to be updated
+ * in channel access data configuration.
+ */
 enum AccessSetFlag
 {
     setAccessMode = (1 << 0),
@@ -114,7 +136,12 @@
     setPrivLimit = (1 << 4),
 };
 
-// Struct to store channel access data
+/** @struct ChannelAccess
+ *
+ *  Structure to store channel access related information, defined in IPMI
+ * specification and used in Get / Set channel access (refer spec sec 22.22
+ * & 22.23)
+ */
 struct ChannelAccess
 {
     uint8_t accessMode;
@@ -124,7 +151,12 @@
     uint8_t privLimit;
 };
 
-// Struct store channel info data
+/** @struct ChannelInfo
+ *
+ *  Structure to store data about channel information, which identifies each
+ *  channel type and information as defined in IPMI specification. (refer spec
+ * sec 22.22 & 22.23)
+ */
 struct ChannelInfo
 {
     uint8_t mediumType;