Get Chassis Status should not bail if button interfaces are not present

The recent rewrite of Get Chassis Status also added support for reading
the front panel enables status instead of returning a hard-coded false.
But the implementation also errors out if the interface is not present
This makes the interfaces optional, returning false if they are not presnt
and reading them correctly if they are.

Tested-by: running ipmitool chassis status with and without the
           xyz.openbmc_project.Chassis.Buttons service running:

           # ipmitool chassis status
           System Power         : on
           Power Overload       : false
           Power Interlock      : inactive
           Main Power Fault     : false
           Power Control Fault  : false
           Power Restore Policy : previous
           Last Power Event     :
           Chassis Intrusion    : inactive
           Front-Panel Lockout  : inactive
           Drive Fault          : false
           Cooling/Fan Fault    : false
           Sleep Button Disable : not allowed
           Diag Button Disable  : not allowed
           Reset Button Disable : allowed
           Power Button Disable : allowed
           Sleep Button Disabled: false
           Diag Button Disabled : false
           Reset Button Disabled: false
           Power Button Disabled: false

           # systemctl stop xyz.openbmc_project.Chassis.Buttons@0.service

           # ipmitool chassis status
           System Power         : on
           Power Overload       : false
           Power Interlock      : inactive
           Main Power Fault     : false
           Power Control Fault  : false
           Power Restore Policy : previous
           Last Power Event     :
           Chassis Intrusion    : inactive
           Front-Panel Lockout  : inactive
           Drive Fault          : false
           Cooling/Fan Fault    : false
           Front Panel Control  : none

Change-Id: If845194b6f052ba84f8b062ac4259ec66f706bb5
Signed-off-by: Vernon Mauery <vernon.mauery@linux.intel.com>

1 files changed, 19 insertions, 8 deletions

diff --git a/chassishandler.cpp b/chassishandler.cpp
index dafc055..c9b39c0 100644
--- a/chassishandler.cpp
+++ b/chassishandler.cpp
@@ -936,17 +936,28 @@ ipmi::RspType<bool,    // Power is on
     }
 
     //  Front Panel Button Capabilities and disable/enable status(Optional)
-    std::optional<bool> powerButtonDisabled =
+    std::optional<bool> powerButtonReading =
         getButtonEnabled(powerButtonPath, powerButtonIntf);
-    constexpr bool powerButtonDisableAllow = true;
+    // allow disable if the interface is present
+    bool powerButtonDisableAllow = static_cast<bool>(powerButtonReading);
+    // default return the button is enabled (not disabled)
+    bool powerButtonDisabled = false;
+    if (powerButtonDisableAllow)
+    {
+        // return the real value of the button status, if present
+        powerButtonDisabled = *powerButtonReading;
+    }
 
-    std::optional<bool> resetButtonDisabled =
+    std::optional<bool> resetButtonReading =
         getButtonEnabled(resetButtonPath, resetButtonIntf);
-    constexpr bool resetButtonDisableAllow = true;
-
-    if (!powerButtonDisabled || !resetButtonDisabled)
+    // allow disable if the interface is present
+    bool resetButtonDisableAllow = static_cast<bool>(resetButtonReading);
+    // default return the button is enabled (not disabled)
+    bool resetButtonDisabled = false;
+    if (resetButtonDisableAllow)
     {
-        return ipmi::responseUnspecifiedError();
+        // return the real value of the button status, if present
+        resetButtonDisabled = *resetButtonReading;
     }
 
     // This response has a lot of hard-coded, unsupported fields
@@ -985,7 +996,7 @@ ipmi::RspType<bool,    // Power is on
         coolingFanFault, chassisIdentifyState, chassisIdentifySupport,
         false, // reserved
 
-        *powerButtonDisabled, *resetButtonDisabled, diagButtonDisabled,
+        powerButtonDisabled, resetButtonDisabled, diagButtonDisabled,
         sleepButtonDisabled, powerButtonDisableAllow, resetButtonDisableAllow,
         diagButtonDisableAllow, sleepButtonDisableAllow);
 }