Add new config option for new MSI laptops with absolute down threshold storage

Some new MSI laptops released starting circa 2025 appear to be storing absolute temperature down thresholds (instead of offsets from the up thresholds), resulting in odd down threshold display in YAMDCC configs and editor.

Author: Sparronator9999

YAMDCC.Common/Configs/YAMDCC_Config.cs

@@ -88,6 +88,18 @@ public sealed class YAMDCC_Config
     [XmlElement]
     public DateTime? FirmDate { get; set; }
 
+    /// <summary>
+    /// Set to <see langword="true"/> if the temperature down thresholds are
+    /// stored in the EC as an offset from the corresponding up threshold,
+    /// otherwise <see langword="false"/>.
+    /// </summary>
+    /// <remarks>
+    /// Only known to be needed for one MSI laptop so far
+    /// (Vector 16 HX AI A2XWIG), and possibly more released in 2025 or later.
+    /// </remarks>
+    [XmlElement]
+    public bool OffsetDT { get; set; } = true;
+
     /// <summary>
     /// The list of <see cref="FanConf"/>s associated with the laptop.
     /// </summary>

YAMDCC.Service/FanControlService.cs

@@ -577,7 +577,11 @@ private bool ApplyConf()
                     {
                         success = false;
                     }
-                    if (!LogECWriteByte(cfg.DownThresholdRegs[j - 1], (byte)(t.UpThreshold - t.DownThreshold)))
+                    byte downT = Config.OffsetDT
+                        ? (byte)(t.UpThreshold - t.DownThreshold)
+                        : t.DownThreshold;
+
+                    if (!LogECWriteByte(cfg.DownThresholdRegs[j - 1], downT))
                     {
                         success = false;
                     }
@@ -924,7 +928,9 @@ private bool ECtoConf()
                         }
                         if (LogECReadByte(cfg.DownThresholdRegs[j - 1], out value))
                         {
-                            t.DownThreshold = (byte)(t.UpThreshold - value);
+                            t.DownThreshold = Config.OffsetDT
+                                ? (byte)(t.UpThreshold - value)
+                                : value;
                         }
                     }
                 }