[CMBATT] Convert power statistics from mAh to mWh

ReactOS (like any other OSes) expects power data to be represented in milliwatts per hour, not in milliamps per hour.
Currently CMBATT defaults the stats to unknown values, if that's the case, and there are a bunch of machines that do report their data from _BIF ACPI method in ampere.

CORE-18969
CORE-19452

drivers/bus/acpi/cmbatt/cmbatt.c

@@ -275,10 +275,12 @@ CmBattUnload(IN PDRIVER_OBJECT DriverObject)
 
 NTSTATUS
 NTAPI
-CmBattVerifyStaticInfo(PCMBATT_DEVICE_EXTENSION DeviceExtension,
-                       ULONG BatteryTag)
+CmBattVerifyStaticInfo(
+    _Inout_ PCMBATT_DEVICE_EXTENSION DeviceExtension,
+    _In_ ULONG BatteryTag)
 {
     ACPI_BIF_DATA BifData;
+    ULONG DesignVoltage = DeviceExtension->BifData.DesignVoltage;
     PBATTERY_INFORMATION Info = &DeviceExtension->BatteryInformation;
     NTSTATUS Status;
 
@@ -292,16 +294,44 @@ CmBattVerifyStaticInfo(PCMBATT_DEVICE_EXTENSION DeviceExtension,
         // FIXME: take from _BIX method: Info->CycleCount
         DeviceExtension->BifData = BifData;
 
-        if (BifData.PowerUnit == 1)
+        /* Check if the power stats are reported in ampere or watts */
+        if (BifData.PowerUnit == ACPI_BATT_POWER_UNIT_AMPS)
         {
-            DPRINT1("FIXME: need to convert mAh into mWh\n");
-            Info->DesignedCapacity = BATTERY_UNKNOWN_CAPACITY;
-            Info->FullChargedCapacity = BATTERY_UNKNOWN_CAPACITY;
-            Info->DefaultAlert1 = BATTERY_UNKNOWN_CAPACITY;
-            Info->DefaultAlert2 = BATTERY_UNKNOWN_CAPACITY;
+            /*
+             * We have got power stats in milli-ampere but ReactOS expects the values
+             * to be reported in milli-watts, so we have to convert them.
+             * In order to do so we must expect the design voltage of the battery
+             * is not unknown.
+             */
+            if ((DesignVoltage != BATTERY_UNKNOWN_VOLTAGE) && (DesignVoltage != 0))
+            {
+                /* Convert the design capacity */
+                Info->DesignedCapacity = CONVERT_BATT_INFO(BifData.DesignCapacity, DesignVoltage);
+
+                /* Convert the full charged capacity */
+                Info->FullChargedCapacity = CONVERT_BATT_INFO(BifData.LastFullCapacity, DesignVoltage);
+
+                /* Convert the low capacity alarm (DefaultAlert1) */
+                Info->DefaultAlert1 = CONVERT_BATT_INFO(BifData.DesignCapacityLow, DesignVoltage);
+
+                /* Convert the designed capacity warning alarm (DefaultAlert2) */
+                Info->DefaultAlert2 = CONVERT_BATT_INFO(BifData.DesignCapacityWarning, DesignVoltage);
+            }
+            else
+            {
+                /*
+                 * Without knowing the nominal designed voltage of the battery
+                 * we cannot determine the power consumption of this battery.
+                 */
+                Info->DesignedCapacity = BATTERY_UNKNOWN_CAPACITY;
+                Info->FullChargedCapacity = BATTERY_UNKNOWN_CAPACITY;
+                Info->DefaultAlert1 = BATTERY_UNKNOWN_CAPACITY;
+                Info->DefaultAlert2 = BATTERY_UNKNOWN_CAPACITY;
+            }
         }
         else
         {
+            /* The stats are in milli-watts, use them directly */
             Info->DesignedCapacity = BifData.DesignCapacity;
             Info->FullChargedCapacity = BifData.LastFullCapacity;
             Info->DefaultAlert1 = BifData.DesignCapacityLow;
@@ -939,7 +969,7 @@ CmBattGetBatteryStatus(IN PCMBATT_DEVICE_EXTENSION DeviceExtension,
             }
         }
     }
-    else if ((DesignVoltage != CM_UNKNOWN_VALUE) && (DesignVoltage))
+    else if ((DesignVoltage != CM_UNKNOWN_VALUE) && (DesignVoltage != 0)) // Same as doing DeviceExtension->BifData.PowerUnit == ACPI_BATT_POWER_UNIT_AMPS
     {
         /* We have voltage data, what about capacity? */
         if (RemainingCapacity == CM_UNKNOWN_VALUE)

drivers/bus/acpi/cmbatt/cmbatt.h

@@ -67,6 +67,13 @@ typedef enum _CMBATT_EXTENSION_TYPE
 #define CM_MAX_VALUE                0x7FFFFFFF
 #define CM_UNKNOWN_VALUE            0xFFFFFFFF
 
+#define CONVERT_MAH_TO_MWH(mA, Volts) (((mA) * (Volts) + 500) / 1000)
+
+#define CONVERT_BATT_INFO(Capacity, DesignVoltage) \
+    (((Capacity) != BATTERY_UNKNOWN_CAPACITY) \
+        ? CONVERT_MAH_TO_MWH((Capacity), (DesignVoltage)) \
+        : BATTERY_UNKNOWN_CAPACITY)
+
 typedef struct _ACPI_BST_DATA
 {
     ULONG State;