Some documentation.

src/main/java/li/cil/oc2/api/API.java

@@ -26,9 +26,4 @@ public final class API {
      * @see Callback
      */
     public static final String IMC_ADD_RPC_METHOD_PARAMETER_TYPE_ADAPTER = "addRPCMethodParameterTypeAdapter";
-
-    ///////////////////////////////////////////////////////////////////
-
-    private API() {
-    }
 }

src/main/java/li/cil/oc2/api/bus/device/DeviceTypes.java

@@ -3,6 +3,9 @@ package li.cil.oc2.api.bus.device;
 import li.cil.oc2.api.API;
 import net.minecraftforge.registries.ObjectHolder;
 
+/**
+ * Lists built-in device types for convenience.
+ */
 @ObjectHolder(API.MOD_ID)
 public final class DeviceTypes {
     @ObjectHolder("memory") public static DeviceType MEMORY = null;

src/main/java/li/cil/oc2/api/bus/device/ItemDevice.java

@@ -2,8 +2,34 @@ package li.cil.oc2.api.bus.device;
 
 import net.minecraft.nbt.CompoundNBT;
 
+/**
+ * Specialized device type provided by {@link li.cil.oc2.api.bus.device.provider.ItemDeviceProvider}s.
+ * <p>
+ * This interface provides methods that allow the context in which an item based device is
+ * created to copy data from and to the {@link net.minecraft.item.ItemStack} the device was
+ * created for.
+ * <p>
+ * By default, no data is copied to and from the {@link net.minecraft.item.ItemStack}. Use
+ * these methods for storing data that should survive the item the device is based on being
+ * removed from the context (e.g. a computer) and being put back in some context.
+ */
 public interface ItemDevice extends Device {
-    void exportToItemStack(CompoundNBT nbt);
+    /**
+     * Export data that should be copied to the {@link net.minecraft.item.ItemStack}
+     * this device was created for to a tag that will be stored in the item.
+     *
+     * @param nbt the tag that will be written to the item.
+     */
+    default void exportToItemStack(final CompoundNBT nbt) {
+    }
 
-    void importFromItemStack(CompoundNBT nbt);
+    /**
+     * Import data that is present on the {@link net.minecraft.item.ItemStack} this
+     * device was created for. The provided tag corresponds to the one presented to
+     * the {@link #exportToItemStack(CompoundNBT)} method.
+     *
+     * @param nbt the tag that was read from the item.
+     */
+    default void importFromItemStack(final CompoundNBT nbt) {
+    }
 }

src/main/java/li/cil/oc2/api/bus/device/object/ObjectDevice.java

@@ -63,6 +63,8 @@ public final class ObjectDevice implements RPCDevice {
         this(object, emptyList());
     }
 
+    ///////////////////////////////////////////////////////////////////
+
     @Override
     public List<String> getTypeNames() {
         return typeNames;

src/main/java/li/cil/oc2/api/bus/device/vm/InterruptAllocator.java

@@ -2,8 +2,29 @@ package li.cil.oc2.api.bus.device.vm;
 
 import java.util.OptionalInt;
 
+/**
+ * Allows reserving interrupts on the primary interrupt controller of a virtual machine
+ * during a {@link VMDevice#load(VMContext)} call.
+ * <p>
+ * Allocated interrupts should be persisted and used in {@link #claimInterrupt(int)}
+ * when restoring from a saved state to ensure correct behaviour of the loaded virtual
+ * machine.
+ */
 public interface InterruptAllocator {
+    /**
+     * Tries to reserve an interrupt with the specified index. The returned interrupt
+     * may differ from the one provided, if the interrupt has already been claimed by
+     * some other device. In this case, the result will be same as calling {@link #claimInterrupt()}.
+     *
+     * @param interrupt the interrupt to claim.
+     * @return the interrupt that was claimed, if any.
+     */
     OptionalInt claimInterrupt(int interrupt);
 
+    /**
+     *
+     *
+     * @return the interrupt that was claimed, if any.
+     */
     OptionalInt claimInterrupt();
 }

src/main/java/li/cil/oc2/api/bus/device/vm/MemoryRangeAllocator.java

@@ -4,8 +4,38 @@ import li.cil.sedna.api.device.MemoryMappedDevice;
 
 import java.util.OptionalLong;
 
+/**
+ * Allows adding {@link MemoryMappedDevice}s to the memory map of a virtual machine
+ * during a {@link VMDevice#load(VMContext)} call.
+ * <p>
+ * Allocated addresses should be persisted and used in {@link #claimMemoryRange(long, MemoryMappedDevice)}
+ * when restoring from a saved state to ensure correct behaviour of the loaded virtual
+ * machine.
+ */
 public interface MemoryRangeAllocator {
+    /**
+     * Tries to add a {@link MemoryMappedDevice} to the memory map at the specified
+     * address. The returned address may differ from the address provided, if the
+     * device cannot fit into the memory map at the specified address. In this case,
+     * the result will be the same as calling {@link #claimMemoryRange(MemoryMappedDevice)}.
+     *
+     * @param address the address to add the specified device at.
+     * @param device  the device to add at the specified address.
+     * @return the address the device was added at, if any.
+     */
     OptionalLong claimMemoryRange(long address, MemoryMappedDevice device);
 
+    /**
+     * Tries to add a {@link MemoryMappedDevice} to the memory map at an address
+     * determined by the virtual machine. This may take into account the type of
+     * device being added. Typically, {@link li.cil.sedna.api.device.PhysicalMemory}
+     * devices will be allocated in a different memory region than regular devices.
+     * <p>
+     * If the device could not fit into the memory map at all, this will return
+     * {@link OptionalLong#empty()}.
+     *
+     * @param device the device to add to the memory map.
+     * @return the address the device was added at, if any.
+     */
     OptionalLong claimMemoryRange(MemoryMappedDevice device);
 }

src/main/java/li/cil/oc2/common/bus/device/AbstractItemDevice.java

@@ -2,20 +2,9 @@ package li.cil.oc2.common.bus.device;
 
 import li.cil.oc2.api.bus.device.ItemDevice;
 import net.minecraft.item.ItemStack;
-import net.minecraft.nbt.CompoundNBT;
 
 public abstract class AbstractItemDevice extends AbstractObjectDevice<ItemStack> implements ItemDevice {
     public AbstractItemDevice(final ItemStack value) {
         super(value);
     }
-
-    ///////////////////////////////////////////////////////////////////
-
-    @Override
-    public void exportToItemStack(final CompoundNBT nbt) {
-    }
-
-    @Override
-    public void importFromItemStack(final CompoundNBT nbt) {
-    }
 }