Document xHCI runtime registers and interrupter registers

src/hulk/usb/xhci.d

@@ -255,11 +255,69 @@ struct XHCI
     }
     static assert(PortRegisters.sizeof == 0x10u);
 
+    /**
+     * Located at offset rts_offset from PCI base address.
+     */
     struct RuntimeRegisters
     {
+        /**
+         * Microframe index. Incremented by controller each microframe.
+         */
         uint mfindex;
+
         uint[7] _reserved01;
-        uint ir;
+
+        /**
+         * Interrupter register sets.
+         */
+        InterrupterRegister[0] ir;
+    }
+
+    /**
+     * Interrupter register set.
+     *
+     * A copy of this register set is present for each interrupter.
+     */
+    struct InterrupterRegister
+    {
+        /**
+         * Interrupter Management Register.
+         * 0 Interrupt Pending (IP)
+         * 1 Interrupt Enable
+         * 31:2 reserved
+         */
+        uint imr;
+
+        /**
+         * Interrupter Moderation.
+         * 15:0 Interrupt Moderation Interval
+         * 31:16 Interrupt Moderation Counter
+         */
+        uint im;
+
+        /**
+         * Event Ring Segment Table Size.
+         * 15:0 Event Ring Segment Table Size
+         * 31:16 reserved
+         */
+        uint ersts;
+
+        uint reserved;
+
+        /**
+         * Event Ring Segment Table Base Address.
+         * 5:0 reserved
+         * 63:6 Event Ring Segment Table Base Address
+         */
+        ulong erstba;
+
+        /**
+         * Event Ring Dequeue Pointer.
+         * 2:0 Dequeue ERST Segment Index
+         * 3 Event Handler Busy
+         * 63:4 Event Ring Dequeue Pointer
+         */
+        ulong erdp;
     }
 
     struct DoorbellRegister