quantum: util: add bit and bitmask helpers

These helpers are handy and can prevent off-by-one errors when working
with registers and general low level bit manipulation tasks.

quantum/bits.h

@@ -0,0 +1,23 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#pragma once
+
+#define BITS_PER_BYTE 8
+#define BITS_PER_LONG 32
+#define BITS_PER_LONG_LONG 64
+
+#define BIT(nr) (UL(1) << (nr))
+#define BIT_ULL(nr) (ULL(1) << (nr))
+#define BIT_MASK(nr) (UL(1) << ((nr) % BITS_PER_LONG))
+#define BIT_WORD(nr) ((nr) / BITS_PER_LONG)
+#define BIT_ULL_MASK(nr) (ULL(1) << ((nr) % BITS_PER_LONG_LONG))
+#define BIT_ULL_WORD(nr) ((nr) / BITS_PER_LONG_LONG)
+
+/*
+ * Create a contiguous bitmask starting at bit position @l and ending at
+ * position @h. For example
+ * GENMASK_ULL(39, 21) gives us the 64bit vector 0x000000ffffe00000.
+ */
+#define GENMASK(h, l) (((~UL(0)) - (UL(1) << (l)) + 1) & (~UL(0) >> (BITS_PER_LONG - 1 - (h))))
+
+#define GENMASK_ULL(h, l) (((~ULL(0)) - (ULL(1) << (l)) + 1) & (~ULL(0) >> (BITS_PER_LONG_LONG - 1 - (h))))

quantum/util.h

@@ -4,6 +4,7 @@
 
 #pragma once
 
+#include "bits.h"
 #include "bitwise.h"
 
 // convert to string