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. The macros themself are inspired by the bits.h macros from the linux kernel source code. Signed-off-by: Stefan Kerkmann <[email protected]> Co-authored-by: Pascal Getreuer <[email protected]>
qmk · Sep 8, 2024 · d640e1f · d640e1f
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diff --git a/quantum/bits.h b/quantum/bits.h
@@ -0,0 +1,29 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#pragma once
+
+#include <stdint.h>
+
+/**
+ *  @brief Mask for the little endian nth bit (0-31) in a 32-bit integer.
+ */
+#define BIT32(n) (UINT32_C(1) << (n))
+
+/**
+ * @brief Mask for the little endian nth bit (0-63) in a 64-bit integer.
+ */
+#define BIT64(n) (UINT64_C(1) << (n))
+
+/**
+ * @brief Create a contiguous 32-bit wide bitmask starting at bit position @l
+ * and ending at position @h. The range is inclusive, meaning GENMASK32(20, 10)
+ * gives us the 32-bit mask 0x001ffc00.
+ */
+#define GENMASK32(h, l) (((~UINT32_C(0)) - (UINT32_C(1) << (l)) + 1) & (~UINT32_C(0) >> (UINT32_WIDTH - 1 - (h))))
+
+/**
+ * @brief Create a contiguous 64-bit wide bitmask starting at bit position @l
+ * and ending at position @h. The range is inclusive, meaning GENMASK64(39, 21)
+ * gives us the 64-bit mask 0x000000ffffe00000.
+ */
+#define GENMASK64(h, l) (((~UINT64_C(0)) - (UINT64_C(1) << (l)) + 1) & (~UINT64_C(0) >> (UINT64_WIDTH - 1 - (h))))
diff --git a/quantum/util.h b/quantum/util.h
@@ -4,6 +4,7 @@
 
 #pragma once
 
+#include "bits.h"
 #include "bitwise.h"
 
 // convert to string