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-rw-r--r--include/bitfield.h58
1 files changed, 58 insertions, 0 deletions
diff --git a/include/bitfield.h b/include/bitfield.h
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index 0000000..ec4815c
--- /dev/null
+++ b/include/bitfield.h
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+/*
+ * Copyright 2013 Broadcom Corporation.
+ *
+ * SPDX-License-Identifier: GPL-2.0+
+ */
+
+/*
+ * Bitfield operations
+ *
+ * These are generic bitfield operations which allow manipulation of variable
+ * width bitfields within a word. One use of this would be to use data tables
+ * to determine how to reprogram fields within R/W hardware registers.
+ *
+ * Example:
+ *
+ * old_reg_val
+ * +--------+----+---+--+-----+----------+
+ * | | | | | old | |
+ * +--------+----+---+--+-----+----------+
+ *
+ * new_reg_val
+ * +--------+----+---+--+-----+----------+
+ * | | | | | new | |
+ * +--------+----+---+--+-----+----------+
+ *
+ * mask = bitfield_mask(10, 5);
+ * old = bitfield_extract(old_reg_val, 10, 5);
+ * new_reg_val = bitfield_replace(old_reg_val, 10, 5, new);
+ *
+ * The numbers 10 and 5 could for example come from data
+ * tables which describe all bitfields in all registers.
+ */
+
+#include <linux/types.h>
+
+/* Produces a mask of set bits covering a range of a uint value */
+static inline uint bitfield_mask(uint shift, uint width)
+{
+ return ((1 << width) - 1) << shift;
+}
+
+/* Extract the value of a bitfield found within a given register value */
+static inline uint bitfield_extract(uint reg_val, uint shift, uint width)
+{
+ return (reg_val & bitfield_mask(shift, width)) >> shift;
+}
+
+/*
+ * Replace the value of a bitfield found within a given register value
+ * Returns the newly modified uint value with the replaced field.
+ */
+static inline uint bitfield_replace(uint reg_val, uint shift, uint width,
+ uint bitfield_val)
+{
+ uint mask = bitfield_mask(shift, width);
+
+ return (reg_val & ~mask) | (bitfield_val << shift);
+}